PASCOS 2013 November, 2013

Transcription

1 Combined measurements of the Mass and Couplings Properties of the iggs boson & Di erential cross sections of the iggs boson measured in the diphoton decay channel using the Detector Florian U. Bernlochner on behalf of the Collaboration University of Victoria, Canada PASCOS November, /8

2 Talk Overview i. iggs Boson Production and decay ii. The detector and the LC iii. Combining Mass measurements from! &! ZZ iv. Combining Coupling measurements for all search channels v. Di erential Cross sections from! vi. Summary & Conclusions [-CONF--] [-CONF--] [Phys. Lett. B 7 () 88] [-CONF--7] /8

3 i.a iggs Boson Production Existence of iggs field essential for mass generation of Weak vector bosons + quarks & leptons in Standard Model # Spontaneous symmetry breaking in iggs Mechanism produces new scalar particle: the iggs boson u u d In pp collisions iggs Boson produces via gg!, VBF, Z, W & tt Cross section for various m at p s =8TeV: σ(pp +X) [pb] pp (NNLO+NNLL QCD + NLO EW) pp qq (NNLO QCD + NLO EW) pp W (NNLO QCD + NLO EW) pp Z (NNLO QCD +NLO EW) u u d s= 8 TeV LC IGGS XS WG iggs Production g t g q q V q q q V V q pp tt (NLO QCD) - 8 M [GeV] /8

4 iggs Boson decays after Branching fractions for iggs decay: iggs BR + Total Uncert [%] cc bb gg Z WW 8 8 M [GeV] ZZ i.b iggs Boson Decay & Discovery ps into other SM particles LC IGGS XS WG Search Channels *! b b for V *! + *! + *! *! Z *! WW ( ) *! ZZ ( ) Last year, th of July and CMS announced discovery of new boson # Couplings and spin (see talk of Roberto Di Nardo) seem compatible with SM iggs boson /8

5 ii. Detector & Large adron Collider is multipurpose detector focus: iggs, EW, BSM, B physics Multilayered EM & adronic calorimeter excellent Tracking & Muon detection Very successful & run: Total Integrated Luminosity fb Preliminary LC Delivered Recorded Good for Physics, Delivered: 5. s = 7 TeV fb Recorded: 5.8 fb Physics:.57 fb, Delivered:.8 s = 8 TeV fb Recorded:. fb Physics:. fb Jan Apr Jul Oct Jan Apr Jul Oct Month in Year.9/fb integrated luminosity good for physics detector & arial picture of the LC 5/8

6 iii.a Combining Mass measurements of! ± &! ZZ Two measurements w/ good mass resolution:! &! ZZ! `!! ZZ! ` iggs Mass [GeV].8 ±. ± Events/5 GeV 5 5 Data + SM iggs Boson m =. GeV (fit) Background Z, ZZ* Background Z+jets, tt Syst.Unc. ZZ* l s = 7 TeV Ldt =. fb s = 8 TeV Ldt =.7 fb First error is statistical, second systematic. 5 Can combine both measurements under the assumption of a single resonance: [GeV] m l Profile likelihood for combination # (m )= L(m ) L(bm ) Events / GeV 8 s = 7 TeV Ldt =.8 fb s = 8 TeV Ldt =.7 fb Data + SM iggs boson m =.8 GeV (fit) Bkg (th order polynomial) γ γ with the full likelihood contours from the individual measurements in m &, takinginto account correlated systematics. Events - Fitted bkg 5-5 m γ γ [GeV] Diphoton and ` mass spectra Figure : Invariant mass distribution of diphoton candidates after /8 all

