1 / 29

Study of muon pairs production process at PANDA and its backgrounds

Study of muon pairs production process at PANDA and its backgrounds. A.N.Skachkova (JINR, Dubna). Obninsk 2010. Quark-antiquark annihilation and gluon - quark scattering subprocess in antiproton-proton collision, in which the energetic

ann-house
Download Presentation

Study of muon pairs production process at PANDA and its backgrounds

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. Study of muon pairs production process at PANDAand its backgrounds A.N.Skachkova (JINR, Dubna) Obninsk 2010

  2. Quark-antiquark annihilation and gluon - quark scattering subprocess in antiproton-proton collision, in which the energetic electromagentic particles (e, muon, photon)are produced, planned to be the subject of our study at PANDA experiment. Theresults of Monte Carlo simulation of processes with lepton pairs done by use of PYTHIA generator and PANDARoot fast simulaion tool, are presented here. They allowed to work out the cuts needed for background separation and to make reasonable estimations ofexpected selection rates for these processes. In this talk we base on the results obtained for a case of Ebeam= 14 GeV (i.e., Ecm= 5.3 GeV). Thecorrectionsfor the final estimations are planned to be donein the nearest yearson the basis of the existing detector simulation tools. Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  3. The considered processes. We present the results of study: 1. Production of lepton pairs with the continuum invariant mass. 2. “Resonance” production of lepton pair in J/Ψ decay: q q bar  ̽ c cbar  J/Ψ  l+ l- + X Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  4. Production of lepton pair(continuum Minv (l+l-) case) The process of lepton pair production q qbar ̽ / Z˚l+l- is of big physical interest because: A. The spectrumof final state leptons (e and muons) obviously depends on the form of parton distributions inside colliding protons. B.The transverse momentum of lepton pair PT (l+l-) provides the information about intrinsic transverse momentum< kT>of quark inside the proton (Fermi motion). C. The results of study of leptons angle and energy spectra distributions, based on Monte-Carlo simulation, was used for a proper “geometrical” design of such important component of PANDA detector as muon system. Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  5. V.A. Matveev, R.M. Muradian, A.N. Tavkhelidze (MMT)( V.A. Matveev, R.M. Muradian, A.N Tavkhelidze, JINR P2-4543, JINR, Dubna, 1969; SLAC-TRANS-0098, JINR R2-4543, Jun 1069; 27p. ) process, called also as “Drell-Yan process”( S.D. Drell, T.M. Yan, SLAC-PUB-0755, Jun 1970,12p.; Phys.Rev.Lett. 25(1970)316-320, 1970 ) The dominant mechanism of the l+l- production is the perturbative QED/QCD partonic 2  2 subprocess ̅qiqi ̽ / Z˚l+l- σ = 5.6 * 103 pb PYTHIA 6 simulation for the E beam = 14 GeV ( i.e., E cm =5.3 GeV) without detector effects (“ideal detector” --> all particles are detected)allows a proper account of the relativistic kinematics during the simulation Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  6. Signal l± distributions • 0 ≤ El≤ 10 GeV, <El> = 2.6 GeV, Epeak= 0.4 GeV • 0 ≤ PTl ≤ 2 GeV, <PTl> = 0.7 GeV • <Θl> = 27.3 ° some Θl > 90° !!! Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  7. Signal l± : (l = μ,e) FastSim l -- left, l +- right: • 0 ≤ Pz≤ 10 GeV, < Pz> = 4.2 GeV • -2≤ Px, Py ≤ 2 GeV Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  8. Signal l± : (l = μ,e) FastSim l -- left, l +- right: • 0 ≤ P, El, ≤ 10 GeV, < P, El> = 4.4 GeV • 0≤ PTl ≤ 2 GeV, < PTl> = 1.2 GeV PTlpeak = 1.4 GeV Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  9. Signal l± : (l = μ) FastSim l -- left, l +- right: • < Θl> = 27.2 ° some Θl >90° • 0.9 < M inv < 2 GeV Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  10. Fake muons distributions in signal events 1. The part of signal events which include fake muonsis about16%. 2. Up to 4 fake muonsin the final state. 