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Dihadron production at JLab

Dihadron production at JLab. Sergio Anefalos Pereira (INFN - Frascati). Physics Motivation. Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD. ● measuring transverse momentum of final state hadrons in SIDIS gives

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Dihadron production at JLab

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  1. Dihadron production at JLab Sergio Anefalos Pereira (INFN - Frascati)

  2. Physics Motivation Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD ● measuring transverse momentum of final state hadrons in SIDIS gives access to the transverse momentum distributions (TMDs) of partons ● pT dependent spin asymmetries measurements give us access to different TMDs, providing information on how quarks are confined in hadrons ● azimuthal distributions of final-state particles in SIDIS, in particular, are sensitive to the orbital motion of quarks and play an important role in the study of TMD parton distribution functions of quarks in the nucleon. ● the goal of looking at dihadron SIDIS is have a full picture of the collinear structure of proton. 2

  3. What we measure at 6 GeV and 12 GeV @ Jlab with dihadrons + Higher Twist distribution functions 6 GeV  e(x) and hL(x) Leading Twist 3

  4. What we measure at 6 GeV and 12 GeV @ Jlab with dihadrons + Higher Twist distribution functions 6 GeV  e(x) and hL(x) Leading Twist 12 GeV  h1(x), e(x) and hL(x) (since we will have higher Q2 coverage ~ 10 GeV2) 3

  5. Leading Twist What we measure at 6 GeV and 12 GeV @ Jlab with dihadrons + Higher Twist distribution functions In addition to pions, at 12 GeV we'll be able to detect also kaons with/k separation in the 3-8 GeV/c range. 4

  6. Dihadron vs. single-hadron SIDIS The dihadron channel have some disadvantages (more complex kinematics, new angles, unknown but measurable DiFFs appear) but it also brings a very useful advantage: in single hadron production, the observables are convolution of TMDsin double hadron production, observables are product of TMDs 5

  7. Dihadron vs. single-hadron SIDIS The dihadron channel have some disadvantages (more complex kinematics, new angles, unknown but measurable DiFFs appear) but it also brings a very useful advantage: in single hadron production, the observables are convolution of TMDsin double hadron production, observables are product of TMDs 5

  8.  X SIDIS kinematical plane and observables the fraction of the virtual-photon energy carried by the two hadrons longitudinal momentum fraction carried by the hadron 6

  9.  X SIDIS kinematical plane and observables the fraction of the virtual-photon energy carried by the two hadrons In these analysis we select events in the CFR longitudinal momentum fraction carried by the hadron it selects the current fragmentation region (CFR) and target fragmentation region (TFR). The first comprise hadrons produced in the forward hemisphere (along the virtual photon) and the latest, in the backward hemisphere 6

  10. Dihadron angles definition k k' q the angle between the direction of P1 in the + - center-of-mass frame, and the direction of Ph in the photon-target rest frame. 7

  11. Structure functions in terms of PDF and DiFF in the limit M2≪ Q2 8

  12. Dihadron with transversely polarized target model-independent extraction in collinear approximation [arXiv:1206.1836v1] Transversity using the COMPASS data for deuteron. Transversity extracted using the HERMES data for proton (red symbols) and COMPASS data for proton (blue ones) The dashed lines correspond to Torino’s transversity [arXiv:0812.4366] JLab will provide much precise data and also extend x up to 0.6. 9

  13. Dihadron @ 6GeV 10

  14. Continuous Electron Beam • Energy 0.8-5.7 GeV • 200A, polarization 85% • Simultaneous delivery to 3Halls JLab Accelerator CEBAF CLAS 11

  15. Torus magnet 6 superconducting coils beam Electromagnetic calorimeters Lead/scintillator, 1296 photomultipliers Liquid D2 (H2)target +  start counter; e minitorus • Broad angularcoverage (8° - 140° in LAB frame) • Charged particlemomentum resolution~0.5% forward dir Drift chambers argon/CO2 gas, 35,000 cells CLAS is designed to measure exclusive reactions with multi-particle final states Time-of-flight counters plastic scintillators, 684 photomultipliers Gas Cherenkov counters e/ separation, 216 PMTs Hall B: Cebaf Large Acceptance Spectrometer 12

  16. The e1f and eg1-dvcs experiments Beam polarization ~ 75 % Liquid Hydrogen target (unpolarized) Beam energy: 5.5 GeV Luminosity: 21 fb-1 Beam polarization ~ 85% Proton polarization ~ 80% Hydrogen target (NH3) Beam energy: 5.892 GeV 4.735 GeV Luminosity: 22.7 fb-1 Hydrogen target (NH3) Beam energy: 5.967 GeV Luminosity: 50.7 fb-1 Deuterium target (ND3) Beam energy: 5.764 GeV Luminosity: 25.3 fb-1 13

  17. Channel identification • semi-inclusive channel • two topologies have been analyzed: • e p  e’ +- X • e p  e’ +0 X  e’ + X   0is identified as M() X 14

  18. + - Channel identification • semi-inclusive channel • two topologies have been analyzed: • e p  e’ +- X • e p  e’ +0 X  e’ + X   0is identified as M() X dihadron sample defined by SIDIS cuts + CFR for both hadrons 14