7 iii.b Combining Mass measurements from! &! ZZ Combined mass maximizing test statstics: m =5.5 ± GeV -lnλ 7 5 Preliminary s = 7 TeV: Ldt =.-.8 fb s = 8 TeV: Ldt =.7 fb Combined (stat+sys) Combined (stat only) γ γ (*) ZZ l σ To test the consistency between both measurements a modified test statistic can be used. # m = m m ` m = ±. GeV Compatibility with m of the level of.5% (. ), tension between both measurements Assuming non-gaussian uncertainties for the principal systematic uncertainties (Z! ee calibration/extrapolation, material upstream & energy scale of presampler detector) improvescompatibilityto8%. -lnλ σ m [GeV] Preliminary s = 7 TeV: Ldt =.-.8 fb s = 8 TeV: Ldt =.7 fb σ 8 -lnλ() σ σ 5 m γ γ -m [GeV] l 7/8

8 Table 9: For the WW analysis of the 8 TeV data, the numbers of events observed in the data and expected from signal (m = 5.5 GeV) and backgrounds inside the transverse mass regions.75m < mt < m for Njet andmt <.m for Njet. All lepton flavours are combined. The total background as well asits main components are shown. The quoted uncertainties includethestatistical and systematic contributions, and account for anticorrelations between the background predictions. Signal strength combination from!,! ZZ! `,! WW!` ` Njet = Njet = Njet Observed # Signal ± ±.9 ±. Can combine both Total background measurements 79 ± 9 ± 8under ± the WW 55 ± 8 ±. ±.5 assumption of a single resonance: Other VV 58 ± 8 7±.9±. Top-quark 9 ± 5 95± 8 5. ±. Z+jets ± ± ± W+jets ± ± 5.7±. Profile likelihood for combination # those used to normalise the backgrounds, illustrates the quality of the background estimates. The expected numbers of signal () = L() and background events at 8 TeV are presented in Table 9. The VBF process contributes %, % and8% L(b) ofthe predictedsignal in the Njet =, =, and finalstates,respectively. Coupling strength = measured / SM Thetotalnumberof observed events in the same mt windows as in Table 9 is 8 in the 7 TeV data and 95 in the 8 TeV data. An excess of events relative to the background-only expectation is observed in the data, with the maximum deviation!! ZZ (. )occuringatm =! `! WW GeV. For! ` ` m = 5.5GeV, a significance of.8 is observed,. ±. compared. ±. with an expected value. of ±.8.for a SM iggs boson. Additional interpretation of these results is presented Evaluated at m =5.5inGeV Section 7. Transverse mass m T = iv.a Combining Coupling measurements Events Events / GeV / GeV Data - Data Bkg. - Bkg. 8 s = 7 TeV Ldt =. fb 7 8 s = 8 TeV Ldt =.7 fb s = 7 TeV Ldt =. fb 7 WW* lνlν + / jets s = 8 TeV Ldt =.7 fb 5 WW* lνlν + / jets 5 SM Data iggs + boson Total m sig.+bkg. = 5 GeV WW SM iggs boson = 5 GeV 8 8 Bkg. subtracted data 8 SM iggs boson m = 5 GeV 8 Bkg. subtracted data SM iggs boson m = 5 GeV m T [GeV] 8 (a) 8 m T [GeV] m Other WW VV Single tt Top W+jets Other VV Z/γ* Single Top iggs boson property measurements m T [GeV] The E results from the individual channels described in T `` + E miss / T p`` T + Emiss T distributions for! WW(b)!` ` m T [GeV] the previoussections are combinedhere to extractinfor- Events Events / / GeV GeV s = 7 TeV Ldt =. fb s = 8 TeV Ldt =.7 fb s = 7 TeV Ldt =. fb WW* eνν + j s = 8 TeV Ldt =.7 fb 8 WW* eνν + j 8 Data + Total sig.+bkg. tt W+jets Z/γ* Data + Total sig.+bkg. VBF Data m+ = 5 GeV ggf Total msig.+bkg. = 5 GeV VBF m = 5 GeV tt ggf m = 5 GeV WW Z/γ* tt Other WW VV Z/γ* Single Top W+jets Other VV Single Top W+jets 8/8

