electromagnetic form factors of the proton in the time-like region with the panda detector
DESCRIPTION
Electromagnetic form factors of the proton in the time-like region with the PANDA detector. GDR/LQCD Autrans, 6-7 Juin 2005 Saro Ong IPN Orsay and UPJV Amiens. http//www.gsi.de/panda. PANDA detector. Layout of the detector (top view). Main Topics. - PowerPoint PPT PresentationTRANSCRIPT
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Electromagnetic form factors of the proton in the time-like region with the PANDA detector
GDR/LQCD Autrans, 6-7 Juin 2005
Saro OngIPN Orsay and UPJV Amiens
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http//www.gsi.de/panda
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PANDA detector
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Layout of the detector (top view)
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Main Topics
Charmonium (narrow charmonium and charmonium above open charm threshold)
Hybrid Charmonium and Gluballs Exotics (tetra and pentaquark up to 2.7 GeV/c2) Charm in Nuclei (charmonium absorption and mass shift
of charmed mesons in Nuclei) Hypernuclei
Open charm physics Crossed-channel Compton scattering Transverse quark distribution and Drell-Yan processes Electromagnetic FF of the proton in the time-like region
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S.K. Choi et al., Phys. Rev. Lett. 94, 182002 (2005) and hep-ex/0408126
Observation of a hybrid meson at the KEK Laboratory (Belle Collaboration).
The new meson is known as the Y(3940). It may be a hybrid meson containing a charm quark, a
charm antiquark and a gluon . It decays into omega and J/psi
LQCD predicts the presence of about 15 glueballs in the mass range accessible to the HESR (< 4.5 GeV/C2)
See for details : C. Morningstar and M. Peardon, Phys. Rev. D60, 034509 (1999)
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Panda Collaboration (350 physicists, 47 lnstitutions of 15 Countries ).We (IPNO group) propose to measure the electromagnetic FF of the proton in the time-like region.
65
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/.155.1
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_
pp
cGeVp
scmL
p
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Physics Motivation
Electromagnetic form factors of hadrons in the space-like and time-like regions provide fundamental informations on their structure and internal dynamics.
Till now, the available data in the time-like-region are limited by low statistics. The |Ge| and |Gm| separation could not be done without assumptions.
The numerical values of |Gm| in the region explored by Fermilab (E760, E835) are approximately twice as large as those in the corresponding space-like region.
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The space-like FF are reals, The time-like form factors have a phase structure reflecting the final or initial state interaction of the hadrons.
The JLab results show us that the Pauli/Dirac ratio is not observed to fall with the nominal expected power and make critical to carefully measure and separate the time-like Gm and Ge form factors
With polarized proton-antiproton reactions, the measurement of the proton FF in the time-like region should strongly discriminate between the different models suggested to fit the proton FF in the space-like region.
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M. Ambrogiani et al., Phys. Rev
D60,032002(1999)
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O. Gayou et al.,Phys. Rev. Lett. 88, 092301 (2002).E. Tomasi-Gustaffson, Proc. of the “Baryons 04” Palaiseau, France.
Jlab E01-109 approved 07/2001-07/2004
scheduled 2006 Spokepersons: Ch. Perdrisat, V. Punjabi, M. Jones, E. Brash 20 Laboratories, 80 people
0
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Cross section ( )A. Zichichi, SM. Berman, N. Cabibbo, R. Gatto, Nuovo Cimento 24, 170 (1962)
]sin4
)cos1([2)(cos
222
222
EM G
s
mG
sd
d
eepp
S
m241
cm
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6.0cos
10.2 239int
cmL
S (GeV2) σ (pb) N(events)
8.84 10.8 21600
10.78 2.82 5643
14.36 0.8 1617
30. 0.021 42
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Events selection
The analysis of the data is based on the identification of the coplanar e+e- pairs tracks collinear in the CMS with an invariant mass compatible with the center of mass energy of the p barp system.
Simulations of the signal and backgrounds are in progress.
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B. Ramstein and J. Van de Wiele (private communication)
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MP. Rekalo and E. Tomasi-Gustafsson, EPJ A22, 331 (2004) 1-2 interference in the annihilation channel ?
eepp
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Backgrounds processes
1) Photon conversions and Dalitz decays
2) Hadronic two body decays
3) J/ψ (γ) or Inclusive J/Ψ production
pp
pp
pp0
00
pp
XJpp
eeJpp
/
/
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Energy deposit in ECAL @ 0.5GeV Th. Zerguerras (private communication)
e-
90% e- incident energy measured
Need for another independant identification (TPC, Kinematics, DIRC, Scint. …)
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Kinematical separation of and e+ e-
at 5 GeV p_bar p (T. Hennino, private communication)
P(-)–P(e-) = 10 MeV/c ! independant of angle and incident energy
[0o,20o]
Resolution in momentum (MeV/c) for 9 angular intervals
[160o,180o][140o,160o][120o,140o]
[100o,120o][80o,100o][60o,80o]
[40o,60o][20o,40o]
170 70
17
34
7.5
6.56.5
10
13
Below 90 degrees, identification by ECAL is sufficient
CONCLUSION:
Might be of help in the backward region
Other criteria for a better separation have to be worked out (TPC, DIRC, Scint. )
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(PANDA Collaboration)FAIR-ESAC/Pbar/Technical Progress Report, January 2005. TPC Option for tracking particles
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Antiproton-proton scattering with polarizationPAX Collaboration (www.fz-juelich.de/ikp/pax)
Ay the transverse single spin asymmetry (SSA) in annihilation (beam or target polarized):
eepp
/]/sin)cos1[(
4/
Im2sin
2222
22
*
EM
MEyy
GGD
mQ
D
GGPA
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Py is the normal polarization to the scattering plane of the outgoing hadron in annihilation e+e- to p barp
The polarization Py does not require polarization in the initial state.
The measurement of the SSA would strongly discriminate between the models suggested to fit the proton Ge/Gm data in the space like region
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A. Z. Dubnickova, S. Dubnicka, M. P. Rekalo, Nuovo Cim. A109, 241 (1996).S.J. Brodsky et al., Phys. Rev. D69, 054022 (2004) and References therein
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Conclusion
Separation of |Ge| and |Gm| in the time-like region with the detector PANDA up to
S > 15 GeV2. With a transversely polarized proton
target, we would determine the relative phase between Ge and Gm by measuring the transverse single spin asymmetry.