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Multiple Partonic Interaction measurements at LHCb

Multiple Partonic Interaction measurements at LHCb. Raluca Muresan Horia Hulubei National Institute of Physics and Nuclear Engineering On behalf of the LHCb collaboration. Measuring Multiple Partonic Interactions at the LHC Research Workshop of the Israel Science Foundation

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Multiple Partonic Interaction measurements at LHCb

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  1. Multiple Partonic Interaction measurements at LHCb Raluca Muresan HoriaHulubei National Institute of Physics and Nuclear Engineering On behalf of the LHCb collaboration Measuring Multiple Partonic Interactions at the LHC Research Workshop of the Israel Science Foundation 14-18 October 2012, Tel Aviv, Israel

  2. Disclaimer This talk represents a collections of LHCb results: soft-QCD, EW, charm production relevant for the MPI models, rather than a collection of measurements of the MPI observables and their interpretation. The list might not be exhaustive and some of the results presented are flashed or only hinted at. R. Muresan - MPI at LHCb

  3. LHCb detector Designed to look for physics beyond the SM by studies of CPviolation and raredecays usingb & c hadrons JINST 3 (2008) S08005. R. Muresan - MPI at LHCb

  4. LHCb detector • Forward coverage • 15-300(250) mrad, high precision tracking and vertexing, • excellent PID • Perfect tool for a large variety of physics studies in the forward region JINST 3 (2008) S08005. R. Muresan - MPI at LHCb

  5. Unique space coverage LHCbfully instrumentedinanhrangefrom 2 to 5. Forward region particularly sensitive to MPI and low Bjorken-x QCD dynamics R. Muresan - MPI at LHCb

  6. LHCb data 0.9 TeV 0.31 nb−1; 2.76 TeV 100 nb−1; 37.5 pb−1 7 TeV (2010) pA data taking planed for the beginning of the next year R. Muresan - MPI atLHCb

  7. Large coverage in rapidity loss 0.9 TeV & 2.76 TeV farther from the beam in y; 7 TeV & 8 TeV, overlap in rapidity loss; probing energy scale violation. R. Muresan - MPI at LHCb

  8. P. Skands R. Muresan - MPI at LHCb

  9. LHCb - soft QCD results • KS0x-section @ 0.9 TeV, PLB 693 (2010) 69-80; • V0 ratios: baryon vs. meson suppression & baryon number transport at @ 0.9 TeV and 7 TeV;JHEP 1108 (2011) 034. • ϕ cross-section @ 7 TeV; PLB 703 (2011) 267-273. • Charged particle multiplicities @ 7 TeVEPJC 72 (2012) 1947 • Measurement of forward energy flow LHCb-CONF-2012-012 @ 7 TeV • Particle ratios at 0.9 & 7 TeV, arXiv:1206.5160 (accepted EPJ. C) R. Muresan - MPI at LHCb

  10. Multiplicity studies • Particles counted using the tracks in Vertex Locator: high efficiency, minimal material interaction, partial backward coverage, but no momentum measurement. • Prompt charge particle production e, μ, p ,K, p with sum average proper lifetimes of the ancestors < 10ps. • 2 x 1.5 M events, both magnet polarities were used. Eur. Phys. J. C 72 (2012) 1947 R. Muresan - MPI at LHCb

  11. Multiplicity studies Eur. Phys. J. C 72 (2012) 1947 Charged particle densities Several generators & tune predictions were compared to the data; none are able to describe them fully; as a general trend the multiplicity and charged particle densities are underestimated Multiplicity distributions R. Muresan - MPI at LHCb

  12. Forward energy flow • Energy flow (EF) @ high η - directly sensitive to the amount of parton radiation and Multiple Parton Interaction (MPI). • EF measurements results useful both for the collision physics and for the ultra-high energy cosmic-ray interaction models. • EF defined as: dEtot is the total energy of stable particles in the ηbin Nintnumber of inelastic pp interactions Experimentally determined for a Δη bin: Ei,ηenergy of an individual particle LHCb-CONF-2012-012 R. Muresan - MPI at LHCb

