Nuclear g-Radiation in Peripheral HIC at LHC

1
Nuclear radiation
g
Nuclear g-Radiation in Peripheral HIC at LHC
V.L.Korotkikh, L.I. Sarycheva Moscow 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

2
gg -Luminosity for AA collisions at LHC
Effective g g -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
3
Peripheral Heavy Ion Collisions (b gt RA1 RA2 )

• Program
• Resonance production in ? ? -fusion
• a)Quark content, ??? 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

• Advantages
• Large photonphoton energy in center mass system
  
• ? s (??) lt 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

4
First experimental Result of Peripheral ?- Meson
Production
?0
ee?

• S.Klein(STAR, RHIC, 130AGeV), nucl-ex/0108018
• Au Au ??? ?? ? X , Au Au ?????, ???? ? X
• 2 tracks
• pT lt 100 Mev
• Charge sum 0 ? signal
• Charge sum ? 0 ? background
• One or more neutrons in ZDC

5
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.
6
g g-Luminosity for PbPb collisions at LHC
qT dependence of equivalent photon spectrum for w
10 GeV. Solid line is for Gauissian form
factor, dott line for point charge. Vertical line
is for qT1/R
g g -Luminosity for PbPb with ?A2950 as a
function of rapidaty y(g g) for different
values of M
G. Baur et al. CMS NOTE,2000/060
7
Production of a single meson in ? ? fusion
R
, h, h,, ..., H
? p 0
8
Resonance Cross-Sections in ? ? fusion at LHC
g g
Meson cross-sections for fusion in
PbPb and CaCa collisions at LHC
CaCa ? Resonance
G. Baur et al. CMS NOTE,2000/060
9
Nuclear radiation
g
Three process of the resonance production in the
peripheral AA collisions (bgt R1 R2)
g g -fusion
Bertulani, Baur, 1985, 1988 Kraus, Grener, Soft,
1997 Baur, Hencken, 1997, 1998, 1999 Klein,
Nystrans, 1999
s
(PbPb) 40 mbarn
?
s
(PbPb) 7 barn
?
s
(PbPb) 200 barn
?
AA - strong interactions in grazing collisions
g A - photonuclear desintegration
Pshenichnov, Mishustin, 1999 RELDIS
Anderson, Gustafson,Hong, FRITIOF
10
Nuclear radiation
g
p0 - rapidaty distribution for PbPb collisions
at LHC
106 mbarn(incl), 36 mbarn(excl)
K.A.Chikin, V,L. Korotkikh, A.P.Krykov,L.I.Saryche
va, I.A.Pshenichnov, J.P.Bondorf, I.M.Mishustin.
Eur.Phys.J.A8(2000)537
11
Possible Signature of Peripheral AA collisions
at LHC
Nuclear radiation
g

• Our suggestion is
• to register the nuclear secondary g 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
  AA?AAM
• Use the small pt of produced particles

?
But (AA AA) 0.1 mbarn
_at_
?
12
Kinematics of the Secondary g-radiation
Nuclear radiation
g

• Dependence between the energy Eg and the polar
  qg of
• photon, 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 mrad lt qg' lt 150 mrad
• Energy of g'radiation will be corresponded to
  the region
• 21 GeV lt Eg' lt 26 GeV

13
Nuclear g-radiation and ee? production
Nuclear radiation
g
ee? production
Huge cross-section Pb Pb ? Pb Pb ee? (220
Kbarn) Ca Ca ? Ca Ca ee? (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
Properties of g'-radiation Neutral radiation
High energy Eg' at LHC Narrow collimation of
g'-radiation But the direct excitation of
nucleus has a small cross-section
14
Two-step mechanism of nuclear excitation
V.Korotkikh, K.Chikin Preprint INPH MSU
2001-1/641 nucl-th/0103018, in press
Nuclear radiation
g
Discrete levels of Ca Endt et al. NPA633 (1998)

• 1. QED Weizsacker-Williams
• 2. Ca Ca
• a) L (2?4)1030 cm-2 sec-1
• b) Well famous form factors
• of discrete levels
• 3. e Ca ? e' Ca(lP, E0g')
• Gulkarov. Fis. Elem. Chast. at Nucl 19 (1998) 345

Ca Ca ? Ca Ca(lP) e e? sint
5.1 barn
?? g' Ca
15
Main Formulae for Two Stage model
Nuclear radiation
g
Energy spectrum of ? ?
Angular distribution ? ?
Cross-section of two stage
Cross-section convolution of two process
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Energy and Angular Distributions of g'-rays
Nuclear radiation
g
LHC, Ca Ca ? Ca Ca(3?) e e?
?? g' 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
Eg' 026 GeV (main contribution) Uniform
distribution
qg' ? 150 mrad eq 0.35
17
Comparison of g'-rays Distributions for Various
Processes
g
Nuclear radiation
1. Ca Ca ? Ca Ca(3?) e e? 2. Ca Ca ?
Ca Ca(3?) 3. Ca Ca ? Ca Ca p0
Energy distribution of secondary photons.
Numbers 1, 2, 3 correspond to three processes.
Angular distribution of secondary photons for
three processes.
18
Nuclear radiation
g
pp and Pure electromagnetic processes
?
EM(CaCa ) 3.0 barn
_at_
19
Possibility of Nuclear Beam Monitoring at LHC by
g-radiation of Nuclei Recoil
g
Nuclear radiation

• 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

20
Photon Registration Rate and Accuracy of
Luminosity Monitoring
g
Nuclear radiation
TOTEM LHC

• Ca Ca ? Ca Ca(3?) ee?
• ??
  g' Ca
• sint 5 barn
• L (2?4)1030 cm-2 sec-1
• qg' 20?150 mrad
• jg' ? 0??360?

dL 1, dNg/dt 106 photon/sec Dt 10 msec

Eg' 25 GeV 4 radiation length eGeom ? 0.35
21
Conclusions
g
Nuclear radiation

• 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 e?e? , A ? ?
  A has a large cross-section ( for CaCa
  5 barn)
• Nuclear ? - radiation can be used for
• a)the signature of peripheral processes
• b)nuclear beam monitoring at LHC