Standard Model Tests at the LHC A. Salzburger, CERN on behalf of the - PowerPoint PPT Presentation

Standard Model Tests at the LHC A. Salzburger, CERN on behalf of the ATLAS and CMS collaborations

2009 900 GeV LHC Run-1 and Run-2 2.76 TeV 2010 main Run-1 dataset 2011 7 TeV 2012 8 TeV Run-2 has started 13 TeV 2015 2 A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015

LHC - The main experiments A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 A T oroidal L HC A pparatu S + ALFA length ~40 m, height ~22 m, weight ~7000 tons Inner Tracker embedded in 2 T solenoid, sampling EM calorimeter, 
 MS tracker/spectrometer within a toroidal magnetic system C ompact M uon S olenoid length ~ 22 m, height ~ 12.5 m, weight ~12500 tons Full Silicon Inner Tracker embedded 5 T solenoid, crystal EM calorimeter A L arge I on C ollider E xperiment dedicated for Pb-Pb collisions, high particle identification capability LHCb dedicated for studying properties of the B-mesons, movable precision silicon pixel detector very close to the interaction region TOTEM roman pot detectors located 150/220 m from the CMS interaction point 3

Foundation - detector performance A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 ‣ presented results rely on a very deep understanding and precise modelling of the experimental setups - impressive results from the performance/physics objects groups - in general, exceptional Monte Carlo detector modelling of the data CMS 2011 #modules 300 µ Data: RMS = 0.4 m µ MC Ideal: RMS = 0.3 m 250 µ MC Realistic: RMS = 0.3 m 200 150 BPIX 100 50 0 10 -10 -5 0 5 ) [ µ m] median(u -u hit pred CMS Tracker alignment ATLAS EM electron scale CMS 2011 4

Detector performance & data taking efficiency A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 ‣ presented results would not have been possible without - excellent performance of the LHC - very high data taking efficiency and stable detector operation of the LHC experiments ‣ gives a lot of confidence for Run-2 Very similar numbers for all experiments ALICE dE/dx in TPC

the new kid 6 A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015

All spot-on - all done ? A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 ‣ Run-1data has still a lot of interesting physics - QCD - become more and more precision measurements ‣ Soft QCD : minimum bias, underlying event measurements necessary in pp conditions ‣ Hard QCD: test of high order pertubative QCD 
 (inclusive, multiple-jet production cross-sections V+jets production) ‣ precision measurement of fundamental parameters α s ‣ constraining the parton density functions (PDFs) - EWK observables and processes ‣ Z A fb ‣ VBF/VBS results (observation and evidence) - precision measurements to come, such as m W ‣ Run-2: 13 TeV measurements are on the way - back to the start, do it again and confirm (or not) - will show some hot-of-the-press results, many more to follow in the next months

Total inelastic cross section A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 -1 ATLAS Preliminary s = 13 TeV, 63 b µ Data ‣ inelastic cross section measurements 
 Kopeliovich et. al [32] are essential Menon et. al [33] Khoze et. al [34] Gotsman et. al [35] ‣ very precise measurements for 
 Fagundes et. al [36] 7 TeV and 8 TeV 60 65 70 75 80 - supplemented by TOTEM measurement [mb] σ inel ‣ first 13 TeV result from ATLAS - using Minimum Bias 
 Scintillator detectors and extrapolated 
 to total cross section - ratio measurement 
 single sided counter/ 
 inclusive counters 73 . 1 ± 0 . 9 (exp.) ± 6 . 6 (lum.) ± 3 . 8 (extr.) mb. 8 ATLAS-CONF-2015-038

Soft QCD - Minimum bias measurements A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 ‣ Why measuring the charged particle multiplicities ? - pertubative QCD describes 
 only hard-scatter partons, 
 rest described by 
 phenomenological models Non-diffractive Single-diffractive Double-diffractive ‣ ND component - QCD motivated models with many parameters - these parameters have impact when extrapolated to high Q (e.g. color reconnection) ‣ SD & DD component not well constraint and little data available ‣ Measure primary charged particle distribution to constrain models - model independent (e.g. no SD/DD/ND splitting), corrected to particle level dN ev /dn ch , <pT> vs. n ch , dN ch /d η , d 2 N ch /d η dp T 9

Minimum bias measurement - CMS/TOTEM A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 ‣ charged particle measurement - track counting measurement with corrections track reconstruction e ffi ciency (dominant) fake/ghost tracks (not an issue in μ =0) trigger, vertex, selection e ffi ciency contamination of pile-up events - unfolding to particle level usually done using a Bayesian unfolding ‣ CMS combined with TOTEM - test model dependence up to |eta| ~ 6.5 - good modelling with QGSJetII-04 up to large pseudo-rapidity 10 Eur. Phys. J. C 74 (2014) 3053

