Semi-inclusive + and 0 asymmetries using eg1-dvcs. Sergio Anefalos Pereira (INFN - Frascati)

Transcription

1 Semi-inclusive + and 0 asymmetries using eg1-dvcs Sergio Anefalos Pereira (INFN - Frascati)

2 The eg1-dvcs experiment Ran from February to September 2009; Used the polarized electron beam at Jefferson Lab. with energy ~ 6 GeV and beam polarization ~ 85%; Used the CEBAF Large Acceptance Spectrometer (CLAS) to detect the outgoing electron and hadron; Used a solid, frozen ammonia (NH 3 ) target to get to the polarized proton with proton polarization ~ 80% and Used the Inner Calorimeter (in addiction to the EC) to detect photons at small angles. S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

3 The eg1-dvcs experiment Part A Part B Hydrogen target (NH 3 ) Beam energy: GeV GeV Luminosity: 22.7 fb -1 Hydrogen target (NH 3 ) Beam energy: GeV Luminosity: 50.7 fb -1 NH 3 ND 3 C 12 Empty Part C Deuterium target (ND 3 ) Beam energy: GeV Luminosity 25.3 fb -1 Runs with C 12 target for background evaluation S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

4 The eg1-dvcs experiment Part A Part B Hydrogen target (NH 3 ) Beam energy: GeV GeV Luminosity: 22.7 fb -1 Hydrogen target (NH 3 ) Beam energy: GeV Luminosity: 50.7 fb -1 NH 3 ND 3 C 12 Empty Part C Deuterium target (ND 3 ) Beam energy: GeV Luminosity 25.3 fb -1 Runs with C 12 target for background evaluation S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

5 Analysis procedure DIS cuts (W > 2 and Q 2 > 1) semi-inclusive channel X two topologies have been analyzed: e p e 0 X e + - X e p e + X e + X - 0 is identifyed as M( ) - 0 ( + ) is identifyed as M( + - ) (M( + 0 )) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

6 Event selection just part B was used; pre-skimmed nt22 ROOT files; target and beam corrections have been applied. Applied cuts 0.25 < etot/p < 0.4; p > 0.8 GeV ; npho > 25; cc_c2 < 0.1; ec_inner > 0.06 GeV; 18 < Q e < 41 ; 16 < Q + < 50 ; 18 < Q - < 50 ; EC fiducial cut function for electrons and photons; Zvertex cut; S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

7 + and identification p p S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

8 + and identification Db ( ) Db ( ) 0.4 < p < < p < 1.5 S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

9 sigma sigma mean mean + and identification p p p p S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

10 0 identification (IC only) DT (event start time photon time) E IC > 0.5 GeV 3 cut around the peak is applied S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

11 0 identification (IC only) Mean = Sigma = after dt cut S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

12 e p e + 0 X ( + ) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

13 + identification (IC only) all MM range all MM range MM > 1.5 GeV S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

14 + identification (IC only) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

15 + identification (IC only) X S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

16 + identification (IC only) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

17 + identification (IC only) X S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

18 + identification (IC only) W2 > 6 Z > 0.5 before after S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

19 e p e + - X ( 0 ) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

20 0 identification integrated MM > 1.5 GeV S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

21 0 identification S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

22 0 identification X S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

23 0 identification S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

24 0 identification X S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

25 0 identification S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

26 0 identification X X S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

27 0 identification S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

28 0 identification X S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

29 0 identification before Xb > 0.3 y > 0.75 Pt < 0.4 W2 > 6.5 Z > 0.32 after f 0 (980) f 2 (1270) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

30 Monte Carlo (first glance) ClasDIS Monte Carlo was used; 10,000,000 events were generated on proton; 23,000,000 events were generated on deuteron (to simulate N in NH 3 target); same cuts used on data were applied; S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

31 Monte Carlo (first glance) data MC data MC S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

32 MC contributions S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

33 MC contributions S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

34 Total fit - 0 f 0 (980) from the MC (p+d) using non 0 events f 2 (1270) + exp. data total fit background 0 (770) f 0 (980) total = background f 0 S.A. Morrow et al., Eur. Phys. J. A 39, 5 (2009) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

35 Total fit < Q 2 < < X b < 0.16 Q 2 > < X b < f 0 f 2 0 f 0 S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

36 Total fit < h < < h < 120 positive beam helicity S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

37 Total fit < h < < h < 90 negative beam helicity S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

38 Total fit exp. data total fit background + (770) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

39 Total fit - + Q 2 < < X b < < Q 2 < < X b < S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

40 Summary SIDIS cross section measurements will provide important results in a very poor scenario (specially for charged ones); present status of the analysis for both ( + and 0 ) has been shown ; we ve found kinematical cuts to select these channels; the Monte Carlo results reproduce reasonable well the data. Next steps more studies on the background subtraction; run the Monte Carlo with the polarized target and the full geometry in order to: calculate the acceptance; identification cuts. extraction of the + and 0 asymmetries. S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

41 Backup slides S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

42 Physics Motivation Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD Q 2 k k factorization: h DIS f pdf ( x) frag q, g h ( z) SIDIS cross section measurements are poorly known (especially for charged ) ; closely connected to single-pion analysis (background for the single channels); closely connected to 2-hadron analysis; however, complicated dependence of cross section on 8 kinematic variables make analysis challenging. S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

43 SIDIS cross section cross section example (just one term shown): d 8 UL sin( ) + h H +... sin 2 h R 1L 1 ( worm gear ) LT ( worm gear ) TMD-PDF (transv. polarised quarks in long. polarised proton), also called Kotzinian-Mulders function polarized FF q (p-wave component of the 2-hadron FF) S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

44 SIDIS kinematical plane and observables Cross section is a function of scale variables x,y,z z Beam polarization Target polarization U unpolarized L long.polarized T trans.polarized sin sin moment of the cross section for longitudinally polarized beam and target S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

45 SIDIS kinematical plane and observables Trento Conventions Phys.Rev. D70, (2004). Beam polarization Target polarization U unpolarized L long.polarized T trans.polarized sin sin moment of the cross section for longitudinally polarized beam and target S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

46 - S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,

47 + S. Anefalos Pereira DiFF - Pavia, Sept. 5-7,