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Highlights 2011

journal of Physics GNuclear and Particle Physics

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H i g h l i g h t s 2 0 1 1 3

Dear colleagues,

It has been an exciting year for Journal of Physics G: Nuclear and Particle Physics (jPhysG). We have attracted many great papers, topical reviews and focus issues.

In our December issue jPhysG exclusively presented articles from Quark Matter 2011. This was a milestone with a fascinating harvest of LHC heavy-ion data, new results from Brookhaven’s Relativistic Heavy-Ion Collider, as well as a broad range of theoretical highlights.

This year has seen some new features introduced to jPhysG. Our new LabTalk section allows authors to explain the significance of their work to a broader audience, and lets readers get to know the scientists behind the highlighted papers.

In order to provide the broadest visibility for our authors’ work, jPhysG now offers an open-access option. Choosing the open-access option means that anyone, anywhere in the world can access your work, completely free at any time.

In addition, a number of new online features for material in the journal are imminent as part of IOP Publishing’s Article Evolution program. These include a new functionality for viewing articles on IOPscience as a HTML page, as well as tools to make it easier for readers to navigate through an article and view images.

We look forward to building on past successes and continuing to establish jPhysG as a unique journal in the area of nuclear physics, particle physics and in nuclear and particle astrophysics. With jPhysG’s topical reviews and focus issues, we have a unique and flexible format to react to new developments and to highlight key accomplishments, new results and directions.

I would like to kindly thank all of the authors and referees who helped to make this a great year for jPhysG. This brochure provides some highlights of the research in the field over the past year. More can be found on the jPhysG webpage at iopscience.org/jphysg.

Achim Schwenk Editor-in-ChiefJournal of Physics G: Nuclear and Particle Physics

Impact FactOR

1.770*

Journal of Physics GNuclear and Particle Physics

iopscience.org/jphysg

ISSN 0954-3899

Nuclear and Particle PhysicsJournal of Physics G

FOCUS SECTION ON PHYSICS WITH REACCELERATED ISOL BEAMS

PREFACE

020301 Physics with Reaccelerated ISOL BeamsNigel Orr (Guest Editor)

FOCUS SECTION PAPERS

024001 Radioactive ion beam physics at the cyclotron research centre Louvain-la-NeuveMark Huyse and Riccardo Raabe

024002 ISOL science at the Holifield Radioactive Ion Beam FacilityJ R Beene, D W Bardayan, A Galindo Uribarri, C J Gross, K L Jones, J F Liang,W Nazarewicz, D W Stracener, B A Tatum and R L Varner

024003 Physics with reaccelerated radioactive beams at TRIUMF-ISACG C Ball, L Buchmann, B Davids, R Kanungo, C Ruiz and C E Svensson

024004 Nuclear structure and reaction studies at SPIRALA Navin, F de Oliveira Santos, P Roussel-Chomaz and O Sorlin

024005 Physics with REX-ISOLDE: from experiment to facilityP Van Duppen and K Riisager

PAPERS

PARTICLE PHYSICS

025001 Two-loop QCD renormalization and anomalous dimension of the scalar diquark operatorR T Kleiv and T G Steele

025002 Predictions of hadron abundances in pp collisions at the LHCF Becattini, P Castorina, A Milov and H Satz

025003 Radiative corrections to electron–pion scattering revisitedN Kaiser

NUCLEAR PHYSICS

025101 Nuclear energy functional with a surface-peaked effective mass: global propertiesA F Fantina, J Margueron, P Donati and P M Pizzochero

025102 Evolution of the X(5) critical-point symmetry in rotating 176OsX Hao, L H Zhu, X G Wu, C Y He, B Pan, Y Zheng, L L Wang, L Wang, X Q Li, Y Liu,H B Ding, Z Y Li, J F Zhang, H B Sun and G S Li

025103 A diagonalization algorithm revisited and applied to the nuclear shell modelD Bianco, F Andreozzi, N Lo Iudice, A Porrino and F Knapp

025104 Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes andisomersM Avgoulea, Yu P Gangrsky, K P Marinova, S G Zemlyanoi, S Fritzsche, D Iablonskyi,C Barbieri, E C Simpson, P D Stevenson, J Billowes, P Campbell, B Cheal, B Tordoff,M L Bissell, D H Forest, M D Gardner, G Tungate, J Huikari, A Nieminen, H Penttila andJ Aysto

(Continued on inside back cover)

Bibliographic codesCODEN: JPGPED 38 (2) 020301–025201 (2011) ISSN: 0954-3899

Volume 38 Number 2 February 2011

Journal of Physics G Nuclear and Particle Physics

Vol 38, No 2 020301–025201

February 2011

Volume 38 Number 2 February 2011

Focus sectionPhysics with Reaccelerated ISOL BeamsGuest Editor: Nigel Orr

G38-2coverUS.indd 2-4 17/01/2011 14:59

* As listed in ISI®’s 2010 Science Citation Index journal citation reports

Cover image: Contour plots representing various maximum invariant masses of combinations of quarks and leptons N Srimanobhas and B Asavapibhop 2011 J. Phys. G: Nucl. Part. Phys. 38 075001.


4 H i g h l i g h t s 2 0 1 1

Editor-in-chief A Schwenk EMMI/TU Darmstadt, Germany

Deputy Editor A D Martin University of Durham, UK

Editorial Board F Antinori University of Padua, Italy S A Bass Duke University, Durham, NC, USA L Cardman Jefferson Lab, VA, USAj Cizewski Rutgers University, Piscataway, NJ, USA A Covello Università di Napoli, Italy A De Roeck CERN, Switzerland j Dobaczewski University of Warsaw, Poland M T Dova Universidad Nacional de La Plata, Argentina j R Fry University of Liverpool, UK T Han University of Pittsburgh, PA, USAB R Holstein University of Massachusetts, Amherst, USA T Kajino University of Tokyo, Japan T Kodama Universidade Federal do Rio de Janeiro, Brazil K Kubodera University of South Carolina, Columbia, USA j-P Ma Chinese Academy of Sciences, Beijing, China G McLaughlin North Carolina State University, Raleigh, USA

N Orr LPC-Caen, France S Page University of Manitoba, Winnipeg, Canada T Plehn Universität Heidelberg, Germany H Schatz Michigan State University, MI, USA A W Thomas University of Adelaide, Australia C Volpe IPN Orsay, CNRS/IN2P3, France U Wiedemann CERN, SwitzerlandP Woods University of Edinburgh, UKN Xu Lawrence Berkeley National Laboratory, CA, USA Senior advisory panelA B Balantekin University of Wisconsin, Madison, USAA Faessler Universität Tübingen, Germany W Greiner Universität Frankfurt am Main, Germany P Paul State University of New York, Stony Brook, USA L Schroeder Lawrence Berkeley National Laboratory, CA, USA H Stöcker Universität Frankfurt am Main, Germany

Editorial board

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journal scopeJournal of Physics G: Nuclear and Particle Physics publishes articles on theoretical and experimental topics in the physics of elementary particles and fields, intermediate-energy physics and nuclear physics. The nuclear and particle astrophysics section includes experimental and theoretical research in particle astrophysics, neutrino astrophysics and nuclear astrophysics. The journal also welcomes articles from all interface areas between these fields.

