Nuclear g -Radiation in Peripheral HIC at LHC

Nuclear -Radiation in Peripheral HIC at LHC

V.L.Korotkikh, L.I. SarychevaMoscow State University, Scobeltsyn Institute of Nuclear Physics

CMS meeting, December 2001

•Two photon physics in AA collisions•Comparison * * , *A and AA in the

peripheral processes, pT - cut• - radiation of discrete nuclear levels•Two-stage process of nuclear excitation•Nuclear beam monitoring at LHC•Conclusions

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**-Luminosity for AA collisions at LHC

Effective -Luminosity for AA at LHC, LEP200 and a future NLC/PLC with photons

from laser backscattering

G.Baur, K, Hencken, CMS Note, 2000.060; J.Phys.G24,1998

C.Bertulani, nucl-th/0104059, 2001

Peripheral Heavy Ion Collisions (b > RA1 + RA2 )

Advantages:• Large photon=photon energy

in center mass system

s () < 300 GeV at LHC

• Large electromagnetic cross-section of particle production

EM ~ Z4

EM(PbPb) 200Kbarn

EM(CaCa) 3Kbarn

• Small background from the strong AA interactions

Program:• Resonance production in * * -fusiona)Quark content, Г** ~ Q4, Q - quark charge,

Gluebal is forbidden to first order

b) Meson size, on threshold * rM r

c)Expectation of Higgs meson production

at small background from strong interactions

• Exotic meson production* + * Hybrids (q, anti q, gluon)

* + Pomeron Hybrids , Glueball

Pomeron + Pomeron Hybrids , Gluebal

• Lepton pair production* + * e e (control QED, unitarity)

* + *

• Vector meson production* + * , * + * 0 + A

First experimental Result of Peripheral - Meson Production

S.Klein(STAR, RHIC, 130AGeV), nucl-ex/0108018

Au +Au X , Au +Au , X • 2 tracks• pT < 100 Mev• Charge sum = 0 signal• Charge sum 0 background • One or more neutrons in ZDC

0

e+e

Equivalent Photon Spectra

Fig.1. Geometry of two photon interaction.

Beam direction is perpendicular to the picture

plane. b1 and b2 are the

distances from the nuclear centers to the photon interaction points P.

-Luminosity for PbPb collisions at LHC

-Luminosity for PbPb with A=2950 as a function of rapidaty

y() for different values of M

qT dependence of equivalent photon spectrum for = 10 GeV. Solid line is for Gauissian form factor, dott

line for point charge. Vertical line is for qT=1/RG. Baur et al. CMS NOTE,2000/060

Production of a single meson in * * fusion

R

Resonance Cross-Sections in * * fusion at LHC

Meson cross-sections for fusion in PbPb and CaCa collisions at LHC

CaCa Resonance

G. Baur et al. CMS NOTE,2000/060

Three process of the resonance production in the peripheral AA collisions (b> R1 + R2)

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* * -fusion

* A - photonuclear desintegrationAA - strong interactions in

grazing collisions

Bertulani, Baur, 1985, 1988Kraus, Grener, Soft, 1997Baur, Hencken, 1997, 1998, 1999Klein, Nystrans, 1999

Pshenichnov, Mishustin, 1999

RELDIS

Anderson, Gustafson,Hong, FRITIOF

(PbPb) 40 mbarn

(PbPb) 200 barn(PbPb) 7 barn

rapidaty distribution for PbPb collisions at LHC

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K.A.Chikin, V,L. Korotkikh, A.P.Krykov,L.I.Sarycheva, I.A.Pshenichnov, J.P.Bondorf, I.M.Mishustin. Eur.Phys.J.A8(2000)537

106 mbarn(incl), 36 mbarn(excl)

Possible Signature of Peripheral AA collisions at LHC

Our suggestion isto register the nuclear secondary ’

radiation of HI after interaction

How to select

the peripheral collisions?

• Use the correlation of b and multiplicity n

• Use the correlation of b and transverse total energy Et

• Register the intact nuclei after interaction A+AA+A+M

• Use the small pt of produced particles

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But (AA A*A) 0.1 mbarn

Kinematics of the Secondary -radiation

Dependence between the energy Eand the polar ofphoton, emitted by the relativistic nucleus at LHC energy. Axis Z is along nuclear direction.

