Physics at LHC: Selected results from EW sector and news on Run II E. Richter-Was, Institute of Physics UJ Results from EW sector: Higgs Boson couplings (ATLAS & CMS combination) Standard Model precision measurements News on Run II E. Richter-Was, seminarium IFT UW 13.10.2014

E. Richter-Was, seminarium IFT UW LHC physics 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs boson in Standard Model Run I of LHC was the run of the Higgs Boson Rapid transition from searches over discovery to measurement 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs boson measurements Typically divided into Coupling measurements: measure event counts in various phase-space regions, naturally emerges from searches Properties measurements: measure quantum numbers and other properties using dedicated analyses 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW Mass of Higgs boson Measured with < 0.2% precision (ATLAS+CMS) 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs boson: spin-0 particle, compatible with CP-even Angular analysis of CMS and ATLAS Run I data rules out spin 2 at 99.9% C. L. 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs boson couplings (ATLAS-CONF-2015-044, CMS-PAS-HIG-15-002) Reach experimental area of Higgs properties: the Higgs couplings strength to other SM particles, e.g. All coupling strengths predicted by SM, given known Higgs boson mass Accessible in various combinations and admixtures, large variety of ATLAS & CMS observed Higgs boson decay rates. Powerful test of nature of Higgs boson: SM or subtly different? 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs bosons – alternatives to the SM Higgs boson What else could the 125 GeV state be? Many alternative theories exist, for example Light CP-even h(125) of a Two Higgs double Model (h, H, H+-, A) Pseudo NG boson from high energy theory (Composite Higgs) In either case, couplings of BSM h(125) candidate (slightly) different from SM Higgs boson Goal here is not to pick a specific model – but to develop a generic framework to quantify possible deviations in Higgs couplings from SM 13.10.2014 E. Richter-Was, seminarium IFT UW

Standard Model Higgs boson decays The natural width of the Higgs boson is expected to be very small (<< resolution) 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs boson production in the SM 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs boson production in the SM 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs boson production in the SM Very small SM cross-section due to almost completely destructive interference. For opposite sign W/t Higgs couplings , s(tHqb) increases by factor 13 and s(WtH) by factor 6. 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs boson production in the SM Diagram similar to ttH, but experimentally not really distinguishable from ggF and 100x smaller in SM 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs production and decay – input measurements 13.10.2014 E. Richter-Was, seminarium IFT UW

Signal strength measurements by ATLAS and CMS Each experiment has O(15) signal strength measurements focusing on the variety of production and decay models. 13.10.2014 E. Richter-Was, seminarium IFT UW

Signal strength fits of individual measurements 13.10.2014 E. Richter-Was, seminarium IFT UW

Understanding signal strength Signal strength m is observed rates normalised to SM predictions Disentangling production (mi) and decay (uf) always requires assumption of narrow Higgs width Additional assumptions required when combining measurements 13.10.2014 E. Richter-Was, seminarium IFT UW

Beyond signal strength – the k framework Alternatively one can disentangle deviations in production and decay with explicit modeling of Higgs width Introduce functions ki to describe deviations from SM 13.10.2014 E. Richter-Was, seminarium IFT UW

Beyond signal strength – the k framework Parameters kj correspond to LO degrees of freedom 13.10.2014 E. Richter-Was, seminarium IFT UW

The k framework - the total width Note that total H width scales all observed cross-sections Since GH is not yet directly measured with a meaningful precision, must make assumption on GH to interpret cross-sections in terms of Higgs couplings. Eg. in absence of BSM H decays (invisible, undetected, etc.) can assume SM width, adjusted by effect of k-rescaled couplings. 13.10.2014 E. Richter-Was, seminarium IFT UW

The k framework - the dictionary 13.10.2014 E. Richter-Was, seminarium IFT UW

The k framework - the dictionary 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW Single measurement Every measurement consists of one or more signal regions designed to select target Higgs production/decay Distribution of a (multivariate) discriminant is interpreted in terms of sum of signal and background contributions. 13.10.2014 E. Richter-Was, seminarium IFT UW

Profile likelihood formalism for (systematic) uncertainties Build likelihood function for each signal, control region of the data. 13.10.2014 E. Richter-Was, seminarium IFT UW

