Particle spectra in Minimum Bias events at 13TeV

Transcription

1 Particle spectra in Minimum Bias events at TeV Juan Manuel Grados Luyando on behalf of the CMS collaboration Deutsches Elektronen-Synchrotron, Hamburg 05 Trieste, Italy

2 Motivation Probe the different components of hadron production The transition from the perturbative to the non-perturbative region Behaviour of QCD at small-x Multiple parton interactions Saturation of parton densities Soft diffractive components Tune the modeling of these contributions Center-of-mass energy dependence Taming of the cross section in the low pt region Juan Manuel Grados Luyando Trieste, Italy November 05

3 Multiple Parton Interactions Multiple Parton Interactions Soft to semi-hard interactions Phenomenological models Tuning of the model parameters based on experimental data Comparison to the new CMS tunes Simultaneous fits to CDF UE data at and.96 TeV, and CMS UE at 7 TeV Energy dependence of the MPI parameters Different parton densities Theoretical uncertainties from allowed parameter space Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05

4 Pseudorapidity at 0T Measurement of pseudorapidity distribution of charged hadrons in proton-proton collisions at s = TeV Presented for inelastic events No minimum transverse momentum requirement (measurement done at 0T) Corrected to primary long-lived charged hadrons CMS pp s = TeV 0.0 fraction data PYTHIA8 CUETP8M EPOS LHC number of reconstructed tracks Phys. Lett. B 75 (05) 6 Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05

5 Pseudorapidity at 0T Measurement of pseudorapidity distribution of charged hadrons in proton-proton collisions at s = TeV Presented for inelastic events No minimum transverse momentum requirement (measurement done at 0T) Corrected to primary long-lived charged hadrons (no leptons) dn ch /dη Charged-particle multiplicity, s = TeV Data CUETP8S-CTEQ6L CUETP8M PYTHIA8 Tune C η PHYTHIA8 (CUETP8M and CUETP8S) and EPOS LHC agree with the measurement within the error bands Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 Phys. Lett. B 75 (05) 6 5

6 Pseudorapidity at 0T Measurement of pseudorapidity distribution of charged hadrons in proton-proton collisions at s = TeV Presented for inelastic events No minimum transverse momentum requirement (measurement done at 0T) Corrected to primary long-lived charged hadrons PHYTHIA8 (CUETP8M and CUETP8S) and EPOS LHC agree with the measurement within the error bands Phys. Lett. B 75 (05) 6 Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 6

7 Pseudorapidity at 8 TeV Measurement of pseudorapidity distribution of charged particles in proton-proton collisions at s = 8 TeV Presented for different diffractive event selections (TOTEM event selection) Corrected down to zero transverse momentum Corrected to all charged particles TOTEM acceptance: 5. < η < 6. dn ch /dη Inclusive pp CMS-TOTEM, - s = 8 TeV, L = 5 µb dn ch /dη NSD-enhanced pp CMS-TOTEM, - s = 8 TeV, L = 5 µb dn ch /dη SD-enhanced pp 5 CMS-TOTEM, - s = 8 TeV, L = 5 µb Data Pythia6 Z* Pythia8 C Herwig++ EE-CTEQ6L EPOS LHC QGSJetII-0 5 Data Pythia6 Z* Pythia8 C Herwig++ EE-CTEQ6L EPOS LHC QGSJetII-0 5 Data Pythia6 Z* Pythia8 C Herwig++ EE-CTEQ6L EPOS LHC QGSJetII-0 in 5.<η<6.5 or -6.5<η<-5. N ch N ch in 5.<η<6.5 and -6.5<η<-5. in only 5.<η<6.5 or only -6.5<η<-5. N ch MC / Data MC / Data. MC / Data η η η Eur. Phys. J. C (0) 7:05 Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 7

8 Pseudorapidity at 8 TeV Measurement of pseudorapidity distribution of charged particles in proton-proton collisions at s = 8 TeV Presented for different diffractive event selections (TOTEM event selection) Corrected down to zero transverse momentum Corrected to all charged particles TOTEM acceptance: 5. < η < 6. (dn ch )/d( η ) MC/data CMS+TOTEM, dn ch /d( η ) s = 8TeV,Inclusivepp CMS+TOTEM data CUETP6S CUETP8S-CTEQ6L CUETP8S-HERAPDF.5LO CUETP8M η (dn ch )/d( η ) MC/data CMS+TOTEM, dn ch /d( η ) s = 8TeV, NSD-enhanced CMS+TOTEM data CUETP6S CUETP8S-CTEQ6L CUETP8S-HERAPDF.5LO CUETP8M Results after tuning Eur. Phys. J. C (0) 7:05 η (dn ch )/d( η ) MC/data CMS+TOTEM, dn ch /d( η ) s = 8TeV,SD-enhanced CMS+TOTEM data CUETP6S CUETP8S-CTEQ6L CUETP8S-HERAPDF.5LO CUETP8M η Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 8