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Contents

Measuring supersymmetry with heavy scalars 9Emmanuel Turlay, Remi Lafaye, Tilman Plehn, Michael Rauch and Dirk Zerwas

jet quenching via jet collimation 9Jorge Casalderrey-Solana, José Guilherme Milhano and Urs Achim Wiedemann

Feeding of the elliptic flow by hard partons 9Boris Tomášik and Péter Lévai

Running gluon mass from a Landau gauge lattice QCD propagator 10O Oliveira and P Bicudo

Equivalence of volume and temperature fluctuations in power-law ensembles 10Grzegorz Wilk and Zbigniew Włodarczyk

Probes of multiparticle production at the LHC 10M G Ryskin, A D Martin and V A Khoze

(g − 2)μ and α(M2Z) re-evaluated using new precise data 11

Kaoru Hagiwara, Ruofan Liao, Alan D Martin, Daisuke Nomura and Thomas Teubner

W+jets at CDF: evidence for top quarks 11Tilman Plehn and Michihisa Takeuchi

Rare B decays and Tevatron top-pair asymmetry 11Chuan-Hung Chen, Sandy S C Law and Run-Hui Li

Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes and isomers 12M Avgoulea et al

Radiative corrections to electron–pion scattering revisited 12N Kaiser

Constraining the initial state granularity with bulk observables in Au+Au collisions at √sNN = 200 GeV 12Hannah Petersen, Christopher Coleman-Smith, Steffen A Bass and Robert Wolpert

Measurement of the β–ν correlation coefficient aβν in the β decay of trapped 6He+ ions 13X Fléchard, Ph Velten, E Liénard, A Méry, D Rodríguez, G Ban, D Durand, F Mauger, O Naviliat-Cuncic and J C Thomas

particle physics

Nuclear physics


H i g h l i g h t s 2 0 1 1 7

Nuclear electric quadrupole moment of 9Li using zero-field β-detected NQR 13A Voss et al

Isomeric mirror states as probes for effective charges in the lower pf shell 14R Hoischen et al

Inclusive selection of intermediate-mass-fragment formation modes in the spallation of 136Xe 14P Napolitani, K-H Schmidt and L Tassan-Got

Statistical and dynamical fluctuations in the ratios of higher net-proton cumulants in relativistic heavy-ion collisions 14Lizhu Chen, Xue Pan, Fengbo Xiong, Lin Li, Na Li, Zhiming Li, Gang Wang and Yuanfang Wu

Trap-assisted separation of nuclear states for gamma-ray spectroscopy: the example of 100Nb 14C Rodríguez Triguero et al

Parity violating electron scattering measurements of neutron densities 15Shufang Ban, C J Horowitz and R Michaels

The influence of collective neutrino oscillations on a supernova r process 15Huaiyu Duan, Alexander Friedland, Gail C McLaughlin and Rebecca Surman

Study of the 11C(p, γ) reaction via the indirect d(11C,12N)n transfer reaction 16D W Lee, J Powell, K Peräjärvi, F Q Guo, D M Moltz and Joseph Cerny

Solar neutrino–electron scattering as background limitation for double-beta decay 16N F de Barros and K Zuber

Self-consistent nuclear mean-field models: example Skyrme–Hartree–Fock 16J Erler, P Klüpfel and P-G Reinhard

The cosmological constant puzzle 16Steven D Bass

Challenges of high-pT processes on nuclei 17B Z Kopeliovich and J Nemchik

Determining pseudoscalar meson photoproduction amplitudes from complete experiments 17A M Sandorfi, S Hoblit, H Kamano and T-S H Lee

Structure of scalar mesons and the Higgs sector of strong interaction 18Martin Schumacher

Nuclear and particle astrophysics

topical reviews

)


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The experimental liquid–vapor phase diagram of bulk nuclear matter 18L G Moretto, J B Elliott, L Phair and P T Lake

Physics with REX-ISOLDE: from experiment to facility 19P Van Duppen and K Riisager

Nuclear structure and reaction studies at SPIRAL 19A Navin, F de Oliveira Santos, P Roussel-Chomaz and O Sorlin

ISOL science at the Holifield Radioactive Ion Beam Facility 19J R Beene, D W Bardayan, A Galindo Uribarri, C J Gross, K L Jones, J F Liang, W Nazarewicz, D W Stracener, B A Tatum and R L Varner

Radioactive ion beam physics at the cyclotron research centre Louvain-la-Neuve 20Mark Huyse and Riccardo Raabe

Physics with reaccelerated radioactive beams at TRIUMF-ISAC 20G C Ball, L Buchmann, B Davids, R Kanungo, C Ruiz and C E Svensson

PHENIX highlights 20S Bathe (for the PHENIX Collaboration)

STAR highlights 21Hiroshi Masui (for the STAR Collaboration)

ALICE results from the first Pb–Pb run at the CERN LHC 21J Schukraft (for the ALICE Collaboration)

Recent heavy-ion results with the ATLAS detector at the LHC 21Peter Steinberg (for the ATLAS Collaboration)

Overview of experimental results in Pb–Pb collisions at √sNN = 2.76 TeV by the CMS Collaboration 22Bolek Wyslouch (for the CMS Collaboration)

Focus sections and special issues


H i g h l i g h t s 2 0 1 1 9

Measuring supersymmetry with heavy scalars

Emmanuel Turlay, Remi Lafaye, Tilman Plehn, Michael Rauch and Dirk Zerwas

2011 J. Phys. G: Nucl. Part. Phys. 38 035003

Supersymmetry with heavy scalars is a model where, at the LHC we have to rely on rate measurements to determine the parameters of the underlying new physics. For this example we show how to combine rate measurements with kinematic endpoints properly, taking into account statistical, systematic and theoretical uncertainties. Provided we observe a sizeable number of events, the LHC should be able to determine many model parameters with small enough error bars to, for example, test unification patterns.

particle physics

jPhysG publishes articles on theoretical and experi-mental topics in the physics of elementary particles and fields. Here’s just a small selection of some of the great work we’ve published in this area this year.

We also publish LabTalks – allowing authors to share more of their

insights and methods.

jet quenching via jet collimation

Jorge Casalderrey-Solana, José Guilherme Milhano and Urs Achim Wiedemann


The ATLAS collaboration recently reported strong modifications of dijet properties in heavy ion collisions. In this work, we discuss to what extent these first data constrain already the microscopic mechanism underlying jet quenching. Simple kinematic arguments lead us to identify a frequency collimation mechanism via which the medium efficiently trims away the soft components of the jet parton shower. Through this mechanism, the observed dijet asymmetry can be accommodated with the values of q^ L that lie in the expected order of magnitude.

Schematic illustration of the spatial embedding of a dijet event in a heavy ion collision. In a central Pb+Pb collision, the overlap of the lead ions in the plane transverse to the beam direction fills a region of more than 10 fm diameter with dense QCD matter. The leading jet and its recoil propagate through this matter on the way to the detectors. Compared to typical time scales in QCD, O(10 fm/c) is a very long time scale for interactions between a set of partonic projectiles and the surrounding QCD matter. This allows for strong medium-modifications of jets in heavy ion collisions.

Feeding of the elliptic flow by hard partons

Boris Tomášik and Péter Lévai


We propose that in nuclear collisions at the LHC the elliptic flow may get a contribution from leading hard and semi-hard partons which deposit energy and momentum into the hydrodynamic bulk medium. The crucial effect is that these partons induce wakes which interact and merge if they come together. The contribution to the integrated elliptic flow is estimated with the help of a toy model to about 25% of the observed value and shows strong event-by-event fluctuations.

