1 / 52

Inelastic J/ y differential cross sections: paper material

ZEUS week 15-17 Feb. 2012 DESY, 15/2/2012. Inelastic J/ y differential cross sections: paper material. A. Bertolin , R. Brugnera. Outline: short introduction differential p t 2 cross section in z bins differential z cross section in p t bins y (2S) to J/ y cross sections ratio

ide
Download Presentation

Inelastic J/ y differential cross sections: paper material

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. ZEUS week 15-17 Feb. 2012 DESY, 15/2/2012 Inelastic J/ydifferential cross sections: paper material A. Bertolin, R. Brugnera • Outline: • short introduction • differential pt2cross sectionin z bins • differential z cross section in pt bins • y(2S) to J/y cross sections ratio • momentum flow along the J/y direction (new) • outlook

  2. short introduction • previous ZEUS papers: • 1. Measurement of inelastic J/yphotoproduction at HERA • DESY 97-147 (July 1997) • Zeitschrift f. Physik C76 (1997) 4, 599-612 • Alessandro B. PhD thesis + Riccardo B. • 94 data • Measurements of inelastic J/y and y^prime photoproduction at HERA • DESY-02-163 (September 2002) • Europ. Phys. Journal C 27 (2003) 173-188 • Alessandro B. + Riccardo B. • 96-97 data • Measurement of Inelastic J/y Production in Deep Inelastic Scattering at HERA • DESY-05-071 (May 2005) • European Physical Journal C44 (2005) 13-25 • Alessandro B. + Alexei A. + Igor K. (+ Leonid G. + Riccardo B.) • 96-00 data • Measurement of J/y helicity distributions in inelastic photoproduction at HERA • DESY-09-077 (June 2009) • JHEP12 (2009) 007 • Alessandro B. + Riccardo B. • HERA I + HERA II

  3. paper material • as already stated several times we have to take into account several external constraints: we are in 2012, myself and Riccardo have other commitments ... • so we have to define some realistic goals for this paper: • ds / dpt2 in z slices: shown as preliminary in DIS11, all mature PHP experiments have measured it • ds / dz in ptslices: inelasticity, z, is a key variable for J/y production • provide to the theorists an inelasticity distribution at “high pt” • y(2S) to J/y cross section ratio: needed to evaluate the y(2S) ® J/y p pfeed down • study of the momentum flow (using vertex tracks) along / againstthe J/y direction of flight: theorists are telling us that this measurements is very significant, never done before in PHP

  4. MC samples produced runlib v2008a.2 last version available • 96/97 pos. data (20718 27889) • mbtake & GLOMU effic.: ok • num97v5.2 HERWIG MC • evtake + mbtakelumi: 38.0pb-1 • 98/99 ele. data (30758 32906 ) • mbtake & GLOMU effic.: ok • num98v5.0 HERWIG MC • evtake + mbtakelumi: 15.9 pb-1 • 99/00 pos. data (33125 37715 ) • mbtake & GLOMU effic.: ok • num98v5.0 HERWIG MC • evtake + mbtakelumi: 60.2 pb-1 • 03/04 pos. data (45783 51245) • mbtake & GLOMU effic.: ok • num03t6.0 HERWIG MC • evtake + mbtakelumi: 36.9 pb-1 • 04/05 ele. data (52258 57123 ) • mbtake & GLOMU effic.: ok • num05t3.0 HERWIG MC evtake + mbtakelumi: 126.5 pb-1 • 06 ele. data (58207 59947) • mbtake & GLOMU effic.: ok • num06t4.0 HERWIG MC available • evtake + mbtakelumi: 53.3 pb-1 • 06/07 pos. data before L/MERs(60005 62639) • mbtake & GLOMU effic: ok • num07t4.1 HERWIG MC available • evtake + mbtakelumi: 137.5 pb-1 w.r.t. v2007a.2 used previously some changes occurs for HERA II but the overall sum stays 354.2 pb-1 S (HERA I) = 114.1 pb-1 S(HERA II) = 354.2 pb-1 S(all HERA) = 468.3 pb-1

