Nuclear  -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, p T - cut  - radiation of discrete nuclear levels Two-stage process of nuclear excitation Nuclear beam monitoring at LHC Conclusions ``

 *  *-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, ; J.Phys.G24,1998 C.Bertulani, nucl-th/ , 2001

Peripheral Heavy Ion Collisions (b > R A1 + R A2 ) Advantages: Large photon=photon energy in center mass system  s (  ) < 300 GeV at LHC Large electromagnetic cross- section of particle production  EM ~ Z 4  EM (PbPb)  200Kbarn  EM (CaCa)  3Kbarn Small background from the strong AA interactions Program: Resonance production in  *  * -fusion a)Quark content, Г  *  * ~ Q 4, Q - quark charge, Gluebal is forbidden to first order b) Meson size, on threshold  *  r M 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/ Au +Au      X, Au +Au    ,      X 2 tracks p T < 100 Mev Charge sum = 0  signal Charge sum  0  background One or more neutrons in ZDC 00 e+e 

Equivalent Photon Spectra Fig.1. Geometry of two photon interaction. Beam direction is perpendicular to the picture plane. b 1 and b 2 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 q T dependence of equivalent photon spectrum for  = 10 GeV. Solid line is for Gauissian form factor, dott line for point charge. Vertical line is for q T =1/R G. 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> R 1 + R 2 ) ``  *  * -fusion  * A - photonuclear desintegration AA - strong interactions in grazing collisions Bertulani, Baur, 1985, 1988 Kraus, Grener, Soft, 1997 Baur, Hencken, 1997, 1998, 1999 Klein, 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 `` 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) mbarn(incl), 36 mbarn(excl)

Possible Signature of Peripheral AA collisions at LHC Our suggestion is to 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 E t Register the intact nuclei after interaction A+A  A+A+M Use the small p t of produced particles `` But (AA A*A) 0.1 mbarn  

Kinematics of the Secondary  -radiation Dependence between the energy E  and the polar    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  rad <   ' < 150  rad Energy of  '–radiation will be corresponded to the region 21 GeV < E  '  < 26 GeV ``

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 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 ``

Two-step mechanism of nuclear excitation V.Korotkikh, K.Chikin Preprint INPH MSU /641 nucl-th/ , in press 1. QED + Weizsacker-Williams 2. Ca + Ca a) L = (2  4)10 30 cm -2 sec -1 b) Well famous form factors of discrete levels 3. e + Ca  e' + Ca  ( P, E 0  ' ) 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 ``

Main Formulae for Two Stage model `` 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 40 Ca. Angular distribution of secondary photons for sum over all discrete levels E  ' = 0÷26 GeV (main contribution) Uniform distribution   '  rad    ``

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. ``

`` 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 ``

Photon Registration Rate and Accuracy of Luminosity Monitoring Ca + Ca  Ca + Ca * (3  ) + e + e     '  + Ca  int = 5 barn L = (2  4)10 30 cm -2 sec -1   '  =  rad   '  TOTEM LHC E  ' = 25 GeV 4 radiation length  Geom  0.35  L  =  dN  /dt = 10 6 photon/sec  t = 10 msec ``

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 + 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 ``