Illustration of the likeness or unlikeness of two streams to meet. Left: two streams flowing in the out-of-plane direction are likely to meet. Right: as the fireball is elongated out of the reaction plane, two streams which flow in the in-plane direction have more space to pass each other without merging.

DID YOU KNOW?


10 H i g h l i g h t s 2 0 1 1

Running gluon mass from a Landau gauge lattice QCD propagator

O Oliveira and P Bicudo


The interpretation of the Landau gauge lattice gluon propagator as a massive-type bosonic propagator is investigated. Three different scenarios are discussed: (i) an infrared constant gluon mass; (ii) an ultraviolet constant gluon mass; (iii) a momentum-dependent mass. We find that the infrared data can be associated with a massive propagator up to momenta

~500 MeV, with a constant gluon mass of 723(11) MeV, if one excludes the zero momentum gluon propagator from the analysis, or 648(7) MeV, if the zero momentum gluon propagator is included in the data sets. The ultraviolet lattice data are not compatible with a massive-type propagator with a constant mass. The scenario of a momentum-dependent gluon mass gives a decreasing mass with the momentum, which vanishes in the deep ultraviolet region. Furthermore, we show that the functional forms used to describe the decoupling-like solution of the Dyson–Schwinger equations are compatible with the lattice data with similar mass scales.

Equivalence of volume and temperature fluctuations in power-law ensembles

Grzegorz Wilk and Zbigniew Włodarczyk


Relativistic particle production often requires the use of Tsallis statistics to account for the apparently power-like behavior of transverse momenta observed in the data even at a few GeV/c. In such an approach this behavior is attributed to some specific intrinsic fluctuations of the temperature T in the hadronizing system and is fully accounted by the nonextensivity parameter q. On the other hand, it was recently shown that similar power-law spectra can also be obtained by introducing some specific volume fluctuations, apparently without invoking the introduction of Tsallis statistics. We demonstrate that, in fact, when the total energy is kept constant, these volume fluctuations are equivalent to temperature fluctuations and can be derived from them. In addition, we show that fluctuations leading to multiparticle power-law Tsallis distributions

Probes of multiparticle production at the LHC

M G Ryskin, A D Martin and V A Khoze


We discuss how the main features of high-energy ‘soft’ and ‘semihard’ pp collisions may be described in terms of parton cascades and multi-pomeron exchange. The interaction between pomerons produces an effective infrared cutoff, k

sat, by the absorption of low kt partons. This provides the possibility of extending the parton approach, used for ‘hard’ processes, to also describe high-energy soft and semihard interactions. In particular, the presence of the cutoff k

sat, which increases with collider energy, means that the production and hadronization of minijets with pt L ksat are the main source of the soft secondaries. We propose several measurements which can be made at the LHC that can further illuminate our understanding of the mechanism which drives the soft and semihard interactions. We show that the structure of pomeron–pomeron interactions may be studied in double-pomeron-exchange processes and in the pt distributions of secondaries near the edge of large rapidity gaps. The so-called ridge effect is another manifestation of the interaction of two partonic cascades.

Results of fitting the infrared lattice propagators to equation (7) in the range [0, qmax] and for χ2/d.o.f. ≤ 2.0. The filled symbols refer to fits including the zero momentum propagator, while open symbols mean that D(0) was removed from the data sets.

The sensitivity to the parameter q of (a) the correlation function C2(σ, δ) with σ = 6 and (b) the distribution of δ, h(δ), with the error band corresponding to the event multiplicity N = 103.

Schematic sketches of the basic diagram for semi-hard particle production in pp collisions: (a) BFKL-like pomeron exchange; (b) DGLAP-based Monte Carlos, where the hard matrix element has a cutoff k

min(s) tuned to the data; and (c) as in (a), but with the inclusion of enhanced multi-pomeron diagrams (which suppresses parton production at low kt, and hence effectively introduces a dynamically generated cutoff k

sat that depends on both the momentum fraction x+ of the beam and x− of the target).

introduce specific correlations between the considered particles. We then propose a possible way to distinguish the fluctuations in each event from those occurring from event-to-event. This could have applications in the analysis of high density events at LHC (and especially in ALICE).


H i g h l i g h t s 2 0 1 1 11

(g − 2)μ and α(M2Z) re-evaluated

using new precise data

Kaoru Hagiwara, Ruofan Liao, Alan D Martin, Daisuke Nomura and Thomas Teubner


We update our standard model predictions for g − 2 of the muon and for the hadronic contributions to the running of the QED coupling, Δα(5)

had(M2Z). Particular emphasis is put on recent changes in the hadronic

contributions from new data in the 2π channel and from the energy region just below 2 GeV. In particular, for the e+e− → π+π− contribution we include the recent ‘radiative return’ data from KLOE and BaBar. We also include the recent BaBar data on other exclusive channels. We make a detailed study of the effect of replacing the measurements of the inclusive cross section, σ(e+e− → hadrons), by the sum of the exclusive channels in the energy interval 1.43 < √s < 2 GeV, which includes a QCD sum-rule analysis of this energy region. Our favoured prediction for the muon anomalous magnetic moment is (g − 2)/2 = (11 659 182.8 ± 4.9) × 10−10 which is 3.3 σ below the present world-average measurement. We compare our g − 2 value with other recent calculations. Our prediction for the QED coupling, obtained via Δα(5)

had(M2Z) = (276.26 ± 1.38) × 10−4 , is α(M2

Z)−1 = 128.944 ± 0.019.

W+jets at CDF: evidence for top quarks

Tilman Plehn and Michihisa Takeuchi


Recently, an anomaly of W+jet events at large invariant masses has been reported by CDF. Many interpretations as physics beyond the standard model are being offered. We show how such an invariant mass peak can arise from a slight shift in the relative normalization of the top and WW backgrounds.

Rare B decays and Tevatron top-pair asymmetry

Chuan-Hung Chen, Sandy S C Law and Run-Hui Li


The recent Tevatron result on the top quark forward–backward asymmetry, which deviates from its standard model prediction by 3.4σ, has prompted many authors to build new models to account for this anomaly. Among the various proposals, we find that those mechanisms which produce tt- via the t- or u-channel can have a strong correlation to the rare B decays. We demonstrate this link by studying a model with a new charged gauge boson, W'. In terms of the current measurements on B → πK decays, we conclude that the branching ratio for B– → π– K-0 is affected most by the new effects. Furthermore, using the world average branching ratio for the exclusive B decays at the 2σ level, we discuss the allowed values for the new parameters. Finally, we point out that the influence of the new physics effects on the direct CP asymmetry in B decays is insignificant.

Normalized difference between the data sets based on radiative return from KLOE [3, 4] and BaBar [5] and the fit of all data in the 2π channel, as indicated on the plot. The (lilac) band symmetric around zero represents the error band of the fit given by the diagonal elements of the fit’s covariance matrix, with local error inflation as explained in the text, whereas the light (yellow) band indicates the error band of the fit without inflation.

Excess in the mjj distribution above the WV peak, as reported by CDF [1]. The electron and muon decay channels are added.