9 iv.b Combining Coupling measurements Combined signal strength results for and VBF+V / ggf+tt : m = 5.5 GeV γ γ +. = s = 7 TeV Ldt =.-.8 fb s = 8 TeV Ldt =.7 fb ±. ±.5 ± Low p =. Tt -. ±. +.7 igh p =.7 Tt -. ±.5 jet high +.8 =.9 mass (VBF) -. ±. +. V categories =.. ±.9 ZZ* l VBF+V-like categories Other categories +. = = =.5 -. WW* lνlν +. = ±. ±.7 ± ±.5 ±. ±. ± jet =.8 -. ±. +.7 jet VBF =. -. ±.5 Comb. γ γ, ZZ*, WW* +. =. -.8 ±. ±.5 ±. σ(stat) σ(sys) σ(theo) Total uncertainty ± σ on Signal strength () m = 5.5 GeV γ γ +.9 VBF+V =. ggf+tt -.5 s = 7 TeV Ldt =.-.8 fb s = 8 TeV Ldt =.7 fb ZZ* l +. VBF+V = ggf+tt WW* lνlν +. VBF+V =. ggf+tt. Combined γ γ, ZZ*, WW* +.7 VBF+V =. ggf+tt σ(stat) σ(sys) σ(theo) Total uncertainty ± σ ± σ 5 / VBF+V σ σ σ σ σ σ ggf+tt Overall signal production strength: =. +. Evidence for VBF+V: VBF+V / ggf+tt =. +.7 Figure 8: Measurements of the VBF+V/ggF+tt ratios for diboson final states and their combination, for a iggs boson mass m.8 =5.5 GeV. The best-fit values are represented by the solid vertical lines, with the total ± and ± uncertainties indicated by the darkand light-shaded band, respectively, and the statistical uncertainties by the.5 superimposed horizontal error bars. The numbers in the second column specify the contributions of the statistical uncertainty (top), 9/8

10 iv.c Combining Coupling measurements VBF+V s = 7 TeV s = 8 TeV 8 Ldt =.-.8 fb Ldt =.7 fb γγ ZZ* l WW* lν lν Standard Model Best fit 8% CL 95% CL - ln Λ B/BSM Projection in VBF+V -ggf+tt plane: γγ ggf+tt B/BSM σ SM expected -. σ +.9 =. Combined γ γ, ZZ*, WW* ZZ* l -.5 VBF+V ggf+tt Total uncertainty ± σ ± σ m = 5.5 GeV VBF+V ggf+tt 8 m = 5.5 GeV - σ(sys) σ(stat) m = 5.5s =GeV 7 TeV Ldt =.-.8 fb σ(theo) s = 8 TeV Ldt =.7 fb = WW* lνlν / VBF σ ggf+tt Fig -.7 Coupling ratio for for VBF. VBF+V VBF / ggf+tt Figure 7: Likelihood contours the production, ZZ only: 9:. for the combifigure Likelihood curve for the= ratio VBF. /ggf+tt +. tor ggf+tt = and WW channels in the (ggf+tt B/BSM, VBF+V nation of the, ZZ -.and WW chan σble!sm Evidence at. B/B ) plane for a iggs boson for massvbf m = production! 5.5 GeV. nels The and a iggs boson mass m = 5.5 GeV. The parameter com +. branching-ratio scale factors B/BSM can a priori be different for the/ggf+tt iscombined V profiled in the fit. The -.dashed curve shows the SM bes different final states. The sharp lower edge of the ZZ expectation. con γ γ, ZZ*, dashed WW* lines The horizontal indicate the 8% and 95% +. σ tours is due to the small number of events in this channel andcl. the VBF+V requirement of a positive pdf. The best fits to the data ( ) and the ggf+tt = σ 8% (full) and 95% (dashed) CL contours are indicated, as well as the SM expectation (+). 5 s = 7 TeV Ldt =.-.8 fb / 8 m

11 iv.d Combining Coupling measurements More detailed study on the iggs coupling can be done via leading order tree-level motivated framework. Assumptions: i. Single resonance at m =5.5 GeV ii. Narrow width approximation holds, i.e. rates of the process i!! f are given by B= i f with the iggs width, and f the partial width of the! f transition, and i the cross section for i! production. iii. No modifications in the tensor structure of the SM Lagrangian, i.e. iggs is + Free parameters in the framework: coupling scale factors apple j SM cross section times partial decay width, apple the total iggs width, or double ratios of the coupling scale factors ij = apple i /apple j. E.g. the e ective couplings of gg!! ( B) meas = apple g apple ( B) SM apple can be written as ratio of measured over / 8