  19. + - Channel identification • semi-inclusive channel • two topologies have been analyzed: • e p  e’ +- X • e p  e’ +0 X  e’ + X   0is identified as M() X dihadron sample defined by SIDIS cuts + CFR for both hadrons Struck quark fragmenting in a hadron pair 14

  20. Semi-inclusive selection MM > 1.5 GeV MM > 1.5 GeV 15

  21. Monte Carlo study • ClasDIS Monte Carlo (LUND) was used as event generator; • Polarized proton and unpolarized deuteron MC were used to “simulate” NH3 target; • the full MC chain; • same cuts used on data were applied. 16

  22. Monte Carlo vs. Data + data - Monte Carlo pe p p Xb y W2 Q2 xF() xF() 17

  23. Monte Carlo vs. Data + data - Monte Carlo Z+ Z Zhh Pt+ Pt- Pthh M()Rh 18

  24. Monte Carlo generated x reconstructed asymmetries Beam-Spin Asymmetry (BSA) According to this function p0 + p1sinR + p2sin 2R we have generated events with the following input parameters: p0 = 0.0, p1 = 0.03 and p2 = 0.0 19

  25. Results Beam-Spin Asymmetry (BSA) integrated over all variables Fitting function: p0 + p1sinR + p2sin 2R preliminary 20

  26. Results Beam-Spin Asymmetry (BSA) ▲ Sin  ▲ Sin  preliminary 21

  27. Results Beam-Spin Asymmetry (BSA) ▲Sin(e1f) ▲Sin(eg1-dvcs) preliminary 22

  28. Results Target-Spin Asymmetry (TSA) integrated over all variables Fitting function: p0 + p1sinR + p2sin 2R preliminary 23

  29. Results Target-Spin Asymmetry (TSA) ▲ Sin  ▲ Sin  preliminary 24

  30. Dihadron @ 12GeV 25

  31. 12 GeV CEBAF add Hall D (and beam line) Upgrade magnets and power supplies CHL-2 6 GeV CEBAF End physics program @ 6 GeV in 2012 Beam Power: 1MW Beam Current: 90 µA Max Pass energy: 2.2 GeV Max Enery Hall A-C: 10.9 GeV Max Energy Hall D: 12 GeV May 2013 Accelerator Commissioning starts October 2013 Hall Commissioning starts 26

  32. Q2 Kinematic coverage extending to higher x means lower cross sections need high luminosity: 1035 cm-2 s-1 27

  33. Wide acceptance and high resolution important in particular for hadron pair production Designed for luminosity 1035cm-2sec-1 RICH Highly polarized 11 GeV electron beam Transverse an Longitudinal polarized H and D targets RICH detector allows kaon detection CLAS12 Configuration (Hall-B) FTOF DC R3 R2 R1 EC HTCC PCAL Solenoid Torus 28

  34. target particle’s trajectory DC3  DC1 DC2 beam pipe Layout of the RICH ONE CLAS12 SECTOR Requirements: • /k/p separation in the 3-8 GeV/c range •  rejection >500 Constraints: • the detector must fit in 1m • low material budget • large area for the photodetectors (several m2) • increasing azimuthal angle  decreasing momentum Solutions: • mirrors to focalize the light in small area • variable aerogel thickness from 2 to 6/8 cm Different pattern: • Cerenkov photons from small angle, high momentum particles directly detected • photons from large angle and lower momentum particles are reflected toward the photodetectors and pass twice through the aerogel 29

  35. SoLID Configuration (Hall-A) High 1036 luminosity 8.8 and 11 GeV polarized beam Transverse and Longitudinal Polarized 3HeTarget > 60% polarization Large acceptance with full azimuthal-angle coverage Wide acceptance and high resolution Effective pol. neutron target 30

  36. Flavor separation at JLab the asymmetry for a neutron target (for the specific case of the π+π− final state) can be written as: the equivalent equation for the proton is combining these two asymmetries (on neutron and proton targets) the uvand the dvflavors could be extracted separately. 31

  37. Flavor separation with JLab 32

  38. Dihadron production on neutron @ Jlab 11 GeV Projected statistical error for data on a neutron target. The yellow band represent the spread in predictions using different models for h1(x) (top plots) 33

  39. Dihadron production on proton @ Jlab 11 GeV 34

  40. Summary 6 Gev ●the first measurements of dihadron ALU and AUL asymmetries have been presented; ●preliminary results of a non-zero BSA and TSA for +- pair have been shown (will look at +0 as well); 12 GeV ● Jlab @ 12 GeV will measure transverse target SSA in hadron pair production in SIDIS and study the transversity distribution function and interference effects in hadronization using transverse polarized protons (CLAS12) and neutrons (SoLID); ● Flavor separation will also be possible combining both data (proton and neutron) to to extract the uvand the dvflavors separately. ●Measurements with kaons in the final state will provide important information about strange quarks. 35

  41. Backup slides 36

  42. Generated and reconstructed asymmetries p1 = 0 p2 = 0 p1 = 0.03 p2 = 0 p1 = 0 p2 = 0.03 p1 = 0.03 p2 = 0.03 37

  43. 38

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