Contours for the ratio RB as a function of g'2 and mW' here the correspondence of each plot is (a) B− → π − K

–0, (b) B

–

d → π +K−, (c) B− → π0K− and (d) B

–

d → π0 K–0.

In 2011 users downloaded our articles more than

129 000 times.

DID YOU KNOW?

Featured in

Labtalk


12 H i g h l i g h t s 2 0 1 1

Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes and isomers

M Avgoulea, Yu P Gangrsky, K P Marinova, S G Zemlyanoi, S Fritzsche, D Iablonskyi, C Barbieri, E C Simpson, P D Stevenson, J Billowes, P Campbell, B Cheal, B Tordoff, M L Bissell, D H Forest, M D Gardner, G Tungate, J Huikari, A Nieminen, H Penttilä and J Äystö


Collinear laser spectroscopy experiments with the Sc+ transition 3d4s 3D2 → 3d4p 3F3 at λ = 363.1 nm were performed on the 42–46Sc isotopic chain using an ion guide isotope separator with a cooler-buncher. Nuclear magnetic dipole and electric quadrupole moments as well as isotope shifts were determined from the hyperfine structure for five ground states and two isomers. Extensive multi-configurational Dirac–Fock calculations were performed in order to evaluate the specific mass-shift, M

SMS, and field-shift, F, parameters which allowed evaluation of the charge radii trend of the Sc isotopic sequence. The charge radii obtained show systematics more like the Ti radii, which increase towards the neutron shell closure N = 20, than the symmetric parabolic curve for Ca. The changes in mean-square charge radii of the isomeric states relative to the ground states for 44Sc and 45Sc were also extracted. The charge radii difference between the ground and isomeric states of 45Sc is in agreement with the deformation effect estimated from the B(E2) measurements but is smaller than the deformation extracted from the spectroscopic quadrupole moments.

Constraining the initial state granularity with bulk observables in Au+Au collisions at √sNN = 200 GeV

Hannah Petersen, Christopher Coleman-Smith, Steffen A Bass and Robert Wolpert


In this paper we conduct a systematic study of the granularity of the initial state of hot and dense QCD matter produced in ultra-relativistic heavy-ion collisions and its influence on bulk observables like particle yields, mT spectra and elliptic flow. For our investigation we use a hybrid transport model, based on (3+1)D hydrodynamics and a microscopic Boltzmann transport approach. The initial conditions are generated by a non-equilibrium hadronic transport approach and the size of their fluctuations can be adjusted by defining a Gaussian smoothing parameter σ. The dependence of the hydrodynamic evolution on the choices of σ and tstart is explored by means of a Gaussian emulator. To generate particle yields and elliptic flow that are compatible with experimental data the initial state parameters are constrained to be σ = 1 fm and tstart = 0.5 fm. In addition, the influence of changes in the equation of state is studied and the results of our event-by-event calculations are compared to a calculation with averaged initial conditions. We conclude that even though the initial state parameters can be constrained by yields and elliptic flow, the granularity needs to be constrained by other correlation and fluctuation observables.

Nuclear physics

We've published some excellent papers on Nuclear Physics this year. Here’s a taster of some of that work. Don’t forget there’s much more online at iopscience.org/jphysg.

Example of a resonance fluorescence spectrum for 44g,mSc. The fitted structure is shown overlaid, with the separate ground state (dashed) and isomeric (dot-dashed) components underneath. Hyperfine F

l → Fu transitions are indicated, with isomeric components denoted by an asterisk (∗). Other spectra (not shown) with overlapping scan regions were also taken and analysed simultaneously. Spectra for the other isotopes are contained in [16].

Featured in

Labtalk

Radiative corrections to electron–pion scattering revisited

N Kaiser


We calculate in closed analytical form the one-loop radiative corrections to electron–pion scattering e−π− → e−π−. Concise expressions (in terms of dimensionless Mandelstam variables) are given for the pertinent interference terms between the tree diagram and the one-loop diagrams related to photonic vertex correction, vacuum polarization and two-photon exchange. Infrared finiteness of these virtual radiative corrections is achieved (in the standard way) by including soft-photon radiation below an energy cutoff λ. We evaluate the finite part of the soft-photon correction factor in the center-of-mass frame. For all contributions we keep the full dependence on the electron mass. The results for the loop amplitudes can also be applied to pion-pair production e−e+ → π+π−. The radiative corrections to the corresponding total cross section are calculated with consideration of the pion structure via a vector meson dominance form factor. We find that such an additional charge form factor (inserted into the photonic vertex correction of the pion) changes the radiative corrections to the total cross section by about −0.2%.

Two-photon exchange diagrams (III), (IV) and (V) for electron–pion scattering.

Featured in

Labtalk


H i g h l i g h t s 2 0 1 1 13

Measurement of the β–ν correlation coefficient aβν in the β decay of trapped 6He+ ions

X Fléchard, Ph Velten, E Liénard, A Méry, D Rodríguez, G Ban, D Durand, F Mauger, O Naviliat-Cuncic and J C Thomas


We have measured the β-ν angular correlation in the β decay of 6He+ ions using a transparent Paul trap. The 6He+ ions, produced at GANIL, were first cooled and bunched before being injected in the LPCTrap setup. The angular correlation was inferred from the time of flight of recoil nuclei detected in coincidence with the β particles. The detection system gives access to the full β decay kinematics, providing means to check the data reliability and to reject a large fraction of background. We find aβν = −0.3335(73)stat(75)syst, in agreement with the standard model

prediction for a pure Gamow–Teller transition.

Nuclear electric quadrupole moment of 9Li using zero-field β-detected NQR

A Voss, M R Pearson, J Billowes, F Buchinger, K H Chow, J E Crawford, M D Hossein, R F Kiefl, C D P Levy, W A MacFarlane, E Mané, G D Morris, T J Parolin, H Saadaoui, Z Salman, M Smadella, Q Song and D Wang


A β-detected nuclear quadrupole resonance (NQR) spectrometer becomes a powerful tool to study changes in nuclear ground-state properties along isotopic chains when coupled to a laser excitation beamline to polarize the nuclei of interest. Recently, the β-NQR technique in a zero magnetic field has been applied for the first time to measure the ratio of static nuclear quadrupole moments of 8, 9Li, Q9/Q8 = 0.966 75(9) denoted by Q8 for 8Li and Q

9 for 9Li, respectively. This shows agreement with present literature values but with significantly improved precision. Based on the literature, the quadrupole moment for 8Li has been re-evaluated to be |Q8| = 32.6(5) mb. From this, the quadrupole moment for 9Li is calculated as |Q9| = 31.5(5) mb with the error being dominated by the error of Q

8.

Emulated number of pions at midrapidity (|y| < 0.5) for central (b < 3.4 fm) Au+Au collisions at √s

NN = 200 GeV in the two-dimensional parameter space of σ and tstart.

Example of a GEANT4 visualization of the detection chamber.

The implantation region outside the cryostat showing (1) the beam direction, (2) three sets of Helmholtz coils for field zeroing, (3) the L scintillator detectors (4) and the light guides from (3) to the photomultiplier (5).

Image tools — zoom and export for PowerPointYou can zoom in and out of an image to study complex structures. You can also export figures to PowerPoint

slides for use in presentations.


