ELECTROWEAK AND TOP RESULTS AT LHC Jose Enrique Garcia – IFIC-Valencia

Electroweak and Top cross-sections JOSE ENRIQUE GARCIA 2

ELECTROWEAK

Electroweak 1 Electromagnetic and Weak probes in hadron-hadron collisions Clean signature with lepton/photon/ETmiss 2 Benchmark of SM validation at high energy Large mass of W/Z assures hard scale involved 3 Measurements at extreme kinematic topologies allow tuning of MC tools (N)NLO calculations, MC event generators 4 Crucial in searches for Beyond-SM physics Signal typically involves W/Z/… JOSE ENRIQUE GARCIA 4

INCLUSIVE W/Z Special data with low pile-up arXiv:1402.0923 JOSE ENRIQUE GARCIA 5

W+JETS Important background for many processes, it needs to be properly modeled. Comparison with different generators : NLO BLACKHAT+Sherpa does a good job for most of the distributions Discrepancy observed for ET sum of all jets (ST in ATLAS, HT in CMS) ATLAS-CONF-2014-035 arXiv:1406.7533 JOSE ENRIQUE GARCIA 6

W+JETS Discrepancy also seen in : dijet mass, Δφ(jet1,μ) Data are crucial input for tuning MC generators ATLAS-CONF-2014-035 arXiv:1406.7533 JOSE ENRIQUE GARCIA 7

W+bb Largest background for top-quark pair production Well separated 2 b-jets ⟶ less theoretical uncertainty arXiv:1312.6608 PLB735 (2014) 204 Theory : Conclusion? similarly ATLAS W+b : JHEP06 (2013) 084 JOSE ENRIQUE GARCIA 8

WW Parallel session talk ATLAS-CONF-2014-033 LHC measurements showed an enhancement of data compared to theory in the di-boson x-section. Latest measurement made it more evident : Parallel session talk Check conf Possible issues : → Experimental systematics? → Higher-order corrections beyond NLO QCD? → Theoretical uncertainty for calculation of jet veto (NNLL resummation)? JOSE ENRIQUE GARCIA 9

WW SCATTERING final states : W±W± jj→l±ν l±ν jj (l=e, μ) ATLAS : arXiv:1405.6241 final states : W±W± jj→l±ν l±ν jj (l=e, μ) Very rare SM process and can be used as test for BSM, first evidence the VVVV vertex Challenging analysis due to dominant WW production (QCD) EWK-VBS First evidence for vector boson scattering Check CMS note ATLAS : 3.6σ/2.8σ(observed/expected) CMS: 2.0σ/3.1σ (observed/expected) JOSE ENRIQUE GARCIA 10

TOP

Theoretical Predictions TOP PRODUCTION AT LHC At the peak of instantaneous luminosity during 2012 the top production was : Around 15M quark tops were produced during 2011 and 2012! ~ 2 top pairs/s ~ 1 single top/s LHC Theoretical Predictions table with values?? references!!! s-channel1 t-channel2 Wt-channel3 top pairs4 7 TeV 8 TeV 1 Phys. Rev. D 81, 054028 (2010) 2 Phys. Rev. D 83, 091503(R) (2011) 3 Phys. Rev. D 82, 054018 (2010) 4 NNLO+NNLL (Top++2.0) JOSE ENRIQUE GARCIA 12

WHAT MAKES TOP QUARK INTERESTING? 1 Heaviest fundamental particle in the Standard Model Larger mass ➙ Larger coupling to SM Higgs + mtop is a fundamental parameter in SM Allows for Self-Consistency Checks of SM Post Higgs Discovery 2 Short Lifetime(~10-25 s) Decays before hadronization – Unique among the quarks! Access to Polarization and Spin Correlations 3 Processes including top are backgrounds for new physics + Exotics and SUSY Good Understanding ➙ Improvements in Searches 4 Hints of new BSM/physics? Exotic Particles Could Decay Preferentially to Top Quarks JOSE ENRIQUE GARCIA 13