9 Pseudorapidity Predictions Event selection We can implement a similar event selection but instead of TOTEM we use particles in the range < η < 5 (HF calorimeter) in the following way: Non-Single Diffractive enhanced: at least one particle with E>5GeV on each side. Single Diffractive enhanced: at least one particle with E>5GeV on one side. Other side no particle with E>5GeV. Inelastic enhanced: at least one particle on either side with E>5GeV. Particle selection pt > 500MeV Final State Charged particles Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 9

10 Pseudorapidity at.8t and diffractive events. Predictions T h e shape o f a l l t h e predictions for the inclusive and inelastic selections is very similar, only changing the predicted value by ~0.5 particles per η unit. For the NSD selection: PYTHIA8 Tunes predict the same shape with different values, while has a valley in the central region. dn N dη dn N dη Selection: inclusive pp P8-CUETP8M P8-C NSD enhanced: E part > 5GeVin 5 < η < and< η < 5 η dn N dη dn N dη inel. enhanced: E part > 5GeVin 5 < η < or< η < 5 P8-CUETP8M P8-C SD enhanced: E part > 5GeVineither 5 < η < or< η < 5 η For the SD selection: PYTHIA8 Tunes predict s i g n i fi c a n t l y d i f f e r e n t behaviour than P8-CUETP8M P8-C η P8-CUETP8M P8-C η Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 0

11 Integrated-pT Measuring on different diffractive event topologies Will provide further constrains for the models Show where each model does a good/bad description Integrated pt spectrum Total > partonic cross section: Divergent towards low pt > phenomenological factor [α s(p T,0 + p T )/α s(p T )][p T /(p T,0 + p T ) ] Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05

12 Integrated-pT at 8 TeV Integrated pt spectrum ) min T r(p 0 CMS pp s = 8 TeV N ch (p > 0 MeV) > 0 in 5. < η < 6.5 T Leading charged particles, η <. At s = 8 TeV the turn over happens at pt-min ~ 5GeV Data Pythia 6 Z* Pythia 6 CUET Pythia 6 (default, MPI on) Pythia 6 (default, MPI off) Pythia 6 (default, MPI off, no sat).5 MC scaled to data at p T, min = 9 GeV p T min [GeV] arxiv: Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05

13 Integrated-pT at 8 TeV Integrated pt spectrum ) min T r(p 0 CMS pp s = 8 TeV N ch (p > 0 MeV) > 0 in 5. < η < 6.5 T Leading charged particles, η <. At s = 8 TeV the turn over happens at pt-min ~ 5GeV Data Pythia 8 C Pythia 8 CUET Pythia 8 MONASH QGSJetII-0 EPOS LHC Herwig++ UE-EE-5C How does it look at different center of mass energies?? How does it look for different diffractive topologies?? MC scaled to data at p T, min = 9 GeV 0 p T min [GeV] arxiv: Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05

14 Integrated-pT at TeV. Predictions Selection: inclusive pp s = TeV CMS pp s = 8 TeV r(p Tmin ) P8-CUETP8M P8-C p Tmin [GeV] ) min r(p T N ch (p > 0 MeV) > 0 in 5. < η < 6.5 T Leading charged particles, η <. Data Pythia 8 C Pythia 8 CUET Pythia 8 MONASH QGSJetII-0 EPOS LHC Herwig++ UE-EE-5C MC scaled to data at p T, min = 9 GeV 0 p T min [GeV] Similar turn over value arxiv: Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05

15 Integrated pt leading distribution. Predictions For inclusive, inelastic enhanced and NSD samples the turn over happens at the same pt-min value Selection: inclusive pp inel. enhanced: E part > 5GeVin 5 < η < or< η < 5 NSD enhanced: E part > 5GeVin 5 < η < and< η < 5 r(p Tmin ) 0 0 P8-CUETP8M P8-C r(p Tmin ) 0 0 P8-CUETP8M P8-C r(p Tmin ) 0 0 P8-CUETP8M P8-C p Tmin [GeV] p Tmin [GeV] p Tmin [GeV] Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 5

16 Integrated pt leading distribution. Predictions SD enhanced Sensitive to smaller effective CM energy M x <s Turn over happens at smaller values of pt-min r(p Tmin ) Measuring the as a function of Mx one can a c c e s s t h e e n e r g y dependence of saturation scale r(p Tmin ) SD enhanced: E part > 5GeVineither 5 < η < or< η < 5 0 P8-CUETP8M P8-C p Tmin [GeV] Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 6

17 Integrated pt leading distribution. Predictions NSD enhanced: E part > 5GeVin 5 < η < and< η < 5 SD enhanced: E part > 5GeVineither 5 < η < or< η < 5 r(p Tmin ) 0 0 P8-CUETP8M P8-C r(p Tmin ) P8-CUETP8M P8-C NSD extends to higher pt-min values p Tmin [GeV] Turn over shifted to small pt-min p Tmin [GeV] Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 7

18 Summary Pseudorapidity distribution at s = TeV for inclusive events Predictions for the pseudorapidity density at s = TeV for different event selections New proposal for extracting information about the energy dependence of the saturation scale Experimental results to be released soon Juan Manuel Grados Luyando MPI@LHC Trieste, Italy November 05 8