14 H i g h l i g h t s 2 0 1 1

Statistical and dynamical fluctuations in the ratios of higher net-proton cumulants in relativistic heavy-ion collisions

Lizhu Chen, Xue Pan, Fengbo Xiong, Lin Li, Na Li, Zhiming Li, Gang Wang and Yuanfang Wu


With the help of transport and statistical models, we find that the ratios of higher net-proton cumulants measured at RHIC are dominated by Poisson-like statistical fluctuations. A way to eliminate this statistical fluctuation is suggested. The obtained dynamical ratios of higher net-proton cumulants are demonstrated to be more relevant to the underlying physics, i.e. the correlations between proton and antiproton, or the critical fluctuations.

Inclusive selection of intermediate-mass-fragment formation modes in the spallation of 136Xe

P Napolitani, K-H Schmidt and L Tassan-Got


A correlation between the production and kinematic properties of the fragments issued from fission and multifragmentation is established in the study of the reaction 136Xe + hydrogen at 1 GeV per nucleon, measured in inverse kinematics at the FRagment Separator (GSI, Darmstadt). Such observables are analysed in a comprehensive study, selected as a function of the decay mode, and related to the isotopic properties of the fragments in the intermediate-mass region. Valuable information can be deduced on the characteristics of the heaviest product in the reaction, which has been considered a fundamental observable for tagging the thermodynamic properties of finite nuclear systems.

Trap-assisted separation of nuclear states for gamma-ray spectroscopy: the example of 100Nb

C Rodríguez Triguero, A M Bruce, T Eronen, I D Moore, M Bowry, A M Denis Bacelar, A Y Deo, V-V Elomaa, D Gorelov, J Hakala, A Jokinen, A Kankainen, P Karvonen, V S Kolhinen, J Kurpeta, T Malkiewicz, P J R Mason, H Penttilä, M Reponen, S Rinta-Antila, J Rissanen, A Saastamoinen, G S Simpson and J Äystö


Low-lying levels in 100Mo are known to be populated by beta decay from both the ground and isomeric states in 100Nb. The small energy difference (~3 ppm) between the two parent states and the similarity of their half-lives make it difficult to distinguish experimentally between the two decay paths. A new technique for separating different states of nuclei has recently been developed in a series of experiments at the IGISOL facility, using the jYFLTRAP installation, at the University of jyväskylä where mass resolution ~2 ppm was achieved in mass measurements and in the production of 133mXe. This paper reports on the extension of this technique to allow the separate study of the gamma-ray decay of levels populated by the different parent states.

Centrality dependence of dynamical skewness (left) and kurtosis (right) for Au + Au collisions at 200 GeV, given by transport models (AMPT and UrQMD) and a statistical model (Therminator).

A schematic of the beta decay of the isomeric and ground states in 100Nb into 100Mo. Beta-decay intensities are from [9]; dashed levels indicate feeding intensities <3%.

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Labtalk

Isomeric mirror states as probes for effective charges in the lower pf shell

R Hoischen, D Rudolph, H L Ma, P Montuenga, M Hellström, S Pietri, Zs Podolyák, P H Regan, A B Garnsworthy, S J Steer, F Becker, P Bednarczyk, L Cáceres, P Doornenbal, J Gerl, M Górska, J Grebosz, I Kojouharov, N Kurz, W Prokopowicz, H Schaffner, H J Wollersheim, L-L Andersson, L Atanasova, D L Balabanski, M A Bentley, A Blazhev, C Brandau, J R Brown, C Fahlander, E K Johansson and A Jungclaus


Following the fragmentation of a 550 MeV u−1 primary beam of 58Ni, time- and energy-correlated γ decays from isomeric states in neutron-deficient nuclei in the 1f

7/2 shell have been identified using the GSI fragment separator in combination with the RISING Ge-detector array. The results on isomers in the mirror pairs 43

22Ti21–4321Sc22 (I

π = 3/2+ and 19/2−), 4524Cr21–

4521Sc24

(Iπ = 3/2+) and 4523V22–

4522Ti23 (I

π = 3/2−) are discussed in the framework of large scale pf and sdpf shell-model calculations, the former in conjunction with isospin symmetry breaking effects with emphasis on effective charges.

Identification plot of N ≤ Z nuclides produced in the fragmentation of a 58Ni beam on a 9Be target. The proton number, Z, is plotted versus the mass-over-charge ratio, A/Z, for fragments, which passed the FRS and its full suite of tracking, time-of-flight and energy loss detection systems.


H i g h l i g h t s 2 0 1 1 15

Parity violating electron scattering measurements of neutron densities

Shufang Ban, C J Horowitz and R Michaels


Parity violating electron scattering allows model-independent measurements of neutron densities that are free from most strong interaction uncertainties. In this paper, we present statistical error estimates for a variety of experiments. The neutron radius Rn can be measured in several nuclei, as long as the nuclear excited states are not too low in energy. We present error estimates for Rn measurements in 40Ca, 48Ca, 112Sn, 120Sn, 124Sn and 208Pb. In general, we find that the smaller the nucleus, the easier the measurement. This is because smaller nuclei can be measured at higher momentum transfers where the parity violating asymmetry A

pv is larger. Also in general, the more neutron rich the isotope, the easier the measurement, because neutron-rich isotopes have larger weak charges and larger A

pv. Measuring Rn in 48Ca appears very promising because it has a higher figure of merit than 208Pb. In addition, Rn(

48Ca) may be more easily related to two-nucleon and three-nucleon interactions, including very interesting three-neutron forces, than Rn(

208Pb). After measuring Rn, one can constrain the surface thickness of the neutron density an with a second measurement at somewhat higher momentum transfers. We present statistical error estimates for measuring an in 48Ca, 120Sn and 208Pb. Again, we find that an is easier to measure in smaller nuclei.

The influence of collective neutrino oscillations on a supernova r process

Huaiyu Duan, Alexander Friedland, Gail C McLaughlin and Rebecca Surman


Recently, it has been demonstrated that neutrinos in a supernova oscillate collectively. This process occurs much deeper than the conventional matter-induced Mikheyev–Smirnov–Wolfenstein effect and hence may have an impact on nucleosynthesis. In this paper we explore the effects of collective neutrino oscillations on the r-process, using representative late-time neutrino spectra and outflow models. We find that accurate modeling of the collective oscillations is essential for this analysis. As an illustration, the often-used ‘single-angle’ approximation makes grossly inaccurate predictions for the yields in our setup. With the proper multiangle treatment, the effect of the oscillations is found to be less dramatic, but still significant. Since the oscillation patterns are sensitive to the details of the emitted fluxes and the sign of the neutrino mass hierarchy, so are the r-process yields. The magnitude of the effect also depends sensitively on the astrophysical conditions—in particular on the interplay between the time when nuclei begin to exist in significant numbers and the time when the collective oscillation begins. A more definitive understanding of the astrophysical conditions, and accurate modeling of the collective oscillations for those conditions, is necessary.

Sensitivity of the parity violating asymmetry Apv for 208Pb to changes in the neutron surface thickness an, see equation (11), where εan = ∈an = d ln Apv /d ln an versus scattering angle θ at beam energies of 1.05 GeV (solid line) and 1.8 GeV (dashed line). The SLY4 neutron density was used.