  5. MC samples produced HERWIG MC J/y (direct photon) HERWIG MC y(2S) (direct photon) PYTHIA MC J/y (resolved photon) PYTHIA MC c ® J/y g (resolved photon) EPSOFT MC J/y DIPSI MC: muon chamber efficiency in MC GRAPE MC: muon chamber efficiency in MC http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/psitapes.html http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/resolvedtapes.html http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/epstapes.html http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/effictapes.html

  6. EPSOFT MC vs data • generated parameters: • Wep / f.f. = Wgp flat • MX taken from EPSOFT MC of the form (1 / Mx) • exp (-b pt2), sample with b=0.5 and sample with b=1, mixed with the same weight • onlyreweighting: • reweighted to a liner dependence Wgp dependence (Wep/ 60) • to compare EPSOFT MC and data: • 60 < W < 240 GeV (as for the nominal analysis) • 0.9 < z < 1 (0.1 < z < 0.9 for the nominal analysis) • pt > 0 GeV (pt > 1 GeV for the nominal analysis) • 2 (vertex) tracks (³3 (vertex) tracks for the nominal analysis) • E(FCAL) > 1 GeV (as for the nominal analysis) • HERA I + HERA II data proton diffractive dissociation is dominant

  7. EPSOFT MC vs data S/B huge data to MC ratio for W consistent with being flat (A1 consistent with 0) in the diffractive modeling part of the sys. errors will take care of this little mismatch in pt pt2

  8. EPSOFT MC vs data decay track reaching the m chambers in the diffractive modeling part of the sys. errors will vary the (1 / MX) dependence and hence the Efcal EPSOFT MC shape

  9. HERWIG MC • based on our past experience the only observable which needs attention is the pt – pt2 distribution • effect on the acceptances is mild, NOT a touchy issue • reweight the HERWIG MC to bring the simulation closer to the data • selected phase space for the reweighing procedure: • 60 < W < 240 GeV (as in the nominal analysis) • 0.3 < z < 0.9 (avoid 0.1 < z < 0.3 where the signal is small and the non resonant background is large) • pt > 1 GeV (as for the nominal analysis) • ³ 5 (vertex) tracks (³ 3 in the nominal analysis) • E(FACL) > 1 GeV (as for the signal) • HERA I + HERA II data proton diffractive dissociation is negligible

  10. HERWIG MC pt2 reweighting procedure: fit the reconstructed dN/dpt2 in both data and MC with a suitable function, F(pt2), weight: ratio of the data to MC function, Fdata (pt2)/FMC (pt2) F is arbitrary as long as it describes data and MC 04 ele. / 05 data F = A0 +SAm cos(mw pt2) + SBm cos(mw pt2) may be this is not the best possible choice ... F = P1*(exp(P2*pt2)+P3*exp(P4*pt2)) P2: first slope P4: second slope P3: relative weight

  11. HERWIG MC 96 / 97 98 / 99 99 / 00 03 / 04 04 / 05 06 06 / 07 96 / 97 98 / 99 99 / 00 03 / 04 04 / 05 06 06 / 07 parameters are remarkably stable vs time

  12. Proton diffractive dissociation subtraction EPSOFT MC generated z diffractive events are generated at z » 1 we measure the cross section for z < 0.9 the overlap should be ZERO HOWEVER due to the finite z resolution some of the diffractive events are RECONSTRUCTED with z < 0.9 • fit the reconstructed z distribution to estimate the amount of diffractive events left after the z < 0.9 cut • for the fit the only change with respect to the nominal analysis is done for the z range: • from 0.1 < z < 0.9 • to 0.3 < z < 1 • we: • remove 0.1 < z < 0.3 because there is no diffractive yield at low z, instead observe larger non resonant background and expect contributions also from beauty and may be resolved • we add 0.9 < z < 1 to have more diffractive background and hence more “signal” for the fit

  13. Proton diffractive dissociation subtraction data HERWIG MC events / bin EPSOFT MC shape distorted by the E(FCAL) > 1 GeV and ³ 3 (vertex) tracks requirements purpose of the fit: fractions of HERWIG MC and EPSOFT MC that best describe the data

  14. Proton diffractive dissociation subtraction MC sum data events fraction / bin HERWIG MC component from fit outcome: HERWIG MC fraction for z < 0.9 is 93.9 % data: stat. errors, MC: sys. errors, due for example to the hadronic energy resolution, with size comparable to the data stat. errors, NOT shown in the above plot in the range 0.3 < z < 0.9, this fit, the result is: 0.9397566 in the nominal analysis z range, 0.1 < z < 0.9, the result is: 0.9397768