Profile likelihood formalism for (systematic) uncertainties Build likelihood function for each signal, control region of the data. 13.10.2014 E. Richter-Was, seminarium IFT UW

Decomposition of signal contributions in channel Channels selections hardly ever 100% pure in production process (especially ‚untagged’) -> separately model distributions from all contributing Higgs production processes. Channels selections hardly ever 100% pure in decay mode (eg. H->WW selection has contribution of H->tt decays) -> Interpret such contributions as Higgs signal (of appropriate type) in coupling analysis. 13.10.2014 E. Richter-Was, seminarium IFT UW

Measurements of backgrounds often data-driven using control regions 13.10.2014 E. Richter-Was, seminarium IFT UW

Distributions: subject to systematic uncertainties Expected distributions mostly derived from simulation chain. 13.10.2014 E. Richter-Was, seminarium IFT UW

Profiled likelihood formalism for (systematic) uncertainties Extended description of each signal/background distribution so that it can describe distribution under a wide range of parameters for which the true values are unknown (energy scales, QCD scales…) 13.10.2014 E. Richter-Was, seminarium IFT UW

Profiled likelihood formalism for (systematic) uncertainties Correlate parameters as needed between channels, experiments 13.10.2014 E. Richter-Was, seminarium IFT UW

Correlated uncertainties in ATLAS/CMS combination Full combination describes ~580 signal regions & control regions from both experiments. Grand total of ~4200 nuisance parameters, related to (systematic) uncertainties. Correlation strategy of nuisance parameters a delicate and complicated task: Detector systematic uncertainties: generally correlated within, not between experiments Signal theory uncertainties (QCD scales, PDF, UEPS) on inclusive cross-sections: generally correlated between experiments Signal theory uncertainties on acceptance and selection efficiency: uncorrelated between experiments PDF uncertainties on signal cross-sections: uncorrelated between experiments 13.10.2014 E. Richter-Was, seminarium IFT UW

Signal strength fits of individual measurements 13.10.2014 E. Richter-Was, seminarium IFT UW

The global signal strength Assuming SM ratios of production cross-sections and decay rates 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs signal strength by production and decay mode 13.10.2014 E. Richter-Was, seminarium IFT UW

Signal strength in V, F – mediated production by decay Measure ggF+ttH production „fermion mediated” and VBF+VH production „boson mediated” for each decay mode 13.10.2014 E. Richter-Was, seminarium IFT UW

Constraints for Higgs couplings to fermions, bosons Assume universal scaling parameters for Higgs couplings to fermions (kF), bosons (kV), resolved loops, only SM physics in loops, no invisible Higgs decays, kF,V ≥ 0) 13.10.2014 E. Richter-Was, seminarium IFT UW

Constraints for Higgs couplings to fermions, bosons Expanding parameter range to include negative couplings 13.10.2014 E. Richter-Was, seminarium IFT UW

Constraints on tree-level Higgs couplings Assume only SM physics in loops, no visible Higgs decays Fit for scaling parameters for Higgs couplings to W, Z, b, t, t, m NB: low measured value of kb reduces total width GH => all ki measured low [w.r.t m=1.09] 13.10.2014 E. Richter-Was, seminarium IFT UW

Constraints on tree-level Higgs couplings 13.10.2014 E. Richter-Was, seminarium IFT UW

Allowing for BSM contributions in Higgs coupling interpretations Results shown so far assumed no invisible (BSM) Higgs decays nor BSM contributions to loops. Now drop these assumptions. Represent loop processes (ggF, H->Z/gg) with effective parameters (kg,kg), rather than assuming SM content 2. Allowing BSM Higgs decays (invisible, undetected etc…) to increase the total width 13.10.2014 E. Richter-Was, seminarium IFT UW

Limit on invisible Higgs decays from Higgs couplings Concept: set limit on BR to (invisible, undetected) Higgs decays Scenario 1: - Assume 6 tree-level couplings at SM (k=1) but 2 effective loop couplings floating Scenario 2: - Keep all 6+2 coupling parameters floating, but bound vector boson couplings kW,kZ ≤ 1 13.10.2014 E. Richter-Was, seminarium IFT UW