Temperature T9 as a function of radius in km (dashed line) for two sample thermodynamic

trajectories, one with lower density and s/k = 300 (dot-dashed line), and the other with higher density and s/k = 200 (dashed line); the horizontal bands show the approximate temperature ranges for each stage of the nucleosynthesis as labeled. The solid line shows a sample electron neutrino survival probability P(e) for 20 MeV neutrinos, as calculated assuming an inverted hierarchy. For the trajectory with the early-type density profile, the flavor transformations occur during alpha particle formation, while for the trajectory with the late-type density profile the flavor transformations occur later, during the r-process seed assembly.

Nuclear and particle astrophysics

The Nuclear and Particle Astrophysics section includes experimental and theoretical research in particle astrophysics, neutrino astrophysics and nuclear astrophysics.


16 H i g h l i g h t s 2 0 1 1

Study of the 11C(p, γ) reaction via the indirect d(11C,12N)n transfer reaction

D W Lee, J Powell, K Peräjärvi, F Q Guo, D M Moltz and Joseph Cerny


The 11C(p,γ)12N reaction is expected to be an important branch point in supermassive low-metallicity stars because it could produce CNO seed nuclei before the traditional triple-α process turns on. In this work, the d(11C,12N)n transfer reaction was employed to evaluate this reaction using a radioactive ion beam of 150 MeV 11C with 6 × 105 ions s−1 on target from the BEARS project at the 88 inch cyclotron at the Lawrence Berkeley National Laboratory. Excellent agreement was obtained between the experimental cross sections (θc.m. = 10.9–71.5°) and DWBA calculations. The asymptotic normalization coefficient was deduced to be (C

eff

12N)2 = C12Np1/2)

2 + (C

12Np3/2)

2 = 1.83 ± 0.27 fm–1.

Solar neutrino–electron scattering as background limitation for double-beta decay

N F de Barros and K Zuber


The background on double-beta decay searches due to elastic electron scattering of solar neutrinos of all double-beta emitters with Q-value larger than 2 MeV is calculated, taking into account survival probability and flux uncertainties of solar neutrinos. This work determines the background level to be 1 − 2 × 10−7 counts keV−1 kg−1 yr−1, depending on the precise Q-value of the double-beta emitter. It is also shown that the background level increases dramatically if going to lower Q-values. Furthermore, studies are carried out for various detector systems under consideration for next-generation experiments. It was found that experiments based on loaded liquid scintillator have to expect a higher background. Within the given nuclear matrix element uncertainties any approach exploring the normal hierarchy has to face this irreducible background, which is a limitation on the minimal achievable background for purely calorimetric approaches. Large scale liquid scintillator experiments might encounter this problem already while exploring the inverted hierarchy. Potential caveats by using more sophisticated experimental setups are also discussed.

Self-consistent nuclear mean-field models: example Skyrme–Hartree–Fock

J Erler, P Klüpfel and P-G Reinhard


We review recent developments in the Skyrme–Hartree–Fock (SHF) approach for a self-consistent description of nuclear ground-state properties and dynamics. A brief summary of the Skyrme energy functional and additional ingredients (pairing, Coulomb, center-of-mass correction) is given. Strategies for phenomenological calibration of the SHF functional are discussed. Applications to a variety of observables are presented: the bulk properties of nuclei (energy, charge radius, surface thickness), the impact of information on neutron radii, extrapolation to super-heavy elements and fission stability thereof, isotopic shifts of radii, odd nuclei and associated single-nucleon spectra, low-lying surface vibrations together with the ground-state correlations associated with them, and giant resonances (electric as well as magnetic modes).

The cosmological constant puzzle

Steven D Bass


The accelerating expansion of the Universe points to a small positive vacuum energy density and negative vacuum pressure. A strong candidate is the cosmological constant in Einstein’s equations of general relativity. Possible contributions are zero-point energies and the condensates associated with spontaneous symmetry breaking. The vacuum energy density extracted from astrophysics is 1056 times smaller than the value expected from quantum fields and standard model particle physics. Is the vacuum energy density time dependent? We give an introduction to the cosmological constant puzzle and ideas how to solve it.

A two-dimensional particle identification spectrum from ΔE−E coincidences at the second strip plotted as ΔE versus total energy (= ΔE + E). The 12N gate is shown above the scattered 11C beam. Note that 12C also appears from the d(11C,12C)p reaction.

Systematic of fission and α-decay lifetimes calculated with the Skyrme force SV-min.

topical reviews

Our Topical Reviews are commissioned by our Editorial Board and cover some of the most important subjects in nuclear physics, particle physics, and nuclear and particle astrophysics. The reviews have always proved to be very popular and are a great way to stay up to date on developments in the field.


H i g h l i g h t s 2 0 1 1 17

Challenges of high-pT processes on nuclei

B Z Kopeliovich and J Nemchik


We present an attempt at a critical overview of the current status of modeling for high-pT processes in nuclei. This review covers several topics including coherence phenomena, in particular gluon shadowing and CGC; nuclear effects related to the restrictions imposed by energy conservation at large xL and xT; spacetime development of hadronization of highly virtual light and heavy partons and the related time scales; and the role of early production and subsequent attenuation of pre-hadrons in a dense medium. We identify several intriguing problems in the current paradigms for high-pT processes and propose solutions for some of them.

Determining pseudoscalar meson photoproduction amplitudes from complete experiments

A M Sandorfi, S Hoblit, H Kamano and T-S H Lee


A new generation of complete experiments is focused on a high precision extraction of pseudoscalar meson photoproduction amplitudes. Here, we review the development of the most general analytic form of the cross section, dependent upon the three polarization vectors of the beam, target and recoil baryon, including all single-, double- and triple-polarization terms involving 16 spin-dependent observables. We examine the different conventions that have been used by different authors, and we present expressions that allow the direct numerical calculation of any pseudoscalar meson photoproduction observables with arbitrary spin projections from the Chew–Goldberger–Low–Nambu amplitudes. We use this numerical tool to clarify apparent sign differences that exist in the literature, in particular with the definitions of six double-polarization observables. We also present analytic expressions that determine the recoil baryon polarization, together with examples of their potential use with quasi-4π detectors to deduce observables. As an illustration of the use of the consistent machinery presented in this review, we carry out a multipole analysis of the γp → K+Λ reaction and examine the impact of recently published polarization measurements. When combining data from different experiments, we utilize the Fierz identities to fit a consistent set of scales. In fitting multipoles,

Top: pA collision in which the colliding proton is excited by multiple interactions up to the saturated scale Q2

sA, which leads to an increased multiplicity of soft gluons in the incoming proton. Bottom: nuclear collision in which participating nucleons on both sides are boosted to the saturation scales, Q2

sA in the nucleus B, and Q2

sB in the nucleus A. As a result, the low-x gluon population is enriched in both nuclei.

Cx' (left) and Cz' (right) for the γp → K+ K reaction at W = 1680 MeV (top) and W = 1940 MeV (bottom). Kaon-MAID predictions are dashed (black) [23–25], SAID predictions are dotted (black) [26, 27], BoGa predictions are dot–dashed (blue) [28] and predictions from jSLT [29] are solid (blue). The green circles are from [20].

we use a combined Monte Carlo sampling of the amplitude space, with gradient minimization, and find a shallow χ2 valley pitted with a very large number of local minima. This results in broad bands of multipole solutions that are experimentally indistinguishable. While these bands have been noticeably narrowed by the inclusion of new polarization measurements, many of the multipoles remain very poorly determined, even in sign, despite the inclusion of data on eight different observables. We have compared multipoles from recent PWA codes with our model-independent solution bands and found that such comparisons provide useful consistency tests which clarify model interpretations. The potential accuracy of amplitudes that could be extracted from measurements of all 16 polarization observables has been studied with mock data using the statistical variations that are expected from ongoing experiments. We conclude that, while a mathematical solution to the problem of determining an amplitude free of ambiguities may require eight observables, as has been pointed out in the literature, experiments with realistically achievable uncertainties will require a significantly larger number.