WHAT CAN WE MEASURE? POLARIZATION CROSS-SECTION PDF SPIN, COUPLINGS MASS,… JOSE ENRIQUE GARCIA 14

TOP QUARK PRODUCTION Decay Modes single top : production via EW interaction top pair production Decay Modes JOSE ENRIQUE GARCIA 15

TOP QUARK PRODUCTION Most Common Experimental signatures Backgrounds top pairs : depending on the decay channel t-channel : 1 isolated leptons (e / μ), one b-tagged jet, 1 forward jet, missing ET Wt channel : 2 isolated leptons (e / μ), one b-tagged jet, missing ET s-channel : 1 isolated lepton (e / μ), two b-tagged jets, missing ET Backgrounds JOSE ENRIQUE GARCIA 16

INCLUSIVE TT CROSS-SECTION All channels measured ➞ no new physics Parallel session talk JOSE ENRIQUE GARCIA 17

INCLUSIVE TT CROSS-SECTION arXiv:1406.5375 arXiv:1312.7582 Selection : 2 opposite sign and flavor leptons, at least two jets and at least one b-tagged Simultaneous measurement of cross- section an b-jet efficiency Selection : 2 opposite sign leptons, at least two jets and at least one b-tagged. ETmiss > 40 GeV and Z mass veto. Cut and count to extract cross section Add somewhere that it is 8 TeV 4.3% 5.5% 5.7% JOSE ENRIQUE GARCIA 18

INCLUSIVE TT CROSS-SECTION Errors : ±5.7% (theo) vs ±3.5% (eμ) ➞ experiments challenge theory JOSE ENRIQUE GARCIA 19

TOP POLE MASS With cross-section tt+1jet : ATLAS-CONF-2014-053 With cross-section tt+1jet : arXiv:1406.5375 Check notes some alternative measurements (also showed in parallel sessions) Most precise measurement are not pole mass but MC mass… JOSE ENRIQUE GARCIA 20

TOP MASS JOSE ENRIQUE GARCIA 21

SINGLE TOP : T-CHANNEL Total cross-section measured with good precision. Additionally, fiducial cross-section measurement, within detector acceptance (ATLAS), is done which allow to have reduced uncertainties. Extraction of Vtb (σα |Vtb|2) and cross-section ratio (top/anti-top) sensitive to PDFs arXiv:1403.7366 ATLAS-CONF-2014-007 Results for 7 TeV : arXiv:1406.7844 (ATLAS) and arXiv:1209.4533 (CMS) JOSE ENRIQUE GARCIA 22

SINGLE TOP : WT PRODUCTION ATLAS-CONF-2013-100 arXiv:1401.2942 A Likelihood Fit performed on the Boosted Decision Tree output (BDT) over the eμ channel and one jet (one tag) and 2 jets (at least one tag) A Likelihood Fit performed on the BDT output over three channels (ee, μμ, eμ) and three jet selection configurations Sistemáticos? Significance = 4.2σ (observed) Significance = 6.1σ (observed) JOSE ENRIQUE GARCIA 23

SINGLE TOP : S-CHANNEL @ 8 TeV s-channel is the most difficult to detect in LHC due to the small cross-section, needs an annihilation quark (q) – antiquark (q’). BDT is used to improve discrimination signal to background: A binned maximum-likelihood fit is performed on the output of the BDT to extract the signal content Upper limit to the cross-section @ 95% CL : Significance = 1. 3σ (observed) Significance = 2.1σ (observed) arXiv:1410.0647 CMS-TOP-13-009 sistemáticos, información sobre el fondo. JOSE ENRIQUE GARCIA 24

SINGLE TOP CROSS-SECTIONS JOSE ENRIQUE GARCIA 25

TT+V (W/Z) SM : ATLAS-CONF-2012-126 arXiv:1406.7830 3 signatures : Same sign leptons (ttW), dilepton (ttW, ttZ), trilepton (ttW,ttZ). Multivariate analysis. Simultaneous maximum likelihood fit. 3 signatures : Same sign leptons (ttW), trilepton (ttZ), four-lepton (ttW,ttZ). Cut based analysis. Simultaneous maximum likelihood fit. Combined significance : 4.9σ Combined significance : 3.7σ SM : JOSE ENRIQUE GARCIA 26