  15. Control plots for the MC mixture • 60 < W < 240 GeV • 0.3 < z < 0.9 • pt > 1 GeV • ³ 3 (vertex) tracks • E(FACL) > 1 GeV • HERA I + HERA II data events fraction / bin EPSOFT MC HERWIG and EPSOFT MC predictions are affected by (systematic) uncertainties due, for example, to the hadronic energy reconstruction NOT shown in these plots even if not too large these uncertainties are of the size of the data stat. errors (HERA I + HERA II data) in the signal part of the sys. error the W and pt HERWIG MC spectra and the hadronic energy resolution implemented in the MC, E-Pz(rec)-E-Pz(gen), will be varied accordingly

  16. Control plots for the MC mixture EPSOFT MC the uncertainty on the muon chamber efficiency is not shown for the MC histograms, its size is similar to the data statistical error, this uncertainty will be included in the signal part of the sys. error events fraction / bin

  17. Cross section vs pt2 in z slices 0.75 < z < 0.9 0.6 < z < 0.75 60 < W < 240 GeV 1 < pt2 < 100 GeV2 Alessandro: black Riccardo: blue 0.45 < z < 0.6 0.3 < z < 0.45

  18. Cross section vs pt2 in z slices 0.1 < z < 0.3 Alessandro: black Riccardo: blue • two analyses are in very good agreement

  19. Cross section vs z in pt slices 2 < pt < 3 GeV 1 < pt < 2 GeV 60 < W < 240 GeV Alessandro: black Riccardo: blue 0.9 0.9 3 < pt < 4.5 GeV pt > 4.5 GeV • two analyses are in very good agreement 0.9 0.9

  20. 2S to 1S cross section ratio basic formulas: with some algebra: PDG2010 ≡ Please use this CITATION: K. Nakamura et al. (Particle Data Group), Journal of Physics G37, 075021 (2010) and 2011 partial update for the 2012 edition. FULL details: http://www-zeus.desy.de/~bertolin/ZEUS_ONLY/zn-03004/node41.html ZEUS Note of the HERA I paper for the HERA I paper we used PDG2002: Data Br1SMu/5.88E-2/,Br2SMu/0.70E-2/,Br2S1S/55.7E-2/ in PDG2010: Data Br1SMu/5.93E-2/,Br2SMu/0.77E-2/,Br2S1S/59.5E-2/ intoday’s presentation PDG2010 values are being used

  21. 2S to 1S cross section ratio vs z • two analyses are in very good agreement

  22. 2S to 1S cross section ratio vs pt • two analyses are in very good agreement

  23. 2S to 1S cross section ratio vs W • two analyses are in very good agreement

  24. p flow against / along the J/y direction • 60 < W < 240 GeV • pt > 1 GeV • 0.3 < z < 0.9 (0.1 < z < 0.3 removed because of the small amount of signal expected and large amount non resonant background observed) • ³ 3 (central) vertex tracks • E(FCAL) > 1 GeV J/y direction of flight in the lab. • vertex tracks • pt(min) > 150 MeV • | h | < 1.75 • do not consider the m+ and m- tracks • track and J/y same hemisphere: p projection along the J/y gives a positive contribution to Palong • track and J/y opposite hemisphere: p projection along the J/y gives a positive contribution to Pagainst as discussed with F. Maltoni (UC Louvain, Be)

  25. p flow against / along the J/y direction • goal: check if the Color Singlet Model, as implemented in the LO + PS HERWIG MC, can give a reasonable description of the energy flow along the J/y direction • the against direction is studies only “as a cross check” • reminder: • in the CSM you have only a J/y and a backward “hard” gluon (transverse momentum conservation in PHP) … so along we expect almost nothing • in the Color Octet Model you have a J/y with some nearby hadronic activity (“soft” gluons) and a backward “hard” gluon … some along activity should be visible • clearly such an analysis would profit of large J/y pt(like in CMS) but theorist told us than a qualitative results in PHP would be very valuable anyway

