Strangeness opportunities at the LHC

Strangeness opportunities at the LHCStrangeness opportunities at the LHC

RIKEN BNL Research Center Workshop - BNL - 15/02/06

1. Strangeness at LHC energies Extrapolations / Motivations

2. Strange probes with ALICE Detector and Simulations

3. First p+p Collisions and beyondFirst measures to target

Strangeness in Collisions

Boris HIPPOLYTE, STRASBOURG

02/2006 RIKEN-BNL Research Center Workshop - BNL 2

Wroblewski factor extrapolation to LHC energies

Extrapolation at the LHCA+A ~0.45 p+p ~0.25

< >2

< >+< >λ s

ss

uu dd

Wroblewski factor:

Using thermal model description with corresponding system formalism (canonical or grand-canonical), extrapolation is straightforward.

Data compilation using Becattini et al., PR C64 (2001) 024901, hep-ph/0002267 and references therein


Excitation functions of hyperons yields in A+A

dN/dy extrapolations at the LHCfor : 10~30for : 3~6for : 0.4~0.7

Expected modificationstotal multiplicity scalingnon-equilibrium scenario


Equilibrium vs non−equilibrium scenarii in A+A

Eq. [ Oeschler et al., to be published ] [ Andronic et al., nucl-th/0511071 ]Non Eq. [ Rafelski et al., Eur. J. Phys. C45 (2006) 61 ]

Expectations at the LHC energies (eq.):

Tch ~170 MeV B ~1 MeV

Scenarii for s

Calculations fromKraus et al., (Eq.)Rafelski et al., (Non Eq.)


Blast-Wave parameters <T> and Tfo extrapolation

Global trend for Blast-Wave parameters (<T> and Tfo) is clear

Excitation functions of the radial flow velocity and the kinetic freeze-outtemperature parameters for central Au+Au or Pb+Pb collisions.

Compilation from N. Xu


Blast-Wave for Multi-Strange Baryons vs √sNN

G.E. Bruno J.Phys. G 31 (2005) s127 J. Speltz nucl-ex/0512037 S. Salur nucl-ex/0509036

Evolution of parameters up to LHC energies and systematics study for Tfo


The central detectors of the ALICE experiment

Time ProjectionChamber

-0.9< < 0.9azimuth 2length 5 mactive volume 88 m3



Inner Tracking System

-0.9< < 0.9silicon layers 6

pixel/drift/strip 2/2/2 cells(M) 9.84/23/2.6

area 0.21/1.31/4.77 m3


The central detectors of the ALICE experimentTransition-Radiation

Detector

-0.9< < 0.9azimuth 2length ~7 mactive area 736 m2



Time Of Flight

-0.9< < 0.9azimuth 2length 7.45 mactive area 141 m2



High-MomentumParticle Identification

Detector-0.6< < 0.6

azimuth 57.61°active area 10 m2



PHOtonSpectrometer

-0.12< < 0.12azimuth 100°

active area 8 m2



High-MomentumParticle Identification

Detector

PHOtonSpectrometer

Time ProjectionChamber

Inner Tracking System

Time Of Flight

Transition-Radiation Detector


Fiducial volume and reconstruction strategies

Standard / extended fiducial volume leading to high purity / efficiency for

strange particle reconstruction


Simulation of hyperons in Pb+Pb

Expected invariant mass distribution for 300 central HIJING simulated events.

R. Vernet et al. ALICE Internal Note 2005 - 042

Expected raw spectra extrapolated to 107 central events (first year Pb+Pb data).


PID Range of ALICE at mid−rapidityEstimates as in the Physics Performance Report Vol.II

for one year of Pb+Pb data-taking (central events)

107 central Pb+Pb events


Hadronization via coalescence at LHC energiesFries and Müller, EJP C34, S279 (2004)

Calculation implies assumption on transverse radial flow extrapolation

Amplitude for mixed ratio is the same at LHC than for RHIC but the limit is pushed to higher pT

Probing baryon/meson differences at LHC energies implies PID over a large pT range and ALICE is perfectly designed for this.

But first ALICE data will be elementary collisions check magnitude of this behaviour then assume

coalescence mechanisms if needed.


Simulation of hyperons in p+p

Reconstruction rates for different multiplicity regimes (soft / hard)

L. Gaudichet et al. ALICE Internal Note 2005 - 041

Expected raw spectra extrapolated to 109 events (first year p+p data).

Baryon over meson ratio in p+p collisions (gluonic baryon junction).


Mixed ratio @ UA1: p+p @ 630 GeV

Extracting mixed ratio from 1996 UA1 strange particle data

Ratio vs pT already surprisingly high in p+p data at high energies


Hard/soft/min.bias spectra @ CDF: p+p @ 1800 GeV Extrapolation using CDF strange particle publication: PR D72 (2005) 052001

Main difference between preprint and final publication is a comparison with PYTHIA 6.216

After PYTHIA tuning with pions, the bottom line is min. bias spectra is close but K0s is slightly

overestimated


Mixed ratio @ CDF: p+p @ 1800 GeV

Extracting mixed ratio from 2005 CDF strange particle data

Ratio vs pT slightly lower but compatible within errors


Mixed ratio using PYTHIA: p+p @ 14 TeV

This feature is not observed in default PYTHIA at 14 TeV:

1) Going from LO to NLO may help getting the magnitude;

2) Other ingredients may be needed to get the shape.

Simulation used for PPR analysis by L. Gaudichet

Extrapolation of the main behaviours from RHIC, UA1 and

CDF data is currently being investigated.


Conclusion

Using strangeness as a powerfull probe at LHC energies

with the PID capabilities of the ALICE experiment

a) equilibrium vs non-equilibrium scenariob) kinetic freeze-out of multi-strange particlesc) hadronization and coalescence validity at LHC

strange particles (specific probes and PID) !

First measurements of strange particles in p+p to extract:

1) interesting for baryon creation mechanisms2) references for Pb+Pb mandatory

WARNING: minimum bias trigger for p+p !

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Strangeness opportunities at the LHC