Minimum bias measurement - ATLAS A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 ‣ recent 13 TeV measurement of ATLAS - challenging due to newly installed innermost pixel detector (IBL) many checks needed to understand the material budget of new detector - phase-space: N ch ≥ 1, p T > 500 MeV, | η | < 2.5 ‣ Good modelling by EPOS (LHC tune) and PYTHIA8 (A2 tune) 4 ] η -2 = 0 2 n 1, p > 500 MeV, | | < 2.5 10 ≥ η [ GeV / d n 1, p > 500 MeV, | | < 2.5 ch ≥ η 4 T p > 500 MeV, n 1 ≥ ch Data T 10 ATLAS Preliminary s = 13 TeV ch ch η T ATLAS Preliminary s = 13 TeV N PYTHIA8 A2 1  d T ATLAS Preliminary 3.5 p 3.5 η ⋅ PYTHIA8 Monash d − 1 10 η ev / d N / d HERWIG++ UE-EE5 − 2 10 1/ 3 ch EPOS LHC − 3 10 N ch QGSJET II-04 2 − 4 ) d 10 3 N 2.5 T − 5 10 p d π − 6 1/(2 10 Data ⋅ 2 7 − PYTHIA 8 A2 ev 10 Data 2.5 ev PYTHIA 8 Monash 8 − N 10 N PYTHIA 8 A2 1.5 HERWIG++ UE-EE5 1/ 1/ − 9 PYTHIA 8 Monash 10 EPOS LHC HERWIG++ UE-EE5 10 − 10 QGSJET II-04 1 EPOS LHC − 11 2 10 QGSJET II-04 1.5 2.5 2 1.5 1 0.5 0 0.5 1 1.5 2 2.5 1.2 MC / Data MC / Data 1.5 1 1 0.5 0.8 1 1 10 2.5 2 1.5 1 0.5 0 0.5 1 1.5 2 2.5 − − − − − 3 4 10 10 p [GeV] η T s [GeV] 11 ATLAS-CONF-2015-028

Soft QCD - Underlying event analyses C#Z#Boson# C#Leading#Track# A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 C#Leading#Jet# ‣ Underlying event (UE) comprises all particles 
 except those from the hard process of interest - performed within different azimuthal regions - Studying the UE at different processes and energies ‣ Modern tunes describe energy dependence very well - UE consistent between different processes within known selection biases CMS Transverse density > [GeV] )] 3.5 ATLAS φ s = 7 TeV Transverse region 1.2 ∆ s = 7 TeV ( -1 Data 2011: Z events (4.6 fb ) ∆ 3 η -1 Data 2010: Minimum bias and jet events (168 -1 , 37 pb ) µ ∆ /[ 1 φ 〉 ch δ 2.5 N η s = 2.76 TeV 〈 δ 0.8 / 2 T p 2 Leading jet: > [GeV] ∑ 1.8 0.6 | | < 2, p > 1 GeV η 1.5 T < 1.6 φ Charged particles: δ 1.4 η | η | < 2, p > 0.5 GeV δ 1.2 / T 0.4 T 1 p 1 ∑ Minimum bias events < 0.8 Data s = 0.9 TeV 0.6 PYTHIA 6 Z2* Jet events 0.4 0.2 0.5 0.2 PYTHIA 8 CUETP8S1 Z events 0 5 10 15 20 25 30 35 40 45 50 p [GeV] HERWIG++ UE-EE-5C T 0 0 50 100 150 200 250 300 350 400 450 500 0 20 40 60 80 100 jet p [GeV] leadjet leadtrack p Z or p or p [GeV] T T T T √ 12 Eur. Phys. J.C(2014)74:3195 CERN-PH-EP-2015-176

arXiv:1504.00024 ! Soft QCD - particle production A. Salzburger - Standard Model Measurements at the LHC - Matter to the Deepest, Ustron, 2015 ‣ Measurement of particle spectra and species give additional input to understand/ constraint the modelling - soft parton interactions - hadronisation process ‣ ALICE measurement of prompt hadrons 
 ( π ± ,K ± ,p,p) at 7 TeV - combination of 5 techniques (sub-detectors) 
 for particle identification ‣ Shapes of spectra are reasonably well described by most modules - no model can simultaneously describe the yield of 
 the different particle types 13 arXiv:1504.0024