12 Table : Summary of the coupling benchmark models discussed in this paper, where i j = i / j, ii = i i /, and the functional dependence iv.e Combining Coupling measurements assumptions are: V = W = Z, F = t = b = (and similarly for the other fermions), g = g ( b, t ), = ( b, t,, W ), and = ( i ). The tick marks indicate which assumptions are made in each case. The last column shows, as an example, the relative couplings involved in the of benchmark models with focus on di erent observables: ggvariety process, see Eq. (7), and their functional dependence in the various benchmark models. Model 5 Probed couplings Couplings to fermions and bosons Parameters of interest V, F FV, VV WZ, FZ, ZZ WZ, FZ, Z, ZZ g, Custodial symmetry Vertex loops Functional assumptions V = F g - - = Example: gg - ( F, V )/ ( F, V ) ( FV, FV, FV, ) FZ ( FZ, FZ, FZ, WZ ) ZZ FZ Z / ( g, ) g VV ZZ F FV The ticks correspond to a certain fixed functional dependence more details in backup - ln Λ other parameters, FZ and ZZ, are profiled. The three(benchmark model in Table ), which still provides Model : One coupling factors foryukawa fermions and dimensional compatibility of the SM prediction with the useful information on the relationship between best-fit value is 9%. and gauge couplings. Fits to for the data give the following one coupling factor bosons: F, V 8% CL intervals for FV and VV = V =V.-.8 / fb (when s = 7 TeV Ldt 8 TeV Ldt =.7 fb profiling over otherparameter): Model :theremoving thes =constraint on the iggs that them measured = 5.5 GeV (i.e. partial widths have to saturate the total width) only [.7,.] FV andvv VV =[., V / can.5] 8 - ln Λ(λ boson width WZ ) the rato FV() = F / V be measured.() Combined γ γ, ZZ*, WW* SM expected Model Model The two-dimensional compatibility of the SM pre+. F =.8.5[.7,.] FV.5 diction with the best-fit +.7 value is %. These results.5 V =. [.,.5] VBF. also exclude vanishing couplings of VV the iggs boson to/ ggf+tt fermions (indirectly, of mainly through the ggmodel procompatibility SM with both fits: %. Figure 9: Likelihood curve for the ratio VBF /ggf+tt for the combiduction loop) bynation more of than the 5., ZZ and WW channels and a iggs boson mass m = 5.5 GeV. The parameter s = 7 TeV Ldt =.-.8 fb s = 8 TeV Ldt =.7 fb [λ WZ,λ FZ,κ ZZ] Combined γ γ, ZZ*, WW* SM expected 5 Figure : Likelihood contours (8% CL) of the coupling scale fac tors model in TaV for fermions.f and..8 and bosons. (benchmark.. ble ), as obtained from fits to the three individual channels and their λ WZ / 8 combination (for the latter, the 95% CL contour is also shown). The

13 SM custodial symmetry: W & Z couple identically to iggs,i.e. WZ = apple W /apple Z = Model & :! VV & i!! VV information; Model also includes one degree of freedom for a potential BSM to! Model Model WZ = WZ =.8 ±.5 Compatibility of SM with Model : %. Calculated using full D covariance between determined values. Model 5: Result for apple g & apple : apple g =. ±. apple =. ±.5 Compatibility of SM with fit: %. Calculated using full D covariance between determined values. iv.f Combining Coupling measurements κ g ) WZ - ln Λ(λ s = 7 TeV Ldt =.-.8 fb s = 8 TeV Ldt =.7 fb [λ WZ,λ FZ,κ ZZ ] Combined γ γ, ZZ*, WW* SM expected SM s = 7 TeV Ldt =.-.8 fb Best fit s = 8 TeV Ldt =.7 fb 8% CL.8 95% CL Combined γ γ, ZZ*, WW*. λ WZ κ γ / 8