  13. Data and event sample • Inclusive MB at least one track p>2 GeV/c • Hard scattering at least one track pT > 3 GeV/c • Diffractive enriched inclusive MB with no tracks in −3.5<η<−1.5 • Non-diffractive enriched inclusive MB with at least one track in −3.5<η<−1.5 • 0.1 nb-1 low luminosity LHC run @7 TeV • Events with at least one well reconstructed track Correction for detector effects - bin-by-bin from simulation • Systematic uncertainties: • tracking • multiple interaction events (5% of events) • simulation model LHCb-CONF-2012-012 R. Muresan - MPI at LHCb

  14. Total forward energy flow LHCb-CONF-2012-012 Corrected total EF compared with PYTHIA generator predictions. Total EF underestimated at high η by all the PYTHIA6 tunes used and for all event categories studied. PYTHIA 8 describes well the total EF for diffractive enriched events. Similar conclusions hold for charged energy flow R. Muresan - MPI at LHCb

  15. Total forward energy flow LHCb-CONF-2012-012 Corrected total EF compared with cosmic ray generators predictions. Cosmic-ray models overestimate the total EF. SYBILL/EPOS gives the best description of the total EF for inclusive MB events. QGSJETII-03 gives reasonable description of the total EF for hard scattering events. R. Muresan - MPI at LHCb

  16. Prompt hadron production ratios • 0.3 nb-1 of data @0.9 TeV and 1.8 nb-1@7 TeV low int LHC run. • Simulated events used to calculate efficiencies and estimate systematic uncertainties. • PID calibration using data samples of • Corrections applied for: • effects of non-prompt contamination, • geometrical acceptance losses, • track finding inefficiency. • Systematic uncertainties: • PID (most important – size of calibration sample) , • interaction x-section & amount of material, • tracking & non-prompt contamination. arXiv:1206.5160 R. Muresan - MPI at LHCb

  17. Same particle ratios arXiv:1206.5160 0.9 TeV 7 TeV 0.9 TeV 7 TeV The ratios differ from unity especially at high pT and high η. The behaviour is well described by all the generator tunes. R. Muresan - MPI at LHCb

  18. Strange vs. up/down particles arXiv:1206.5160 Tendency for data to lie significantly higher than Perugia 0 and Perugia NOCR PYTHIA 6 tunes, excess strangeness being produced compared to some MC predictions. 0.9 TeV 7 TeV R. Muresan - MPI at LHCb

  19. Strange vs. up/down particles arXiv:1206.5160 Tendency for measurements to lie significantly higher than Perugia 0 and Perugia NOCR tune, excess strangeness seems to be produced compared to some MC predictions. 0.9 TeV 7 TeV φ cross-section measurement Phys.Lett. B703 (2011). R. Muresan - MPI at LHCb

  20. Baryon suppression arXiv:1206.5160 Data lie in most cases significantly higher than predictions – especially at high pTand high η. 0.9 TeV 7 TeV R. Muresan - MPI at LHCb

  21. Baryon suppression Data lie in most cases significantly higher than predictions – especially at high pTand high η. arXiv:1206.5160 7 TeV 0.9 TeV JHEP 1108 (2011) 034 R. Muresan - MPI at LHCb

  22. Baryon transport arXiv:1206.5160 At 0.9 TeV the ratio  from 0.8 to 0.4 in the highest pT and η bin. Data usually below LHCb MC and Perugia 0 predictions closer to Perugia NOCR PYTHIA 6 tunes 0.9 TeV 7 TeV R. Muresan - MPI at LHCb

  23. Baryon transport arXiv:1206.5160 At 0.9 TeV the ratio  from around 0.8 to around 0.4 in the highest pT and η bin. Data below LHCb MC and Perugia 0 predictions closer to Perugia NOCR 0.9 TeV 7 TeV JHEP 1108 (2011) 034. R. Muresan - MPI at LHCb

  24. Baryon transport vs. rapidity loss arXiv:1206.5160 LHCb results cover a larger rapidity loss than any other single experiment and significantly improve the measurement precision in the region Δy = yb-y< 6.5. JHEP 1108 (2011) 034 R. Muresan - MPI at LHCb