Focus on effective couplings for loop processes Fix all tree-level Higgs couplings to SM (kW,kZ,kb,kt,km,kt=1) and BRinv = 0 13.10.2014 E. Richter-Was, seminarium IFT UW

Constraints on Higgs couplings allowing BSM physics in loops & decays 13.10.2014 E. Richter-Was, seminarium IFT UW

Generic parametrizations Goal of (most) generic parametrizations is to provide summary of Higgs coupling while make minimal number of assumptions and with minimal exposure to theory uncertainties Most generic model is signal strength model with ratios. Choose ggF H->ZZ as reference channel since it is the cleanest channel and has the smallest systematic uncertainty. Ratios of cross-sections and BRs reduce exposure to dominant theoretical uncertainties on inclusive cross-sections 13.10.2014 E. Richter-Was, seminarium IFT UW

Signal strength models with ratios 13.10.2014 E. Richter-Was, seminarium IFT UW

Alternatively, measure ratio of couplings strengths No assumption on Higgs total width needed, as GH cancels in all expressions. 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW Summary ATLAS and CMS Higgs boson coupling results have been combined, sensitivity on signal strength improved by almost sqrt(2) Higgs to tt and VBF production established at more than 5s level The most precise results on Higgs production and decay and constraints on its couplings have been obtained at O(10%) precision. Different parametrisations have been studied, all consistent with the SM predictions within uncertainties SM p-value of all combined fits in range of 10%-88% 13.10.2014 E. Richter-Was, seminarium IFT UW

Run I electro-weak measurements 13.10.2014 E. Richter-Was, seminarium IFT UW

Electroweak measurements at LHC EWK production Three-boson VVV Di-boson VV 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW VBS ssWW production First evidence for Vector-Boson-Scattering based on use of same-sign WW final state Essential to experimentally probe the nature of the EWSB, flagship analysis for Run 2 and beyond! In Run 1 both ATLAS and CMS has sensitivity for first evidence Observed (Expected) significance: ATLAS 3.6s (2.8s) , CMS 1.9s (2.9s) Experimental signatures: Dilepton +MET + 2 jets Combination of „EWK” and „QCD” (O(as2aEW4)) 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW VBS ssWW production 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW VBS ssWW: aQGC limits 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW Data with Run II 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW 13.10.2014 E. Richter-Was, seminarium IFT UW

E. Richter-Was, seminarium IFT UW BACKUP 13.10.2014 E. Richter-Was, seminarium IFT UW

Focus on up/down-type fermion and lepton/quark asymmetries Several BSM physics models (notably 2HDM), predicts asymmetries in couplings between up-type and down-type fermion couplings, and between lepton and quarks couplings Since goal is to measure asymmetry, directly parametrize model in terms of rations and coupling strength modifiers. Assume no BSM physics in loop processes. No assumption on invisible decays needed, since no assumption on GH needed (total width cancels in ratio of couplings) 13.10.2014 E. Richter-Was, seminarium IFT UW

Focus on up/down-type fermion and lepton/quark asymmetries Several BSM physics models (notably 2HDM), predicts asymmetries in couplings between up-type and down-type fermion couplings, and between lepton and quarks couplings 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs coupling model with ratios 13.10.2014 E. Richter-Was, seminarium IFT UW

Higgs coupling model with ratios 13.10.2014 E. Richter-Was, seminarium IFT UW

Statistical treatment - profile likelihood From L(ATLAS+CMS) construct the profile likelihood for a statement on the parameter(s) of interest a 68% confidence interval defined by z rise of 1 unit in L(a) (asymptotic limit) 13.10.2014 E. Richter-Was, seminarium IFT UW

Specific model II: resolved loops, no BSM 13.10.2014 E. Richter-Was, seminarium IFT UW

Electroweak measurements at LHC Electroweak sector of the SM based on SU(2)xU(1) gauge group, that is non-Abelian -> Triple and quartic gauge couplings Measurements: VBF/VBS: observation and evidence Di-boson and three-boson measurements Measurements require complex analyses (syst. limited) Run 1 more to offer before Run 2 takes over Challenges also for theorists, clearly need for precise predictions 13.10.2014 E. Richter-Was, seminarium IFT UW