nuclear g -radiation in peripheral hic at lhc
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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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