SUMMARY ~5 orders of magnitude JOSE ENRIQUE GARCIA 27

SUMMARY Electroweak and top measurements are achieving high precision : Experimental systematics are at the level of theory uncertainty Measurements help to constrain : MC models, QCD calculations and PDFs Good understanding is fundamental as these processes are background to BSM searches and Higgs boson measurements. Measuring multi-bosons is a step towards the exploration of EWSB sector BSM. Vector boson scattering will be one of the keys in Run-2. Many interesting results had to be left out from this presentation… JOSE ENRIQUE GARCIA 28

LHC Data collected by experiments : 2011 – 5 fb-1 @ 7 TeV Peak Luminosity in Run 1 : 0.75 x 1034 cm-2 s-1 For the 8 TeV data the average pileup of <μ> = 21 For comparison, future runs : Expected for Run 2/3 : 1.5 to 2x1034 300 fb-1 till 2022 HL-LHC from 2025 : 5 x 1034, 3000 fb-1 JOSE ENRIQUE GARCIA 30

WW ATLAS-CONF-2014-033 Check conf JOSE ENRIQUE GARCIA 31

Electroweak and Top cross-sections JOSE ENRIQUE GARCIA 32

DIFFERENTIAL TTBAR CROSS-SECTION Selection : Lepton + jets Measured several normalized (unfolded) differential distributions : pTt, pTtt, mtt, ytt Reduced systematics Compared to a variety of event generators, parton showering models, and PDFs Alpgen (2 ⟶ nME@LO) describes best ytt distribution HERAPDF gives the best overall description of the data Other PDFs give fairly poor agreement ATLAS : arXiv:1407.0371 Add top pT plot or comment more, check CMS measurement JOSE ENRIQUE GARCIA 33

Cross section ratios JOSE ENRIQUE GARCIA 34

S-CHANNEL @ 8 TeV : SELECTION arXiv:1410.0647 Isolated high pT lepton missing energy (ETmiss) b-jet from top decay Second b-jet, recoil against top Cuts 1 muon or electron pT > 30 GeV 2 b-tagged jets additional cuts JOSE ENRIQUE GARCIA 35

T-CHANNEL @ 8 TeV : SELECTION ATLAS-CONF-2014-007 “light” jet with high pseudo-rapidity (η) Isolated high pT lepton missing energy (ETmiss) b-jet central with large momentum Second b-jet with lower pT Cuts 1 muon or electron pT > 25 GeV (|η|< 2.5 ) 2 jets 1 b-tagged pT > 30 (|η|< 4.5 ) / pT > 35 GeV ( 2.75 < |η|< 3.5 ) additional cuts ETmiss > 30 GeV, mTW > 50 GeV, JOSE ENRIQUE GARCIA 36

WT PRODUCTION @ 8 TeV : SELECTION ATLAS-CONF-2013-100 exactly 2 opposite charge and isolated leptons missing energy (ETmiss), 2 neutrinos 1 b-jet from top decay Cuts 2 leptons eμ pair, pTl > 25 GeV 1 or 2 jets, at least one b-tag pT > 30 GeV JOSE ENRIQUE GARCIA 37

SINGLE TOP : T-CHANNEL Neural Network used to discriminate background. Maximum Likelihood Fit to the output of the NN to obtain the contributions from the different processes. Sistemáticos? ATLAS-CONF-2014-007 arXiv:1403.7366 JOSE ENRIQUE GARCIA 38

BOOSTED DECISION TREE Recover events failing cuts in a cut based analysis. Using simulation for signal and background to compute purity. Resulting in a weight for each event. JOSE ENRIQUE GARCIA NAVARRO 39