14 v.a Di erential Cross sections from! Di erential cross section measurements from! Analysis Idea Illustrated Unfolding Events / GeV Data-Bkg Simultaneous unbinned Likelihood fit in m Data Sig+Bkg Fit Bkg N events Ratio to POWEG Preliminary Preliminary pp γγ, s = 8 TeV L dt =. fb N jets = 5 [GeV] data syst. unc. gg X NLO+PS (POWEG+PY8) + X = VBF + V + tt γ γ, s = 8 TeV L dt =. fb m γγ [GeV] 5 Reconstructed N jets * Unfold yields into cross sections using bin-by-bin correction factors * Truth fiducial definition chosen to closely match experimental selection.! Minimizes model dependence. Unfolding Factor.8 Simulation Preliminary N jets Measured 7 variables: iggs p T and rapidity, cos, N jets,leadingjetp T, p +jj, T jj / 8

15 v.b Di erential Cross sections from! iggs p T, helicity angle, and N jets compared with Res, Powheg+Py8, J Minlo+Py8 [fb/gev] T / dp dσ fid Ratio to POWEG Preliminary data gg gg X syst. unc. NLO+PS (POWEG+PY8) + X NNLO+NNLL (RES.) + X = VBF + V + tt γ γ, L s = 8 TeV dt =. fb 8 8 Particle level p [GeV] Tγ γ / d cos(θ*) [fb] dσ fid 8 8 γ γ, L s Preliminary = 8 TeV dt =. fb Compatibility with SM predictions: P-value based on Ratio to POWEG data gg syst. unc. NLO+PS (POWEG+PY8) + X gg +j NLO+PS (MINLO J+PY8) + X X = VBF + V + tt using full experimental + theory covariance Njets p T y cos p j T p jj jj T POWEG MINLO Res..9. Particle level cos(θ*) [fb] σ fid Ratio to POWEG Preliminary Uncertainties from MCFM data gg syst. unc. NLO+PS (POWEG+PY8) + X gg +j NLO+PS (MINLO J+PY8) + X X = VBF + V + tt γ γ, L s = 8 TeV dt =. fb Particle level N jets Statistical limited at this point! Good agreement with SM predictions. le : Displayed are the probabilities from tests for the agreement between the unfolded observaand the theoretical predictions, calculated with the full covariance between bins of the observables. Particle level cos(θ*) Particle level N jets 5 / 8

16 vi.a Summary & Conclusion * Combination of precision mass measurement from! &! ZZ : m =5.5 ± GeV Seems to disfavor single iggs-like boson; compatibility with a single resonance is.5% or a tension of. between both masses is observed, maybe due to strong non-gaussian behavior of systematic uncertainties. * Overall signal production strength combining!,! ZZ,! WW : = Observed coupling compatible with SM iggs * VBF coupling strength from combination: VBF / ggf+tt = ! Evidence of. for VBF production of iggs / 8

17 Assumptions * Results with leading order tree-level motivated framework: Single resonance, +,narrowwidthapprox. * 5modelswith focus on di erent observables: / Couplings to Fermions & Bosons / Custodial Symmetry 5 Vertex loops! All determined couplings compatible with the SM (p-values ranging from -%) * Di erential cross section measurements from! * 7observablesstudied,e.g.iggs p T and helicity angle! All measured distributions compatible with the SM. vi.b Summary & Conclusion m = 5.5 GeV Model: κ V, κ F Model: λ FV, κ VV Model: λ WZ, λ γz, λ FZ, κ ZZ Model: κ g, κ γ κ V κ F λ FV λ WZ κ g κ γ Total uncertainty ± σ ± σ s = 7 TeV Ldt =.-.8 fb Parameter value s = 8 TeV Ldt =.7 fb Combined γ γ, ZZ*, WW* σ σ σ σ σ σ σ σ σ σ σ σ 7 / 8

18 Backup 8 / 8