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Measurement of the Hard photodisintegration of a proton-pair in the 3 He nucleus. Running now in JLab, hall A E03-101:GamPP n p p Ishay Pomerantz, Tel-Aviv.

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Presentation on theme: "Measurement of the Hard photodisintegration of a proton-pair in the 3 He nucleus. Running now in JLab, hall A E03-101:GamPP n p p Ishay Pomerantz, Tel-Aviv."— Presentation transcript:

1 Measurement of the Hard photodisintegration of a proton-pair in the 3 He nucleus. Running now in JLab, hall A E03-101:GamPP n p p Ishay Pomerantz, Tel-Aviv University

2 Hall A Collaboration Meeting E03-101:GamPP Hard photodisintegration: A process in which a high energy photon is absorbed by a nucleon pair, resulting in two nucleons with large transverse momenta. n p p 1-5 GeV 3 He GeV/c Spectator neutron GeV/c γ n p p

3 Hall A Collaboration Meeting E03-101:GamPP Motivation: Significant time has been devoted by JLab to investigate the hard photodisintegration of the Deuteron. The breakup of a pp pair is a direct continuation of this study. Deuteron results indicates that the quarks are the relevant degrees of freedom in describing these interactions, yet pQCD fails to describe them. Several quark models have been formulated, and their validity requires testing. n p p

4 Hall A Collaboration Meeting E03-101:GamPP Two possible mechanisms can explain the high P t: Breaking a transverse compact object (Initial state) Hard rescattering (Final state) n p p

5 Hall A Collaboration Meeting E03-101:GamPP Breaking a transverse compact object: The high P t Results from initial state correlation. A very minute part of the pair wave function. n p p p p γ QGS Quark Gluon String Model V. Yu Grishina et al. EUR.J.Phys.A10,355(2000) p γ p RNA Reduced Nuclear Amplitudes S.J. Brodsky, J.R. Hiller,Phys. Rev. C 28 (1983) 475

6 Hall A Collaboration Meeting E03-101:GamPP Hard rescattering: One proton absorbs the photon, and then interacts with the other member of the pair. Also a rare case (large c.m. scattering angle). n p p HRM γ ψ pp p p Hard Rescattering Model L.L. Frankfurt, G.A Miller,M.M. Sargasian, M.I Strikman, Phys. Rev. Lett.84,3045(2000)

7 Hall A Collaboration Meeting E03-101:GamPP Experimental setup n p p Electrons 3 He Radiator Target HRS Photons Protons

8 Hall A Collaboration Meeting E03-101:GamPP The radiator n p p

9 Hall A Collaboration Meeting E03-101:GamPP Planned measurements: Scaling of the cross section with s Oscillations The light cone momentum distribution of the spectator neutron Polarization transfer n p p

10 Hall A Collaboration Meeting E03-101:GamPP Scaling of the cross section with s: constituent counting rule predicts: For the case of: N =1( ɣ ) +6(pp)+3(p)+3(p)-2=11 n p p

11 Hall A Collaboration Meeting E03-101:GamPP Oscillations: A unique feature of hard rescattering n p p HRM γ ψ pp p p

12 Hall A Collaboration Meeting E03-101:GamPP The light cone momentum distribution of the spectator neutron: The width of the distribution The asymmetry around α n =1 indicates the s dependence. n p p Compact object Rescattering

13 Hall A Collaboration Meeting E03-101:GamPP Polarization transfer: At the moment, doesn't seem feasible because of low rates at high energy and priority considerations. n p p Deuteron data X. Jiang et al. Phys. Rev. Lett. 98, (2007)

14 Hall A Collaboration Meeting E03-101:GamPP Offline analysis: Full kinematic reconstruction. Application of cuts. Comparison of the various reconstructed kinematic variables with a simulation. Inspection of the Events/Unit charge ratio. Extraction of the scaled cross section and α n. n p p

15 Hall A Collaboration Meeting E03-101:GamPP Full kinematic reconstruction. n p p

16 Hall A Collaboration Meeting E03-101:GamPP Full kinematic reconstruction. n p p Neutron momentumReaction pointPhoton energy Gev/c Gevm

17 Hall A Collaboration Meeting E03-101:GamPP Applying cuts on: Coincidence events. Detector acceptance. Reaction point within the target. An energy bin of 200MeV from the photon end point. n p p Gev Photon energy at beam energy 2.1GeV End Point

18 Hall A Collaboration Meeting E03-101:GamPP Comparison of the various reconstructed kinematic variables with a simulation. Simulation is used to evaluate coincidence efficiency n p p Red – Generated events(scaled)Black- events that fall within acceptance Gev/c m

19 Hall A Collaboration Meeting E03-101:GamPP Events/Unit charge as a function of the run no. n p p With radiator W/o radiator Eγ=3.1GeV

20 Hall A Collaboration Meeting E03-101:GamPP Inspection of the No. events/charge ratio. Oops – a pressure drop ! n p p IOC reboot Fixed

21 Hall A Collaboration Meeting E03-101:GamPP Extraction of the scaled cross section and α n. n p p

22 Hall A Collaboration Meeting E03-101:GamPP Very Preliminary (online) results: Points at 1.1 GeV 2.1GeV 3.1GeV 4.1GeV n p p

23 Hall A Collaboration Meeting E03-101:GamPP Very Preliminary (online) results: Possible interpretation n p p ?

24 Hall A Collaboration Meeting E03-101:GamPP Plans for next week 1.65 GeV 2.4 GeV 4.72 GeV Maybe 0.8 GeV n p p

25 Hall A Collaboration Meeting E03-101:GamPP Summary In Hard photodisintegration two protons are found to have large transverse momentum. The goal of the experiment is to find the origin of this momentum. We look at features of the cross section, and the light cone momentum distribution to establish an explanation. We found high cross section point at 2.1GeV that we'll further investigate, and we plan to continue to 4.7GeV. n p p


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