First Year of Electroweak Physics in CMS CMS-Physics France, April 1 st 2010

CMS Physics France, 1 st April 2010 Electroweak Group Organization n Goal : publish results of highest quality u rule: go for significant, lasting results n Organization u for each paper, appoint a pair of editors u in house “experts” l MC generators, DQM, luminosity, datasets, triggers, etc. n First deliverable: W & Z production cross-section u only exception to the rule: we need to publish fast! u a second paper will follow l before the end of the year l will serve as a reference for EWK analyses with leptons n The Vector-Boson task Force (VTBF) u driving force behind both W & Z Production X-Section papers u establish the basics of EWK analyses u implement full vertical integration with POGs (and DPGs) l including: Muon, E/gamma, JetMET, Tracking, Particle-Flow 2

CMS Physics France, 1 st April 2010 Survey of Electroweak Activities 3 Institutions with interest in first year EWK physics Tentative list of EWK papers The collaboration was invited to specify their interests and commitments to one or more of the designated papers

CMS Physics France, 1 st April 2010 Task Forces 4 EWK PAG conveners VBTF: W/Z papers VBTF: W/Z papers V + Jets Z to   (WW) V  Giuseppe Bagliesi Monica Vazquez Vitaliano Ciulli Ilaria Segoni Vuko Brigljevic Yurii Maravin Dmytro Kovalskyi Guillelmo Gomez Michael Schmitt Gautier H de M

CMS Physics France, 1 st April 2010 W & Z Analyses: Plans for ICHEP pb  1 pb  twice: 3800 Ws and 350 Zs Measurement of W & Z cross sections W + /W - cross section ratio Z/W cross section ratio q T distribution for Z Z rapidity distribution W charge asymmetry W polarization … twice: 380 Ws and 35 Zs show clear & clean W and Z signals 1 st measurement of W cross section (~ 10% error) displays of W, Z, W/Z+jet events, … two leptonic channels together

6 VBTF muon reconstruction and selection muon reconstruction and selection electron reconstruction and selection electron reconstruction and selection MET QCD background estimation QCD background estimation trigger efficiency trigger efficiency lepton reconstruction efficiency lepton reconstruction efficiency calibration assessment calibration assessment event selection event selection acceptance calculation acceptance calculation cross section and plots cross section and plots There are about 10 elements of this analysis – 10 teams Complete list of tasks at: There are obvious interconnections among the teams

CMS Physics France, 1 st April 2010 Constraining the Parton Densities 7 H1 & ZEUS  ( pp → V + X 7TeV ~ 70% of  ( pp → V + X 10 TeV

CMS Physics France, 1 st April 2010 W Analysis 8 Tight lepton selection Signal versus backgrounds in MET or MT distributions Preselection: GsfElectron with E T >30 GeV ECAL fiducial region ( |  | < 2.5 ) match HLT primitive Selection: identification ( , ,  i  i , H/E) isolation (ECAL, HCAL, tracker) veto additional electron with E T >20GeV Electron channel Muon channel Selection Good quality muon pT > 25 GeV, |  | < 2 track isolation veto additional muon EWK EWK typical cuts MET > 30 GeV M T > 40 GeV

CMS Physics France, 1 st April 2010 W Analysis, QCD Backgrounds 9 isolation variable W charge asymmetry analysis (muons) Hadronic (QCD) W background dominated by jets mis-identified as leptons Missing ET comes from jet energy mis-measurements Simulation cannot be trusted: use “data-driven” methods General idea of data-driven methods produce signal free control samples by inverting selection cut(s) “ABCD” method A B D C the fractions of signal and EWK backgrounds are known in regions A, B, C and D signal: using MC and data EWK background: using MC the fractions of QCD background in regions A and B are determined under the assumption QCD A /QCD B = QCD D /QCD C (to be checked on MC) signal QCD Muon channel

CMS Physics France, 1 st April 2010 W Analysis, QCD Background 10 Pseudo-experiment 1 pb -1 at 7 TeV Particle-Flow MET Preselection Point 80% efficiency Selection: VBTF Electron channel Determine background shape from the data tight anti-selection cuts signal-free control sample Choose anti-selection variable(s) with less impact on MET shape Isolation variables affect the MET shape too much Identification variables  and  (keep ~10% signal) “Template” method

CMS Physics France, 1 st April 2010 Signal “Template” from Z Events 11 Basic idea: “Emulate” missing ET distribution for W events using Z events ECAL barrel CaloMET Blue: “true” MET Red: “emulated” MET EWK AN Muon channel Electron channel impose W selection cuts to one lepton emulate neutrino by excluding the second lepton contribution from the event account for known difference in lepton spectra for a given q T (scaling function of M W /M Z ) account for different W/Z kinematics and lepton/neutrino acceptance using simulation (second order effects) compute the transverse missing energy

CMS Physics France, 1 st April 2010 Extracting Signal Yields pb -1 using MC template for signal using template from Z events for signal AN VBTF 1 pb -1 Muon channel Electron channel

CMS Physics France, 1 st April 2010 Z Analysis 13 EWK EWK Selection: GsfElectron with E T >20 GeV ECAL fiducial region ( |  | < 2.5 ) 60 < M ee < 120 GeV Selection: Good quality muon pT > 20 GeV, |  | < 2 60 < M  < 120 GeV Muon channel Electron channel Sample used for Tag & Probe Determination of lepton efficiencies (trigger, identification, isolation, etc.)