3. Fake muonsproduction vertices are distributed within detector volume Vertex position information will be useful for Signal / Background separation Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  11. Parents of fake leptons The most probable parents of fake electrons are neutral pions (Dalits decay) muons are charged pions The most probable grandparents of fake electrons  are string (Lund model), ρ+,η, ω, Δ0 ,Δ+ ,Λ0 muons are string (Lund model), ρ0, ρ+,ω, Δ+ ,Δ++ ,Λ0 Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  12. Applied cuts for signal events • We select the events with only 2 leptons with El > 0.2 GeV, PTl > 0.2 GeV • These 2 leptons must be of the opposite sign • The vertex of origin lies within the R < 15 mm fromthe interaction point Up to now we supposed the ideal muon system and EM calorimeter covering 180o Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  13. Cuts influence on signal events Applying these cuts we have loss of the signal events: The rate of events with left fake leptonsis negligible ! Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  14. The generation was done with the use of more than 20 QCD subprocesses existed in PYTHIA (including the signal one¯q q   l +l -). The main contributions come from the following partonic subprocesses: q + g  q + g(gives 50% of events with the σ = 4.88 mb); g + g  g + g(gives 30% of events with the σ = 2.96 mb); q + q’  q + q’ (gives 18% of events with the σ = 1,75 mb); q + q bar  g + g(gives0.6%of events with theσ=5.89 E- 02 mb); q + q bar  l+ + l-(signal process gives0.00005%of bkgd events, due to σ=5.02 E- 06 mb); So, initially there is 1 signal event among 2.000.000 of QCD background i.e., initially S/B≃ 5.5 * 10-6 Background QCD processes to the q q    l +l -one The simulation was done with approximation when particles are allowed to decay within cylinder volume of R=2500 and L=8000 mm Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  15. Some examples: Low - PT scattering(gives 68% of events with theσ= 34.25mb); Single diffractive(gives 6% of events with the σ= 3.32 mb); qbar + q  l+ + l-(gives0.000012%of events,σ=5.9 E- 06mb); So, we have 1 signal event aginst 8.333.333 of Mini-bias bkgd S/B ≃ 10-7 Mini-bias background is 5 times harder than QCD background The main source of background for q qbar    l +l – are the Minimum-Bias processes: Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  16. Muon’s distributions from background events The shape of muon distributions, produced in background events do not differ from those of fake “decay” muons, produced in the signal process  a rather high probability of appearing the muon pair with the different signs of their charges in Minimum-bias events (which are other than the signal one)  fake pretty well the signal events Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  17. Parents of background leptons The most probable parents of fake electrons are neutral pions (πºe+e-) muons  are charged pions The most probable grandparents of fake electrons are strings (Lund model), ρ+,η, ω, Δ0 ,Δ+ muons  are strings (Lund model), ρ0, ρ+, ω Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  18. Cuts for mini-bias and QCD processes(including the signal one) The following cuts were applied to the minimum bias and QCD sample: 1. selection of events with the only 2 leptons, having El > 0.2 GeV, PTl > 0.2 GeV; 2. these 2 leptons have charges of the opposite charge; 3. the vertex of lepton origin lies within the R< 15mm from the interaction point; 4.Minv(l +l-) ≥ 0.9 GeV; 5. leptons have to satisfy the isolation criteria: the summed energyof particles E sum< 0.5 GeVwithin the cone of R isolation = √ Δη2+Δφ2= 0.2. Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  19. Lepton (µ) isolation criteria The plots show the distributions over summarized energy of the final state particles in the cones of radius R isolation = √ η2+φ2 respect to the (η – pseudorapidity) upper plot signal events bottom plot Mini-bias background Isolation criteria (R isolation = 0.2 ) E (of particles) = 0.5 GeV allows to separate 100% of Mini-bias bkg leptons with the loss of 8% of signal events (after applied 3 cuts discussed above + cut M inv (l+,l-) > 0.9) Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  20. Efficiency of cuts in the presence of mini-bias and QCD bkgd & S/B ratio • The total loss of signal events after application of all five cuts is expected to be about 20%. • So, we can expect to gain a huge sample of about 7x106 signal dilepton events per 1 year (107 sec.) Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  21. Conclusion The proposed cuts: 1. Events with only2leptons havingEl > 0.2 GeV, PTl > 0.2 GeV; 2. The charges of these 2 leptons have opposite sign; 3. The vertex of origin lies within thedistance < 15 mm fromthe interaction point 4. Minv(l +,l -) > 0.9 GeV 5. Isolation criteria E (R isolation = 0.2)= 0.5 GeV allow: I. To gainabout 7x106 signaldilepton events per 1 year; II. To suppress QCD & Mini-bias bkgd: completely for muons and to S/B = 9 for electrons; III. Next step: full detector MC simulation. Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  22. J/Ψ production processes (benchmark process) 1) q i q i¯ ̽ c c¯  J/Ψ  l +l -+ X 86 ) g g  J/Ψ + g  l +l - + X R.Baier and R.Rücke, Z.Phys. C19(1983) 251 106) g g  J/Ψ +  l +l -+ X M.Drees and C.S.Kim, Z.Phys. C53 (1991) 673 421) g g  cc¯ [3S 1 (1) ] g ll + X 422) g g  cc¯ [3S 1 (8) ] g ll + X 423) g g  cc¯ [3S 0 (8) ] g ll + X 424) g g  cc¯ [3P J (8) ] g ll + X 425) g q  cc¯ [3S 1 (8) ] q ll + X 426) g q  cc¯ [3P J (8) ] q ll + X 427) g g  cc¯ [3S 1 (1) ] q  ll + X 428) q q¯ cc¯ [3S 1 (8) ] g  ll + X 429) q q¯ cc¯ [1S 0 (8) ] g  ll + X 430) q q¯ cc¯ [3P J (8) ] g  ll + X 431) g g  cc¯ [3P 0 (1) ] g  ll + X 432) g g  cc¯ [3P 1 (1) ] g  ll + X 433) g g  cc¯ [3P 2 (1) ] g  ll + X 434) g q  cc¯ [3P 0 (1) ] q ll + X 435) g q  cc¯ [3P 1 (1) ] q  ll + X 436) g q  cc¯ [3P 2 (1) ] q  ll + X 437) q q  cc¯ [3P 0 (1) ] g  ll + X 438) q q¯  cc¯ [3P 1 (1) ] g  ll + X 439) q q¯  cc¯ [3P 2 (1) ] g  ll + X G.T.Badwin, E.Braten and G.P.Lepage, Phys.Rev. D51 (1995) 1125]; M.Beneke, MKrämer and M.Vänttinen, Phys.Rev.D57 (1998) 4258; B.A.Kniehl and J.Lee, Phys.Rev. D62 (2000) 114027 Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  23. J/Ψ production The main contributions to the cross section give the following processes: 1) qi qi¯  ̽ c c¯  J/Ψ  l+ l - + X 428) q q¯  cc¯ [3S1(8)] g  l+ l- + X 430) q q¯  cc¯ [3PJ(8)] g  l+ l- + X The maximum cross section value (obtained by PYTHIA 6.4 simulation) is σ = 20.75 pb that corresponds to 358.5 events / day for the E beam = 14 GeV and Luminosity = 2*105 1/mb*sec (= 2*1032 cm-2 sec-1) Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  24. Signal l± : (l = μ,e) l -- left, l +- right: • 0 ≤ El≤ 10 GeV, < El> = 4.4 GeV • 0≤ PTl ≤ 2 GeV, < PTl> = 1.2 GeV PTlpeak = 1.4 GeV • < Θl> = 27.2 ° some Θl >90° Important: The same range of angle distributions Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  25. Signal l± : (l = μ,e) FastSim l -- left, l +- right: • 0 ≤ Pz≤ 10 GeV, < Pz> = 4.2 GeV • -2≤ Px, Py ≤ 2 GeV Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  26. Signal l± : (l = μ,e) FastSim l -- left, l +- right: • 0 ≤ P, El, ≤ 10 GeV, < P, El> = 4.4 GeV • 0≤ PTl ≤ 2 GeV, < PTl> = 1.2 GeV PTlpeak = 1.4 GeV Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  27. Signal l±Fastsim l -- left, l +- right: • < Θl> = 27.2 ° some Θl >90° Important: The same range of angle distributions Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

  28. Outline

  29. I. Antiproton beam with Ebeam < 15 GeVmay provide an interesting information about quark dynamics inside the hadron andproton structurein the energy region where the Perturbative QCD comes intointerplay with a reachresonance ( i.e.Nonperturbative ) physics. II. Different to electron beams, used for measurements of proton structure functions in the region of !negative!values of the square of transferred momentum (q2< 0, “space-like” region), antiproton-protoncollisionsallow to make measurements of proton structure functions in the region of !positive! values of the square of the transferred momentum (q2 > 0, “time-like”, region, which is less studied ! ). Anna Skachkova : “Muon pairs production at PANDA”, 12.12.2010 , Obninsk

More Related