Hovanes Egiyan Jefferson Lab for the CLAS Collaboration Material provided by: Kawtar Hafidi Lamiaa Elfassi Raphael Dupre Aji Daniel Taisia Mineeva

6/6/2012JLab Users Group Meeting 20122

6/6/2012JLab Users Group Meeting 20123

Study of the hadronization :  Process through which partons produced in elementary reactions are turned into hadrons.  Non perturbative QCD process. The presence of cold nuclear matter affects the hadronization process. Use nuclei as space-time analyzers in nuclear SIDIS  Kinematics is more constrained  Nuclear medium is understood  Nucleons serve as femto-detectors  Low final state multiplicity compared to h+A or A+A 6/6/2012JLab Users Group Meeting production time t p t col. neut. time t cn formation time t h quark/parton prehadron hadron

Space-time evolution of hadronization  Study QCD confinement  Evaluating parton energy loss in QCD medium  Possible signatures of the LPM effect  Measuring the formation times  Understanding pre-hadron structure  Multiple scattering inside nuclei Benefits for other fields  Input for studies of A+A scattering  Hadron attenuation corrections for oscillation experiments  Constraints for Monte-Carlo generators 6/6/2012JLab Users Group Meeting 20125

6/6/2012JLab Users Group Meeting A

Studied hadron production in DIS with muon beam.  20 GeV < < 220 GeV Increased attenuation as a function of z h observed for heavier nuclei. Attenuation decreases as a function of (not shown). High transverse momentum bins have increased hadron production Attenuation is reduced at high  > 50 GeV. Partonic energy loss and hadronic attentuation type models can explain these observations. 6/6/2012JLab Users Group Meeting 2012 Ashman et al., Z.Phys. C52(1991) 7

6/6/2012JLab Users Group Meeting 2012 Airapetian et al., Nucl. Phys. B780 (2007) 8

6/6/2012JLab Users Group Meeting Airapetian et al., Phys.Lett. B684 (2010) Effect increases with Q 2 and x B Goes to 0 near z=1.  Not due to multiple scattering of prehadrons or hadrons Mostly independent of  Broadening effect increases with A.  Can’t determine the functional form.

6/6/2012JLab Users Group Meeting

Electron Beam 5 GeV (50 days) & 4 GeV (7days) Targets: 2 H&Fe, 2 H&C, 2 H&Pb Luminosity ~ 2x10 34 cm -2 s -1 6/6/2012JLab Users Group Meeting Al + MT target BEAM Hakobyan et al, NIM A592 (2008)

6/6/2012JLab Users Group Meeting Daniel et al., Phys.Lett. B706 (2011)

6/6/2012JLab Users Group Meeting Daniel et al., Phys.Lett. B706 (2011) 0.3 < z < 0.8

CLAS PRELIMINARY 6/6/2012JLab Users Group Meeting R. Dupre  0 Mineeva  - Dupre  -,  + Dupre, Hakobyan

6/6/2012JLab Users Group Meeting

6/6/2012JLab Users Group Meeting

Why study CT?  CT is predicted by QCD  CT is related to the factorization theorem for exclusive processes.  Study creation of SSC.  Study the hadronization process 6/6/2012JLab Users Group Meeting Momentum Transfer Complete Transparency Glauber

Quasi-elastic A(p,2p) [Brookhaven]  A. Leksanov et al., PRL (2001) Quasi-elastic A(e,e’p) [ SLAC and JLab]  N. C. R. Makins et al. PRL 72 (1986)  G. Garino et al. PR C45 (1992)  D. Abbott et al. PRL 80 (1998)  K. Garrow et al. PR C66 (2002) Di-jets diffractive dissociation. [Fermilab]  E. Aitala et al, PRL 86 (2001) Pion Production 4 He( γ,p  - ) [Jlab –HallA]  Dutta et al, PR C68 (2003) Pion Production A(e,e’ π + ) [Jlab-HallC]  Classie et al, PRL 99 (2007) ρ 0 lepto production. [Fermilab, HERMES]  Adams et al., PRL 74, (1995)  Airaptyan et al., Phys. Rev. Lett. 90 (2003) ρ 0 lepto production [ JLab - CLAS ]  El Fassi et al, Phys. Lett. B712 (2012) 6/6/2012JLab Users Group Meeting Q 2 (GeV 2 )HERMES  FERMILAB 

6/6/2012JLab Users Group Meeting

6/6/2012JLab Users Group Meeting After W -cut After t -cut After W- and t -cuts After W-, t - and z -cuts El Fassi et al., Phys. Lett. B712 (2012)

Background shape was determined from MC simulations Acceptance corrections on event- by-event basis Invariant mass distributions are fitted with B-W + BKG Background shape determined from MC simulations. Radiative corrections applied. 6/6/2012JLab Users Group Meeting El Fassi et al., Phys. Lett. B712 (2012)

6/6/2012JLab Users Group Meeting El Fassi et al., Phys. Lett. B712 (2012)

There is visible trend towards increasing of transparency with Q 2.  Increase of 11% (Fe) and 12% (C). The onset of CT for ρ 0 happens earlier than for  +. For both 12 C and 56 F the data point are consistent with the model versions with CT included. The FMS model slightly underestimated the observed transparency increase. 6/6/2012JLab Users Group Meeting El Fassi et al., Phys. Lett. B712 (2012)

6/6/2012JLab Users Group Meeting

Thanks! 6/6/2012JLab Users Group Meeting

6/6/2012JLab Users Group Meeting

6/6/2012JLab Users Group Meeting Asaturyan et al., Phys.Rev. C85 (2012)

Short Range Correlations (covered by Or Chen) EMC Effect Hadronization in nuclei Color transparency GPDs of nuclei Photodisintegration of light nuclei 6/6/2012JLab Users Group Meeting