View
215
Download
0
Tags:
Embed Size (px)
Citation preview
Lepton Pair Production Accompanied by Giant Dipole Resonance at RHIC and LHC
M. C. Güçlü and M. Y. Şengül
İstanbul Technical University
WW2011 Winter Park - Colorado 1
Işık University 31/03/ 2006 2
Particle production from EM Fields
* Lepton-pair production
* Beam Lifetime (electron capture and nuclear dissociation)
* Detector background
* Impact parameter dependence
* Test of QED at high fields
WW2011 Winter Park - Colorado 3
21 RRb
1Z
2Z
Collisions of Heavy Ions
WW2011 Winter Park - Colorado 4
Particle production from EM FieldsLarge number of free lepton-pair production
WW2011 Winter Park - Colorado 5
Particle production from EM Fields
Bound-free electron – positron pair production)
WW2011 Winter Park - Colorado 6
Nuclear dissociation (Giant Dipole Resonance)
Particle production from EM Fields
WW2011 Winter Park - Colorado 7
Collision Parameters :
22:
mcsfrequencieCritical crit
b
ctfreqFourierMaximum
1max:.
ce
)mc(E:FieldECritical critic
22
2b
ZeE:FieldEMaximum imummax
WW2011 Winter Park - Colorado 8
Electromagnetic four vector potential
AAF Electromagnetic field tensor
μμν
μν AFF
LLLL
ΨγΨe)Ψmˆ(iΨ μ41
e
InteractMaxwellelectronQED
)2()1( AAA
]2.exp[
)()(
8)1( 22220220 b
qiqqq
qqZA
yxz
z
)1()1( 0AAz
0)2()1(
0)2()1(
yy
xx
AA
AA
QED Lagrangian :
WW2011 Winter Park - Colorado 9
Lepton-Pair Production
Semi Classical Action :
)(:|)()(|:)(4
txxtxdS int0 LLFree Lagrangian :
)()()()( xmixx 0L
Interaction Lagrangian :
)()()()( xAxxxL
int
WW2011 Winter Park - Colorado 10
Total Cross Section for Free Pair Production
):():():():,(
):():():():,(
12)(
21)(
pTqpFpkFpqkA
pTqpFpkFpqkA
kq
kq
3 3 22( ) ( )
8
1, : , :
4 2p k q p
q k
d kd qd pA k q A k q
WW2011 Winter Park - Colorado 11
)()(4
):( 222222
22
qfqGq
ZqF ZE
)()()()(
1)()()(
)1()1(
22):(
qppk
p
uuuu
qkEEEpT
zs
z
s
zzqkspkq
Scalar part of EM Fields in momentum space of moving heavy ions;
Amplitude Tkq relates the intermediate-photonlines to the outgoing-fermion lines
Free electron-positron pair production
WW2011 Winter Park - Colorado 12
SPS , γ=10, Au + Au , σ=140 barn
RHIC, γ=100, Au + Au , σ=36 kbarn
LHC, γ=3400, Pb + Pb , σ=227 kbarn
)(ln322 PTfreefree ZZ
Electron Capture Process
WW2011 Winter Park - Colorado 13
eZeZZZ bsaba ,...2/11)(
Positron Wave-Function
')(
q
r.qi)(q ueN
WW2011 Winter Park - Colorado 14
)1(2/
iaeN a
v
Zea
2
1e
a2N
a2
2
' is the distortion (correction term)due to the large charge of the ion.
Distorted wave-functionfor the captured-electron
WW2011 Winter Park - Colorado 15
)(.2
1)( rum
irnon
HaZr
Hrnon e
a
Z /
2/31
Using the positron and the captured electron wave-functions, direct term of the Feynman diagram can be written as:
WW2011 Winter Park - Colorado 16
.)(
)1()1();(
);()(.2
12
)(
)()()(
)('
').('3)(.3
)()(
sp
Zss
Z
qb
p s
rqpia
rpirnon
qab
E
uuuuErA
eNrdErAerm
ird
di
S
qPP
2
0q
)(qba
)()(qab
)(2
2
0q
)(q
)(2
SSbd
Sbd
Having the amplitudes for the direct and crossed diagram, the cross section for BFPP is;
WW2011 Winter Park - Colorado 17
WW2011 Winter Park - Colorado 18
Total Cross Section for Bound-Free Pair Production
BABFPP )ln(
23222 /BFPPBFPP )ba(
a)b(P
Impact parameter dependence probability for Bound-Free Pair Production
Bound- free electron-positron pair production
WW2011 Winter Park - Colorado 19
RHIC, γ=100, Au + Au , σ=83 barn
LHC, γ=3400, Au + Au , σ=161 barn Pb + Pb, σ=206 barn
)/ln(52 PTfreebound ZZ
FIG. 2: BFPP cross sections for two different systems as functions of thenuclear charge Z [8].
WW2011 Winter Park - Colorado 20
FIG. 3: BFPP cross sections for two different systems (Au+Au-dashed line andPb+Pb-solid line) as functions of the [8].
WW2011 Winter Park - Colorado 21
FIG. 4: The differential cross section as function of the transverse momentum of the produced positrons [8].
WW2011 Winter Park - Colorado 22
FIG. 5: The differential cross section as function of the longitudinal momentum of the produced positrons [8].
WW2011 Winter Park - Colorado 23
FIG. 6: The differential cross section as function of the energy of the produced positrons [8] .
WW2011 Winter Park - Colorado 24
FIG. 7: The differential cross section is shown as function of the rapidity [8].