  25. EW results • LHCb probes two x-Q2 regions: • Medium Q2 (104 GeV2): • Z,W measurements x= 1.6 x10-4; • Low Q2 (~ 25 GeV2): • Drell-Yan ( γ*) towards x= 8 x10-6 R. Muresan - MPI at LHCb

  26. EWmeasurements @ 7 TeV • Central exclusive di-m production LHCb-CONF-2011-022, 37 pb-1. • Z0x-section using Z0 -> t+t-LHCb-CONF-2011-041, 248 pb-1 (an update to bereleasedsoon LHCb-PAPER-2012-029, see for the moment LHCb-TALK-2012-254) • W & Z production: x-sections; differential x-sections; x-section ratios and lepton charge asymmetry arXiv:1204.1620 – accepted in JHEP (Z0 ->m+m-, W±-> m±n), 37pb-1. • x-section for Z0->e+e- production LHCb-CONF-2012-011, 945 pb-1. • Jet production in Z0/g*eventsLHCb-CONF-2012-016, 1.02 fb-1. • Low mass Drell Yan production LHCb-CONF-2012-013, 37pb-1. R. Muresan - MPI at LHCb

  27. Z0 Compared to NNLO and NLO predictionswithdifferent PDF for the proton. PDF uncertainty, evaluatedat the 68% CL. Differentialx-section in yZalso available spares & arXiv:1204.1620 arXiv:1204.1620, LHCb-CONF-2011-041, LHCb-CONF-2012-011 R. Muresan - MPI at LHCb

  28. W&Z arXiv:1204.1620 Z0 ->m+m- W+-> m+n W--> m-n Rw (W++W-)/Z0 W+/Z0 W-/Z0 R. Muresan - MPI at LHCb

  29. W&Z W differential x-section & RW as function of hm alsoavailable spares & arXiv:1204.1620 arXiv:1204.1620 R. Muresan - MPI at LHCb

  30. W&Z Theory using DYNNLO + MSTW08 @NNLO LHCB-TALK-2012-254 R. Muresan - MPI at LHCb

  31. Z0/g* +jet production Z0/g*->mm channel measurement, normalised to the total inclusive Z0/g*->mmx-section; 2.0 <h (μ)< 4.5, pT(μ) ≥ 20 GeV/c; dimuon 60 ≤M≤ 120 GeV/c2 Jets : • reconstructed using the anti-kT algorithm with R = 0.5, and corrected to the hadron level. • 2.0 <h < 4.5 and pT >10 GeV/c • separated from μ of the Z0/g* by a distance R(μ, jet) ≥ 0.4 in • η – φ space. Event display x-section ratio 0.229 ± 0.011 consistent with SM predictions LHCb-CONF-2012-016 R. Muresan - MPI at LHCb

  32. Z0/g* +jet production NLO prediction LHCb-CONF-2012-016 R. Muresan - MPI at LHCb

  33. Z0/g* +jet production LHCb-CONF-2012-016 R. Muresan - MPI at LHCb

  34. Inclusive low mass Drell-Yan production • 2 m final states: 2< h < 4.5 & 5 < M < 120 GeV/c2. • pm>10 GeV/c and pmT>3 GeV/c. For M>40 GeV/c2pmT>15 GeV/c. Extraction of signal yield uses a fit of the minimum muon isolation of the two muons i.e. fraction of the pT of the muon jet carried by the m. LHCb-CONF-2012-013 R. Muresan - MPI at LHCb

  35. Inclusive low mass Drell-Yan production LHCb-CONF-2012-013 R. Muresan - MPI at LHCb

  36. Inclusive low mass Drell-Yan production LHCb-CONF-2012-013 R. Muresan - MPI at LHCb

  37. Selected charm results @ 7 TeV • Cross-section measurements: e.g J/ψ EPJ.C 71 (2011) 1645. • Ratio of prompt χc to J/ψ production: arXiv:1204.1462. • Production asymmetrymeasurements: e.g. Ds- anti Ds: PLB 713 (2012) 186-195. • J/ψ pair production:PLB 707 (2012) 52–59, 37 pb-1. • Double charm production involving open charm:JHEP 06 (2012) 141, 355 pb-1. R. Muresan - MPI at LHCb