Share linksA set of links next to the article title on IOPscience enables you to export article details to a variety of popular social

networking and bookmarking sites.


18 H i g h l i g h t s 2 0 1 1

Structure of scalar mesons and the Higgs sector of strong interaction

Martin Schumacher


The scalar mesons σ(600), κ(800), f0(980) and a0(980) together with the pseudo Goldstone bosons π, K and η may be considered as the Higgs sector of strong interaction. After a long time of uncertainty about the internal structure of the scalar mesons there now seems to be consistency which is in line with the major parts of experimental observations. Great progress has been made by introducing the unified model of Close and Törnqvist. This model states that scalar mesons below 1 GeV may be understood as q2q–2 in S-wave with some qq– in P-wave in the center, further out they rearrange as (qq–)2 and finally as meson–meson states. The P-wave component inherent in the structure of the neutral scalar mesons can be understood as a doorway state for the formation of the scalar meson via two-photon fusion, whereas in nucleon Compton scattering these P-wave components serve as intermediate states. The masses of the scalar mesons are predicted in terms of spontaneous and explicit symmetry breaking.

The experimental liquid–vapor phase diagram of bulk nuclear matter

L G Moretto, J B Elliott, L Phair and P T Lake


The modern investigation of clusters, for which 1 << N << ∞, requires a generalization of the thermodynamics developed for infinite systems. For instance, in finite systems, phase transitions and phase coexistence become ill-defined with ambiguous signals. The existence of phase transitions in nuclear systems, in particular of the liquid–vapor kind, has been widely discussed and even experimentally claimed. A consistent and unambiguous approach to this problem requires a connection between finite systems and the corresponding infinite systems. Historically, this has been achieved at temperature T = 0 by the introduction of the liquid drop model and the extraction of the volume term, which is a fundamental quantity of nuclear matter. This work extends this approach to T > 0, by

Left panel: spontaneous symmetry breaking in the chiral limit illustrated by the LσM: in the SU(2) sector there is one ‘strong Higgs boson’, the σ meson having a mass of mcl

σ = 652 MeV taking part in spontaneous symmetry breaking, accompanied by an isotriplet of massless π mesons serving as Goldstone bosons. In the SU(3) sector there are eight massless Goldstone bosons π, K, η, and nine scalar mesons σ, κ, f 0 and a0, all of them having the same mass as the σ meson in the chiral limit. The mass degeneracy is removed by explicit symmetry breaking. Right panel: tadpole graphs of chiral symmetry breaking. (a) Four-fermion version of the Nambu–jona–Lasinio (NjL) model; (b) bosonized NjL model.

A realization of a Lennard-jones simulation showing a drop (the large cluster at midheight and toward the right) in equilibrium with a vapor (the monomers, dimers, trimers, etc surrounding the drop). The gray spheres show the particles. Clusters are shown by particles connected with gray cylinders.

determining the liquid–vapor coexistence line and its termination at the critical point. Since there is no known experimental situation where a nuclear liquid and vapor are in coexistence, we establish a relationship between evaporation rates and saturated vapor concentration and characterize the saturated vapor with Fisher’s droplet model. We validate this approach by analyzing cluster concentrations in the Ising and Lennard-jones models and extracting the corresponding first-order coexistence line and critical temperature. Since the vapor of clusters coexists with a finite liquid drop, we devise a finite size correction leading to a modified Fisher equation. The application of the above techniques to nuclear systems requires dealing also with the Coulomb force. Nuclear cluster evaporation rates can be corrected for Coulomb effects and can be used to evaluate the cluster concentrations in the ‘virtual’ equilibrium vapor. These cluster concentrations, determined over a wide temperature range, can be analyzed by means of a modified Fisher formula. This leads to the extraction of the entire liquid–vapor coexistence line terminating at the critical point. A large body of experimental data has been analyzed in this manner and the liquid–vapor phase diagram of nuclear matter has been extracted.

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H i g h l i g h t s 2 0 1 1 19

The layout of the ISOLDE facility is shown. The REX-ISOLDE accelerator complex can receive RIB from both mass separators (HRS: high resolution separator, GPS: general purpose separator). Two beam ports are currently available for experiments with the energetic beams.

The VAMOS at GANIL showing (from left to right) the two large quadrupoles, Wein filter, dipole and part of the focal plane detection chamber.

Scanning electron micrograph of the RVC matrix before and after a coating of uranium dicarbide has been deposited.

Physics with REX-ISOLDE: from experiment to facility

P Van Duppen and K Riisager


The REX-ISOLDE project and its physics program are presented. The innovative approach used to post-accelerate essentially all existing radioactive beams available at ISOLDE to 3 MeV u−1 is presented and beam properties are discussed. Isotopes as light as 8Li and as heavy as 224Ra have been used for Coulomb excitation, few-nucleon transfer reaction or fusion evaporation studies. Selected examples of the physics program, primarily utilizing the Miniball detector and segmented silicon detector arrays, are presented emphasizing some unique features of REX-ISOLDE. Finally, the HIE-ISOLDE project aiming at, amongst other goals, increasing the beam energy to 5.5 MeV u−1 and above, will be briefly discussed.

Nuclear structure and reaction studies at SPIRAL

A Navin, F de Oliveira Santos, P Roussel-Chomaz and O Sorlin


The SPIRAL facility at GANIL, operational since 2001, is described briefly. The diverse physics program using the re-accelerated (1.2–25 MeV/u) beams ranging from He to Kr and the instrumentation specially developed for their exploitation are presented. Results of these studies, using both direct and compound processes, addressing various questions related to the existence of exotic states of nuclear matter, evolution of new ‘magic numbers’, tunnelling of exotic nuclei, neutron correlations, exotic pathways in astrophysical sites and characterization of the continuum, are discussed. The future prospects for the facility and the path towards SPIRAL2, a next generation ISOL facility, are also briefly presented.

ISOL science at the Holifield Radioactive Ion Beam Facility

J R Beene, D W Bardayan, A Galindo Uribarri, C J Gross, K L Jones, J F Liang, W Nazarewicz, D W Stracener, B A Tatum and R L Varner


The Holifield Radioactive Ion Beam Facility (HRIBF) provides high-quality Isotope Separator Online beams of short-lived, radioactive nuclei for nuclear structure and reaction studies, astrophysics research, and interdisciplinary applications. The primary driver, the Oak Ridge Isochronous Cyclotron, produces rare isotopes by bombarding highly refractory targets with light ions. The radioactive isotopes are ionized, formed into a beam, mass selected, injected into the 25 MV tandem, accelerated, and used in experiments. This paper reviews the HRIBF and its users’ science.