  26. p flow against / along the J/y direction • have to measure two distributions: Pagainst and Palong • binning of each distribution: 0. 0.25 0.5 1. 1.5 2. 2.5 3. 4. 5. GeV • have to measure vs pt(J/y) • pt(J/y) bins: 1. 1.4 1.9 2.4 3.4 4.2 10. GeV (bins used for the “inelastic J/y helicity paper”) •  expect large statistical errors (like in the helicity paper) Alessandro’s analysis: (1) fit a number of J/y events for every pt(J/y) bin (6 invariant mass fits only) (2) compute Pagainst / Palong distribution for events close to the J/y mass peak (3) compute Pagainst / Palong distribution for events in the side bands (4) knowing the background below the peak normalize properly the side bands contribution for Pagainst / Palong (5) subtract (2) and (4) to get Pagainst / Palong for J/y events only (6) build Pagainst / Palong for every pt(J/y) bin using MC: add HERWIG (94 %) and EPSOFT (6 %) MC predictions (6) compare data and MC predictions both with normalization set to 1.

  27. p flow against / along the J/y direction Riccardo’s analysis: (1) build an invariant mass distribution for every pt(J/y) bin, 1. 1.4 1.9 2.4 3.4 4.2 10. , and for every p flow bin, 0. 0.25 0.5 1. 1.5 2. 2.5 3. 4. 5. , i.e. 6 x 9 distributions for Palong and 6 x 9 distributions for Pagainst (2) fit them all to get Pagainst / Palong for J/y events only (3) build Pagainst / Palong for every pt(J/y) bin using MC: add HERWIG (94 %) and EPSOFT (6 %) MC predictions (4) compare data and MC predictions both with normalization set to 1. every method has its own advantages and disadvantages, both have been used in the past … side band subtraction method has been for the inelastic J/y helicity paper how does the two methods compare ?

  28. p flow against the J/y: data comparison Alessandro: black Riccardo: blue • two analyses are in very good agreement for the Pagainst distribution

  29. p flow along the J/y: data comparison Alessandro: black Riccardo: blue • two analyses are in very good agreement for the Palong distribution

  30. p flow along / against the J/y: MC comparison Alessandro: black Riccardo: pink • two analyses are in very good agreement along against

  31. p flow along / against the J/y: MC comparison • two analyses are in very good agreement along against

  32. p flow against the J/y crosses: HERA I + HERA II data, stat. errors only continuous line: HERWIG MC, CMS only • the HERWIG MC provides a reasonable description of the data

  33. p flow along the J/y crosses: HERA I + HERA II data, stat. errors only continuous line: HERWIG MC, LO CMS + PS • the HERWIG MC provides a reasonable description of the data moreover the agreement improves as the J/y pt increases • momentum flow around the J/y does not show large deviations from the CMS picture

  34. Cross section vs pt2 in z slices

  35. Cross section vs pt2 in z slices

  36. Cross section vs pt2 in z slices

  37. Cross section vs z in pt slices

  38. Cross section vs z in pt slices

  39. Observation on cross sections • proton diffractive dissociation background is subtracted. This is fundamental for the theorists; • y(2S) feed down is not subtracted, an inclusive reconstruction of the y(2S) decay would be needed and we do not have it. But the 2S to 1S cross section ratios vs pt W and z are measured. Theorists (should) know how to correct for this. Moreover they never asked us to perform this subtraction; • J/y from any B hadron decay are not subtracted: • the ratio between B hadron to J/y to J/y from primary vertex is much smaller at HERA than at hadron colliders (CDF, D0, CMS, ATLAS) • theorists never asked us to perform this subtraction • no PHP experiment up to now has performed this subtraction • a subtraction based on data is very hard • the only subtraction we could do would be fully based on MC … likely the theorists could account for this better than us (by adding a beauty component to the QCD predictions) • the cross section we quote, the number in nb, is corrected for this effect, as explained in the following slides • we will quantify the size of this contribution

  40. J/y from b decay: effect of the quoted number of nb • for cross section vs pt2 in z slices • for every Dpt2 bin: • disregarding any difference in the correction factors for beauty: • s = N / CH L f.f. BR Dpt2 = s0 • taking explicitly the beauty correction factor into account: • s = N – Nb / CH L f.f. BR Dpt2 + Nb / Cb L f.f. BR Dpt2 • … • = s0 [1+(Nb/N)(CH-Cb)/Cb] • outcome: • if Nb/N << 1  s = s0 • if CH=Cb s = s0