CMS Physics France, 1 st April 2010 W & Z, Typical Uncertainties 14 predicted W & Z results for ∫ L dt = 10 pb -1 at √s = 10 TeV evolution of Z statistical error at √s = 10 TeV theory errors ~ 1% PDF uncertainties luminosity Muon channel Electron channel EWK AN ratios and asymmetries (cancellation of uncertainties) differential x-sections

CMS Physics France, 1 st April 2010 W Lepton Charge Asymmetry 15 EWK pb -1 Muon channel 100 pb -1 W + W -- charge asymmetry CMS can start constraining parton densities with relatively modest samples

CMS Physics France, 1 st April 2010 Differential Z Cross-Sections 16 corrected Z rapidity distribution EWK Z rapidity distributions Electron channel importance of including forward electrons: electron reconstruction in HF PDF uncertainty is small in this case

CMS Physics France, 1 st April 2010 Z Differential Cross-Sections 17 Transition soft /perturbative QCD ~30 GeV Z transverse momentum (q T ) spectrum K. Kotov, thesis Muon channel Importance of defining the right observables for theoretical interpretation & tunings and meaningful comparisons with other experiments

CMS Physics France, 1 st April 2010 V+jets: Probing QCD at N(N)LO 18 Short term plan, O(50 pb -1 ): rate of jet production in association with a weak boson inclusive jet counting exclusive jet counting, unfolding comparison of rates in association with W and Z CMS: use different jet reconstruction CaloJets (raw/corrected), TrackerJets, PFJets probing different regions of phase space Longer term plan, O(1 fb -1 ) characterize V+jets in detail event shapes study of rapidity gaps etc.

CMS Physics France, 1 st April 2010 W+jets: Choice of MET 19 Type-I corrected MET Particle Flow MET AN Muon channel >= 0-Jet>= 1-Jet>= 2-Jets

CMS Physics France, 1 st April 2010 W/Z+Jets: Tests of QCD Scaling 20 “Z-Candle” Analysis W/Z+Jets, test of Berends-Giele Scaling Example: electrons + TrackerJets data-driven SM backgrounds to Higgs and SUSY signals

CMS Physics France, 1 st April 2010 W Polarization Asymmetry 21 High p T W recoiling against jet(s) large Q 2 : one valence quark involved in general at LHC qluons preferred over sea anti-quarks depends on pT and rapidity of the V+jet system quark-gluon initial state u + g → W + + d u and d quarks are left-handed the W + tends to be left-handed d + g → W - + u identical spin configuration the W - tends to be left-hand softer charged antileptons for W + harder charged leptons for W - antiquark-gluon initial state opposite as above (no net polarization effect at the Tevatron) quark-antiquark final state no left/right spin preference for Ws ∫ L dt = 10 pb -1 at √s = 7 TeV polarization effects can be observed early Markus Stoye et al. (IC)

CMS Physics France, 1 st April 2010 WW Observation 22 muon-muon, electron-electron & electron-muon channels EWK ∫ L dt = 100 pb -1 at √s = 10 TeV reduction of DY background reduction of top background Joined paper with HIGGS triple gauge couplings irreducible to H → WW

CMS Physics France, 1 st April 2010 WW: Data-Driven Methods 23 EWK Estimation of top background from soft muon rate at large jet multiplicity Estimation of contribution of main backgrounds:to WW top Drell-Yan W+jets W+jets background using “fakable” lepton in QCD enriched sample W+jets background using sidebands of isolation distribution

CMS Physics France, 1 st April 2010 Establishing First Z/W →  Signals Establishing First Z/W →  Signals 24 “Templates” from: Signal: Z to mu-mu with taus from MC Backgrounds: inverted selections Letizia Lusito thesis Z →  W →W →

CMS Physics France, 1 st April 2010 Summary n A rich program of Electroweak physics with CMS data n Measurements of W and Z production cross section at 7 TeV u as in many EWK precision measurements have PDF as the main source of uncertainty u luminosity measurements are crucial, too n Differential cross-section measurements and asymmetries u tell us more than total cross-section measurements n Well-understood W and Z dynamics u paves the way for Higgs physics and SUSY and BSM searches u as well as longer term EWK precision measurements n Longer term, other topics u diboson production and study of triple gauge couplings l sensitivity on New Physics in the gauge sector of EWK theory u measurement of the W mass and width l the goal is to reach the 20 MeV uncertainty on the mass 25

CMS Physics France, 1 st April 2010 Other, Longer Term Topics The W mass m W is an important electroweak parameter, linked to G F,  and m Z with Measurements on m W and M top are used to constrain the mass of the Higgs boson Precision measurements of electroweak corrections is a way to probe particles at much higher energy scale