  38. J/ψ pair production PLB 707 (2012) Only statistical uncertainties Theoretical prediction from PRD 84 (2011) 094023 Production of J/ψ pairs has been observed with a statistical significance in excess of 6 σ R. Muresan - MPI at LHCb

  39. Double charm production JHEP 06 (2012) Measured cross-sections, charged conjugate modes are included Hatched areas: PRD 57 (1998) 4385 PRD 73 (2006) 074021. Shaded area: EPJC 61 (2009) 693 R. Muresan - MPI at LHCb

  40. Double charm production JHEP 06 (2012) Measured ratios charged conjugate modes are included Expectations from DPS using the x-section measured at Tevatron for multijet events Properties of J/ψC, CC and C-anti C events were studied: pT,, slope parameters of pTspectra, difference in azimuthal angle and y etc. see spares and JHEP. 06 (2012) 141. R. Muresan - MPI at LHCb

  41. Stay tuned !for our future resultsexploiting also the data @ 2.76 & 8 TeV &pA LHCb is not only a b&c-physics experiment but provides also an excellent environment for forward physics studies impacting on the MPI models Have a look to the full list of the LHCb papers & LHCb conference contributions R. Muresan - MPI at LHCb

  42. Spares R. Muresan - MPI at LHCb

  43. Forward charged energy flow Corrected charged energy flow compared with PYTHIA generator predictions. All PYTHIA 6 tunes used underestimate the charged EF at high η for all the type of events studied. PYTHIA 8 describes the best the charged EF for diffractive enriched events. LHCb-CONF-2012-012 R. Muresan - MPI at LHCb

  44. Forward charged energy flow Corrected charged EF vs. cosmic ray generators predictions. Cosmic-ray models overestimate the charged EF. SYBILL/EPOS best description of the inclusive MB charged EF. QGSJETII-03 reasonable description of the charged EF in hard scattering. Diffractive charged EF is underestimated by the cosmic-ray models LHCb-CONF-2012-012 R. Muresan - MPI at LHCb

  45. LHCb-MC & Perugia tunes • PYTHIA6 generates pp interactions up to hadronization; the CTEQ6L parametrisation for the PDFs. • EvtGen to generates the decay and evolution of all particles, B hadrons, generic and user/signal. • delegate to PYTHIA when decay not present in decay table • delegate to Photos for QED radiative corrections R. Muresan - MPI at LHCb

  46. LHCb-MC & Perugia tunes LHCb PYTHIA tune: • I. Belyaev et al., Handling of the generation of primaryevents in Gauss, the LHCb simulation framework, Nuclear Science Symposium Conference Record (NSS/MIC) IEEE (2010) 1155. PYTHIA usedwith • P. M. Nadolsky et al., Implications of CTEQ global analysis for collider observables, Phys. Rev. D78 (2008) 013004, arXiv:0802.0007. • M. Bengtsson and T. Sjostrand, Parton showers in Leptoproduction Events, Z. Phys. C37 (1988) 465. Tuning Monte Carlo Generators: The Perugia Tunes, Peter ZeilerSkands; Phys.Rev. D82 (2010) 074018 R. Muresan - MPI at LHCb

  47. Protons vs. kaons arXiv:1206.5160 0.9 TeV 7 TeV Agreement with simulation generally good, but results hard to interpret. R. Muresan - MPI at LHCb

  48. Theory prediction for the EW – W&Z production • The results are compared to theoreticalpredictionscalculatedat NNLO with the program DYNNLO (Phys. Rev. Lett. 98 (2007) 543 222002) for the NNLO PDF sets of MSTW08 (EPJC63 (2009) 189), ABKM09 (Phys. Rev. D81 (2010) 567 014032), JR09 (Phys. Rev. 569 D79 (2009) 074023), HERA15 (JHEP 01 (2010) 109) and NNPDF21 (Nucl. Phys. B838 (2010) 136) and at NLO for the NLO PDF set CTEQ6M (Phys. Rev. D78 (2008) 013004). R. Muresan - MPI at LHCb

  49. Z arXiv: 1204.1620 LHCb-CONF-2012-011 Consistent to each other and to NNLO predictions. R. Muresan - MPI at LHCb

  50. W arXiv: 1204.1620 R. Muresan - MPI at LHCb

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