1 / 14

Correlations between J/ ψ and charged hadrons

Correlations between J/ ψ and charged hadrons. Chun Zhang / Jiangyong Jia. Motivation how J/ ψ is produced. Gluon Gluon fusion(GG) and Gluon Fragmentation(GF) are the main mechanisms for charm pair(ccbar) production at RHIC energy.

Download Presentation

Correlations between J/ ψ and charged hadrons

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Correlations between J/ψ and charged hadrons Chun Zhang / Jiangyong Jia

  2. Motivation how J/ψ is produced • Gluon Gluon fusion(GG) and Gluon Fragmentation(GF) are the main mechanisms for charm pair(ccbar) production at RHIC energy. • The produced ccbar needs to radiate gluons in order to get ride of color and to form a J/ψ . It can radiate one hard gluon?(Color Singlet Model) or many soft gluons(Color Octet Model). • We think we may be able to discriminate these different productions by looking the azimuth correlation between the J/ψ and the hadrons produced in the same collisions, in other words, how the momentum of high pT J/ψ is balanced.

  3. GF : pT is balanced from back to back jets c cbar GG : pT is from initial kT of gluons c cbar Imaginations CSM : pT is largely balanced by the hard gluon Hard Gluon c cbar Jpsi COM : pT is largely from initial kT Jpsi

  4. Expectations we need simulations • If GF+CSM, azimuth correlation on away side, and the peak is expected to be wide, and may not center at 180 degree. • If GF+COM, azimuth correlation on away side and one may see near side peak. • If GG+CSM, azimuth correlation on away side. • If GG+COM, no away side peak, and one may see near side peak. • All above speculations assumes all the particles correlated are from the same collisions. Proton Proton collisions are the best. But dAu and CuCu may doable.

  5. J/y (mm) – h correlation

  6. Run3 PP J/ψ

  7. Run3 PP J/ψ pT Mass widow is from 2.4 GeV/c2 to 4.0 GeV/c2

  8. Azimuth Correlation between J/ψ in muon arms and charged hadrons in central arms • Trigger particle is the J/ψ in muon arms. • Associated particles are the charged hadrons in central arms • Mass widows is from 2.4 to 4.0 GeV. • Hint of away side correlation ? • pT cut for associated particles is 100 MeV/c. • This measurement is sensitive to GF/CSM. • Opposite sign as foreground and same sign as background and correlation function is normalized to per trigger yield.

  9. J/y (ee) – h correlation

  10. Using the Jpsi candidates in mass widow 3-3.2 GeV to get a good signal/bg ratio Mass distribution for same sign and opposite sign • Combined statistics from RUN3 pp and dAu • Good run list and electron ID cut from analysis note 258

  11. Trigger particle = Jpsi + background, where background can be estimated by like-sign ee pair • Thus to get the true same event Df distribution for Jpsi, we need to subtract two correlation function, I.e subtract like-sign – h Df from Trigger – h Df distribution Same event All triggers Background triggers

  12. We need to do the similar subtraction for the mixed event pairs • The mixed event is almost flat due to the decay kinematics (<pT> is small comparing to Jpsi mass) Mixed event All triggers Background triggers

  13. Comparing the Like-sign subtracted foreground and Like-sign subtracted mixed event Df distribution • No apparent jet like correlation can be seen. • We would like to go higher pT in both trigger JPsi and associated hadrons, where the GF contribution is more dominate

  14. Summary • We are currently statistic limited. • We would like to study the correlation as function of J/ψ and hadron pT. • Run5 CuCu, there are ~10000 J/ψ. • Run5 PP, we look forward !

More Related