  41. J/y from b decay: effect of the quoted number of nb expected number of J/y from b decay (Pythia PHP inclusive beauty sample): continuous: 0.1 < z < 0.3 dashed: 0.3 < z < 0.45 dotted: 0.45 < z < 0.6 z > 0.6: at the event level  negligible usually < 10 events, 16 at most (low z low pt) when Nb is largest Nb/N < 16/375 < 0.045 usually Nb/N < 10/400 < 0.025 total number of beauty MC events processed: 22.207.433

  42. J/y from b decay: effect of the quoted number of nb • 0.1 < z < 0.3: • s = s0 [1+(Nb/N)(CH-Cb)/Cb] • =s0 [1+0.25×(Nb/N)] • =s0 [1+ 0.25×0.045] • < s0[1+ 1.2 %]  negligible cross section increase (stat. error is > 10 % level) 0.3 < z < 0.45: CH=Cb s = s0 whatever amount of beauty we have in data the number in nb we quote for the cross section is correct for z > 0.45 Nb/N is so small that the effect is negligible anyway

  43. J/y from b decay: effect of the quoted number of nb outcome: beauty is included in the cross section and the quoted cross section, the number of nb, takes this contribution properly into account any theorist can compute the J/y cross section, according to his preferred model, compute the J/y from beauty contribution, according to his preferred model, add the two numbers and compare with our data

  44. 2S to 1S cross section ratios LO CMS prediction: s µ Gmm / m3 1S: 3096.6 MeV, 5.93 % x 92.9 keV 2S: 3686.0 MeV, 0.77 % x 304 keV naive expectation of the LO CS model: flat ratios at 0.25(2) according to the latest PDG values most of the central values are above 0.25, mild indications that the z ratio may not be flat

  45. Conclusions and outlook • the material for the paper has been presented … we have the feeling this is the best we can do keeping in mind the different constraints we have (we are not leaving in a word with an infinite amount of money and time) • last but not least: • the computation of the systematic errors will have to be carried out • a paper draft will be prepared

  46. extra slides

  47. luminosities • tuning plots: • high z (z > 0.9): EPSOFT MC tuning • medium z (z < 0.8): HERWIG MC tuning • diffractive fit: • E(FCAL) only • >= 3 tracks • cross section vs pt2 • cross section vs z • 2S to 1S ratio • /!\ check latest .for • p flow along and against

  48. ff*BR*Lumi_tot=0.0975*0.0593*468300 • ff for 60 < W < 240 GeV and Q2max=1 GeV2 • BR = ( 5.93 ± 0.06 ) × 10−2 • Lumi_tot = 468.3 pb-1 = 468300 nb-1 • PDG read on 27/1/2012 • Please use this CITATION: K. Nakamura et al. (Particle Data Group), Journal of Physics G37, 075021 (2010) and 2011 partial update for the 2012 edition. • BR(2S) = ( 7.7 ± 0.8 ) × 10−3 • BR(2S to 1S+anything) = ( 59.5 ± 0.8 ) × 10−2

  49. default values in mmumufit.kumac

  50. list of up to date funnel versions as of 15-11-2011 Beauty MC processing • 96/97 pos. data • num97v5.3 = num97v5.2 SL5 compliant • HERWIG MC: 74P717 • beauty MC: 7KP717 (num97t5.2) • 98/99 ele. data • num98v5.1 = num98v5.0 SL5 compliant • HERWIG MC: 82E819 • beauty MC: none • 99/00 pos. data • num98v5.1 = num98v5.0 SL5 compliant • HERWIG MC: 82P020 • beauty MC: 8JP020, summary ok • 03/04 pos. data • num03t6.0 • HERWIG MC: CNZ324 (50 k), CNZ424 (50 k), CNU424 (50 k), CN4Z24 (25 k) • beauty MC: none • 04/05 ele. data • num05t3.0 • HERWIG MC: DSBF25 • beauty MC: DSNE25, summary ok • 06 ele. data • num06t4.0 • HERWIG MC: ETRE26 • beauty MC: ETRE26 • 06/07 pos. data before L/MERs • num07t4.1 • HERWIG MC: FIX627 • beauty MC: FIX627, summary ok

More Related