Soft QCD WG Summary Xavier Janssen, Anna Kulesza, Andrew Pilkington - PowerPoint PPT Presentation

Soft QCD WG Summary Xavier Janssen, Anna Kulesza, Andrew Pilkington QCD@LHC 2011 St Andrews – Scotland – 8/26/2011 X. Janssen - 8/26/2011 1/12 QCD@LHC 2011 – Soft QCD Summary

Contributions Thanks to all speakers and apologize for not covering everything X. Janssen - 8/26/2011 2/12 QCD@LHC 2011 – Soft QCD Summary

Contributions We will rather go through some topics that leaded to discussions and for which further work is needed Thanks to all speakers and apologize for not covering everything X. Janssen - 8/26/2011 3/12 QCD@LHC 2011 – Soft QCD Summary

Scope of “Soft QCD WG” The majority of the pp collisions are soft → no hard parton scattering → no “perturbative” predictions → need to model them phenomenologically Can we come up with measurements addressing this ? X. Janssen - 8/26/2011 4/12 QCD@LHC 2011 – Soft QCD Summary

LHC Results: MinBias and UE Plenty of results from ATLAS/CMS (see plenary talks) and ALICE/LHCb: Compare data to other MC e.g. Publish “corrected” data in HEPData/Rivet different hadronization models, ... * Only corrected results useful for * Only corrected results useful for * Solved via Rivet (but slow) ! comparison to theory/models comparison to theory/models * Best would be if experiments do it directly * Rivet default in ATLAS/CMS for new * Rivet default in ATLAS/CMS for new standard model analysis approval standard model analysis approval Study particle flavour in UE What about LHCb/ALICE results ? What about LHCb/ALICE results ? * From preliminary to papers, it takes time * From preliminary to papers, it takes time * Ongoing in some experiments …. (careful further cross-checks performed) (careful further cross-checks performed) X. Janssen - 8/26/2011 5/12 QCD@LHC 2011 – Soft QCD Summary

LHC Results: Identified Particles Other measurements to be performed to understand these effects: * Lambda / Lambda_bar ratios at central rapidity from CMS/ATLAS/ALICE * Correlations for identified particles: Kaons, Lambdas, … X. Janssen - 8/26/2011 6/12 QCD@LHC 2011 – Soft QCD Summary

LHC Results: Correlations Craig Buttar Δϕ Correlations (cresp) Correlations (vs) MC tuning: → Identify parameters to vary to discriminate between component: e.g. pT cut to remove soft contribution, include hard scale, … → Study of forward-backward correlations to probe MPI (dominant at large ∆η ) Cluster model fit: → Do we have to use another functional form ICM Fit X. Janssen - 8/26/2011 7/12 QCD@LHC 2011 – Soft QCD Summary

LHC Results: High Multiplicity Events Craig Buttar High Multiplicity events studies to do: * Redo ALICE analysis (BEC, J/Psi, …) in CMS and ATLAS if possible * s/u ratio (vs) multiplicity * particle flavour composition (in jets) vs multiplicity * properties of jets (constituent, brodening, …) vs multiplicity X. Janssen - 8/26/2011 8/12 QCD@LHC 2011 – Soft QCD Summary

LHC Results: Forward and Diffraction Diffraction – how to make the most useful measurements? SD x-section extrapolated by MC ! X. Janssen - 8/26/2011 9/12 QCD@LHC 2011 – Soft QCD Summary

Monte-Carlo tuning and Model building + Status of MC tunes in CMS (Rick Field) + Energy dependent Herwig++ tunes (C. R ö hr) X. Janssen - 8/26/2011 10/12 QCD@LHC 2011 – Soft QCD Summary

Monte-Carlo tuning and Model building Should we maintain so many tunes of PYTHIA 6&8, HERWIG(JIMMY/++), Sherpa ... ? A. Buckley Answer: No, we should stop using discarded ones for good reason ! X. Janssen - 8/26/2011 11/12 QCD@LHC 2011 – Soft QCD Summary

Monte-Carlo tuning and Model building Why should we produce new tunes based on LHC data ? Answer 1: To be able to describe pile-up at LHC and do searches Answer 2: Identify places where the MC are failing (and maybe try to develop/test/use other/better models) R. Field (Lam+LamBar) Rapidity Distribution: dN/dY 0.25 _ CMS Data ( Λ + Λ ) PYTHIA Tune Z1C 7 TeV Charged Particle Rati 0.20 0.15 0.10 900 GeV Tune Z1C 0.05 qq/q: 0.1 -> 0.12 NSD (all pT) us/s: 0.4 -> 0.8 0.00 -4 -3 -2 -1 0 1 2 3 4 Rapidity Y PT Particle Ratio: Kaons/Pions 0.60 ALICE Data (K + +K - )/( π + + π - ) PYTHIA Tune Z1 & Z1C PT Particle Ratio 0.40 Z1C Z1 0.20 Tune Z1C qq/q: 0.1 -> 0.12 900 GeV us/s: 0.4 -> 0.8 INEL (|Y| < 0.75) 0.00 0 1 2 3 4 PT (GeV/c) X. Janssen - 8/26/2011 12/12 QCD@LHC 2011 – Soft QCD Summary