Focus sections and special issues

jPhysG’s focus sections are a collection of papers on a topic of considerable interest. This year we published a great focus section on physics with reaccelerated ISOL beams, and were also able to exclusively publish the proceedings of Quark Matter 2011. Below we’ve included a taster of some of this fascinating work.


20 H i g h l i g h t s 2 0 1 1

Radioactive ion beam physics at the cyclotron research centre Louvain-la-Neuve

Mark Huyse and Riccardo Raabe


The first beam of post-accelerated radioactive ions was realized in 1989 at the Louvain-la-Neuve research facility. The method employed two coupled cyclotrons to produce, separate and re-accelerate the species of interest. Several technological challenges were solved in the process to obtain pure and intense beams for the use in nuclear physics research. Similarly, new techniques were developed and refined for the measurement of the nuclear reactions induced by the radioactive beams. The available energy range made the facility particularly suited for nuclear astrophysics studies, and important results were obtained in the determination of stellar reaction rates using beams of 7Be, 13N, 18F and 18, 19Ne. A beam of 6He ions was extensively used in studies of the nuclear structure (halos, molecular states) and dynamics (the reaction process at energies around the potential barrier).

Physics with reaccelerated radioactive beams at TRIUMF-ISAC

G C Ball, L Buchmann, B Davids, R Kanungo, C Ruiz and C E Svensson


The TRIUMF-ISAC radioactive beam facility provides reaccelerated beams in the energy range from 0.15 to 5 A MeV for A < 30 to a full suite of world class experimental apparatus, enabling a forefront research program focused on understanding the evolution of nuclear structure towards the limits of existence and the origin of the chemical elements in the universe. Recent ISAC science highlights and future objectives are presented.

PHENIX highlights

S Bathe (for the PHENIX Collaboration)


Results from RHIC led to the discovery of the strongly coupled quark–gluon plasma (sQGP), a state of the QCD vacuum. In order to arrive at a coherent picture of this state, both the properties of the sQGP and the conditions under which the sQGP is measured have to be established. In this paper, we present recent experimental results of the PHENIX Collaboration, further constraining the conditions and the properties of the sQGP at RHIC: measurement of direct photon elliptic flow provides strong constraints for hydrodynamic models employed to derive the initial temperature; measurement of v

2 and v3 disentangles effects from the initial state and η/s; flow and RAA measurements at lower √s extend the results to a regime at lower temperature and higher baryon density.

Portion of the chart of nuclei, with indication of the paths of the hot-CNO cycle (Hot-CNO I) and very-hot-CNO cycle (Hot-CNO II), with the possible escape routes. The reactions studied in Louvain-la-Neuve are highlighted.

The TIGRESS γ -ray spectrometer in an early-implementation configuration at ISAC-II consisting of eight HPGe clover detectors.

Schematic phase diagram of QDC matter. The conditions under which the sQGP is measured are listed on the left; the properties are listed on the right. The arrows point to the approximate region of phase space in terms of net baryon density and temperature indicated by the data.


H i g h l i g h t s 2 0 1 1 21

STAR highlights

Hiroshi Masui (for the STAR Collaboration)


We report selected results from STAR collaboration at the RHIC, focusing on jet–hadron and jet-like correlations, quarkonium suppression and collectivity, di-electron spectrum in both p+p and Au+Au, and higher moments (standard deviation, skewness and kurtosis) of net-protons as well as azimuthal anisotropy from the RHIC Beam Energy Scan program.

Recent heavy-ion results with the ATLAS detector at the LHC

Peter Steinberg (for the ATLAS Collaboration)


Results are presented from the ATLAS collaboration from the 2010 LHC heavy-ion run, during which nearly ten inverse microbarns of luminosity were delivered. Soft physics results include charged particle multiplicities and collective flow. The charged particle multiplicity, which tracks initial state entropy production, increases by a factor of 2 relative to the top RHIC energy, with a centrality dependence very similar to that already measured at the RHIC. Measurements of elliptic flow out to large transverse momentum also show similar results to what was measured at the RHIC, but no significant pseudorapidity dependence. Extensions of these measurements to higher harmonics have also been made and can be used to explain structures in the two-particle correlation functions that had long been attributed to jet–medium interactions. New hard probe measurements include single muons, jets and high p

T hadrons. Single muons at high momentum are used to extract the yield of W± bosons and are found to be consistent within statistical uncertainties with binary collision scaling. Conversely, jets are found to be suppressed in central events by a factor of 2 relative to peripheral events, with no significant dependence on the jet energy. Fragmentation functions are also found to be the same in central and peripheral events. Finally, charged hadrons have been measured out to 30 GeV, and their centrality dependence relative to peripheral events is similar to that found for jets.

ALICE results from the first Pb–Pb run at the CERN LHC

J Schukraft (for the ALICE Collaboration)


After 20 years of preparation, the dedicated heavy-ion experiment ALICE, which stands for A Large Ion Collider Experiment, took first data at the CERN LHC accelerator with proton collisions at the end of 2009 and with lead beams at the end of 2010. This paper will give a brief overview of the main results presented at the Quark Matter 2011 conference.

Di-electron mass spectrum in p+p collisions at √s = 200 GeV after combinatorial background subtraction. The solid circles show the data, the bars denote the statistical uncertainties and the boxes around data points show systematic uncertainties. The dashed lines represent the individual hadronic source used in the cocktail simulations. The bottom panels show the ratio of data to cocktail simulation, where shaded bands around unity and the boxes around data points show the systematic uncertainties on cocktail and data, respectively.

ALICE uses 18 different detector systems, indicated in the figure with their acronyms. The central detectors are located inside the L3 magnet (left side), the forward muon arm spectrometer is located on the right and the insert top right is a blow-up of the interaction region showing the six layers of the silicon vertex detector (ITS) and the forward trigger and multiplicity detectors (T0, V0, FMD).

Schematic diagram of the ATLAS detector, showing the three main subsystems:the inner detector (|η| < 2.5), the calorimeter (|η| < 4.9) and the muon spectrometer (|η| < 2.7).

All articles are free to read for 30 days after publication, including topical reviews.

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Overview of experimental results in Pb–Pb collisions at √sNN = 2.76 TeV by the CMS Collaboration

Bolek Wyslouch (for the CMS Collaboration)


The CMS experiment at the LHC is a general-purpose apparatus with a set of large acceptance and high granularity detectors for hadrons, electrons, photons and muons, providing unique capabilities for both proton–proton and ion–ion collisions. The data collected during the November 2010 Pb–Pb run at √s

NN = 2.76 TeV were analyzed and multiple measurements of the properties of the hot and dense matter were obtained. Global event properties, detailed study of jet production and jet properties, isolated photons, quarkonia and weak bosons were measured and compared to pp data and Monte Carlo simulations.


22 H i g h l i g h t s 2 0 1 1

Charged particle multiplicity density dNch/dη per participant pair for different centralities as a function of η.

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Missed Quark Matter 2011? Proceedings now online

Read the research from this year’s conference, including the first results from the LHC.

iopscience.org/jphysg/quarkmatter2011

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a planar arrangement P McEwan and M Freer 2004 Journal of Physics G: Nuclear and Particle Physics 30 447–463.

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Nuclear and Particle Physics - cms.iopscience.iop.orgcms.iopscience.iop.org/alfresco/d/d/workspace/SpacesStore/7826e53b... · journal of Physics G: Nuclear and Particle Physics Highlights