WW2011 Winter Park - Colorado 25
WW2011 Winter Park - Colorado 26
What about experiments at
SOLENOIDAL TRACKER ( STAR ) ?
RHIC: Relativistic Heavy Ion Collider
Energy =100 GeV/nucleon
Au + Au collisions
WW2011 Winter Park - Colorado 27
)()()(2 bPbPbPbd hadronicnoXnXnee
Cross Section of electron-positron pairs
accompanied by nuclear dissociation
Giant Dipole Resonance
eeAuAuAuAu
The total cross section of electron-positron pair production with giant dipole resonance
)()( 22 bPbbPd GDRee
GDR
ee
2)(
b
SbPGDR
WW2011 Winter Park - Colorado 28
the probability of electron-positronpair production
the probability of a simultaneousnuclear excitation as a function ofimpact parameter[9].
2/322 )(2
1)(
ba
abP
eeee
WW2011 Winter Park - Colorado 29
z
z
PP
PPY
0
0ln2
1
2/12220 )( PzPPM
2/122 )( yx PP P
Rapidity:
Invariant mass:
Transverse momentum :
15.1Y
MeVMMeV ee 265140
MeVP 65
Kinematic restrictions at STAR experiment
Adams J. At al. Phys. Rev. A 63:031902 (2004)
WW2011 Winter Park - Colorado 30
Results:
mbbPbPbPbd hadronicnoXnXnee 52.1)()()(2
eeAuAuAuAu
bbPbd ee 32.0)(2
)()(3.0)(2.06.1exp mbsyststat
Şengül, M. Y., Güçlü, M. C., and Fritzsche, S., 2009, Phys. Rev. A 80, 042711
BOUND-FREE ELECTRON-POSITRON PAIR PRODUCTION with GIANT DIPOLE RESONANCE
34
the probability of electron-positronpair production
the probability of a simultaneousnuclear excitation as a function ofimpact parameter
2/322 )(2)(
ba
abP BFPPBFPP
21
b
S)b(P
C
)()(2 )1(
min
bPbPbdb XnnC
b
BFPPGDRBFPP
INTEGRATED CROSS SECTIONS FOR GOLD-GOLD COLLISIONS AT RHIC ENERGIES AND FOR LEAD-LEAD
COLLISIONS AT LHC ENERGIES FOR FREE AND BOUND-FREE PAIR PRODUCTION
Untagged Tagged TaggedAu+Au at RHIC-FREE
34000 1630 1980
Pb+Pb at LHC-FREE
212000 10200 12400
Au+Au at RHIC-BFPP
94.5 4.5 5.5
Pb+Pb at LHC-BFPP
202 9.7 11.7
32
)b( )mb(nn11 )mb(XnXn
WW2011 Winter Park - Colorado 33
FIG. 8: The probability of positron pair production with (a) gold beams at RHIC and (b) lead beams at the LHC as a function of b with XnXn (dashed line) and 1n1n (dotted line) andwithout nuclear excitation [11].
Şengul, M. Y., and Güçlü, M. C., 2011, Phys. Rev. C ,83,014902.
FIG. 9: The differential cross section as function of energy of theproduced positrons is shown in the graph (a) for RHIC and (b) for LHC.And the differential cross section is shown as function of the longitudinalmomentum of the produced positrons in the graph (a) for RHIC and (b) for LHC [11].
WW2011 Winter Park - Colorado 34
FIG. 10: The differential cross section as function of transversemomentum of the produced positrons is shown in the graph (a) for RHICand (b) for LHC. And the differential cross section is shown as functionof the rapidity of the produced positrons in the graph (a) for RHIC and (b) for LHC [11].
WW2011 Winter Park - Colorado 35
WW2011 Winter Park - Colorado 36
CONCLUSIONS:
1. We have obtained impact parameter dependence of free-free and bound-free electron-positron pair production cross section by using the semi-classical two photon method.
2. Our calculations agree well with the other calculations shown at references.
3. We have also obtained cross sections as a function of rapidity, transverse momentum and longitudinal momentum of produced positrons and compered with the STAR experiment.
4. We can repeat the similar calculation for the FAIR energies.
5. Can we use this method to calculate the production of other particles such as mesons, heavy leptons, may be Higgs particles ?
REFERENCES:1) C.A. Bertulani and G. Baur, Phys. Rep. 163, 299 (1988).
2) M.J. Rhoades-Brown, C. Bottcher and M.R. Strayer, Phys. Rev. A 40, 2831 (1989).
3) A.J. Baltz, M.J. Rhoades-Brown and J. Weneser, Phys. Rev. A 50, 4842 (1994).
4) C.A. Bertulani and D. Dolci, Nucl. Phys. A 683, 635(2001).
5) V.B.Berestetskii, E.M. Lifshitz and L.P. Pitaevskii, Relativistic Quantum Field Theory (Pergamon Press, NewYork, 1979).
6) J. Eichler and W.E. Meyerhof, Relativistic Atomic Collisions (Academic Press, California, 1995).
7) H. Meier, Z. Halabuka, K. Hencken, D. Trautmann and G. Baur, Phys. Rev. A 63, 032713 (2001).
8) Şengül, M. Y., Güçlü, M. C., and Fritzsche, S., 2009, Phys. Rev. A 80, 042711.
9) K. Hencken, G. Baur, D. Trautmann, Phys. Rev. C 69, 054902 (2004).
10) M.C. Güçlü, M.Y. Şengül, Progress in Part. and Nucl. Phys. 59, 383 (2007).
11) Şengul, M. Y., and Güçlü, M. C., 2011, Phys. Rev. C ,83,014902.
WW2011 Winter Park - Colorado 37