The lines correspond to the discrete excited levels:

Roman pots of TOTEM have

20 rad < ' < 150 radEnergy of '–radiation will be corresponded to the region

21 GeV < E' < 26 GeV

Caγ)E,(λCa 0γ

P*

MeV3.74,3 1.1

MeV3.90,2 2.1

MeV4.49,5 3.1

MeV6.29,3 4.2

MeV6.59,3 5.3

)E,(λCa 0γ

P*

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Nuclear-radiation and e+e production

Huge cross-section:

Pb Pb Pb Pb + e+e (220 Kbarn)

Ca Ca Ca Ca + e+e (1.4 Kbarn)

Baron, Baur. Phys. Rev. D46 (1992) R3695

Guclu et al. Phys. Rev. A51 (1995) 1836

Alscher et al. Phys. Rev. A55 (1997) 396

MeV3E0γ'

LHCat 3500γ *A1

GeV21E2γE 0γ'Aγ'

Properties of '-radiation

• Neutral radiation• High energy E' at LHC• Narrow collimation of 'radiation• But the direct excitation of nucleus has a small cross-section

e+e production

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Two-step mechanism of nuclear excitation V.Korotkikh, K.Chikin Preprint INPH MSU 2001-1/641

nucl-th/0103018, in press

1. QED + Weizsacker-Williams

2. Ca + Ca

a) L = (24)1030 cm-2 sec-1

b) Well famous form factors

of discrete levels

3. e + Ca e' + Ca(P, E0')

Gulkarov. Fis. Elem. Chast. at Nucl 19 (1998) 345

Discrete levels of Ca Endt et al. NPA633 (1998)

Ca + Ca Ca + Ca*(P) + e+ e int = 5.1 barn ' + Ca

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Main Formulae for Two Stage model

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Energy spectrum of

Angular distribution

Cross-section of two stage

Cross-section convolution of two process

Energy and Angular Distributions of '-rays

LHC, Ca + Ca Ca + Ca*(3) + e+ e

' + Ca

Energy distribution of secondary photons. Numbers 1, 2, …, 5 correspond to discrete levels of 40Ca.

Angular distribution of secondary photons for sum over all discrete levels

E' = 0÷26 GeV (main contribution) Uniform distribution

'rad

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Comparison of '-rays Distributions for Various Processes

1. Ca + Ca Ca + Ca*(3) + e+ e

2. Ca + Ca Ca + Ca*(3)

3. Ca + Ca Ca + Ca +

Energy distribution of secondary photons. Numbers 1, 2, 3 correspond to three processes.

Angular distribution of secondary photons for three processes.

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pp and Pure electromagnetic processes

EM(CaCa ) 3.0 barn

Possibility of Nuclear Beam Monitoring at LHC by -radiation of Nuclei Recoil

Large problem at LHC

is a monitoring

of nuclear beam luminosity

What is necessary to solve

the problem:

• Choice of a process for AA interaction

• Large cross-section of the process

• Effective detectors for registration of the process

• High accuracy of luminosity

measurement

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Photon Registration Rate and Accuracy of Luminosity Monitoring

Ca + Ca Ca + Ca*(3) + e+e

'+ Ca

int = 5 barn

L = (24)1030 cm-2 sec-1

'=rad

'

TOTEM LHC

E' = 25 GeV4 radiation length

Geom 0.35

sec/photon)107(3.5εσLdt

dN 6Geomint

γ

Δt/dtdN1

NN

δδγγ

γNL γ

2Lδ/dtdN

1Δtγ

L=dN/dt = 106 photon/sect = 10 msec

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Conclusions

• Peripheral AA interactions are studied both theoretically and experimentally

• There are some good ways to select such kind of processes

• Two stage process A +A A* + A + ee , A* * + A

has a large cross-section ( for CaCa ~ 5 barn)

• Nuclear * - radiation can be used for

a)the signature of peripheral processesb)nuclear beam monitoring at LHC

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