Higgs Measurements at a Muon Collider Higgs Factory [Preliminary] - PowerPoint PPT Presentation

Higgs Measurements at a Muon Collider Higgs Factory [Preliminary] Alexander Conway, UChicago Muon Collider Detector Research and Design Group aconway@fnal.gov 1 Muon Collider Detector Research and Desi gn

Machine Parameters ● Average luminosity: ● Integrated luminosity: (4.2 fb^-1) ● Number of Higgs: 71264 ● Beam spread: (0.004%) ● aconway@fnal.gov, Muon Collider Detector 2 Research and Design

Higgs Parameters ● M_h = 125GeV ● Gamma_h = 4.07GeV – Br(h->bb) = 0.577 – Br(h->WW*) = 0.215 – Br(h->ta+ta-) = 0.063 ● (from LHC Higgs Cross Section Working Group - arXiv:1201.3084v1) ● Initial state radiation reduces Higgs effective cross section to 53% – Cite Estia? aconway@fnal.gov, Muon Collider Detector 3 Research and Design

Channels ● Bb – ~80% efficiency (compare to ILC Z->bb tagging) – Background from gamma*/Z (do energy cuts? -do both) ● ● WW* – H → WW* → l + nu + (l + nu or jj) (~ 54%) – No background ● Tau+tau- – 100% efficiency? – Background from gamma*/Z (do cuts? - do both) aconway@fnal.gov, Muon Collider Detector 4 Research and Design

Channels b-bbar ● Signal: – Raw: 18.2pb – 53% ISR * 80% b-tag: ● 7.7pb (assume purity=1) – 52% (Energy/event shape cuts) ● 4.0pb ● Background: – Raw: 57.2pb – 80% b-tag ● 42.2pb – 15% (Energy/event shape cuts) ● 6.3pb aconway@fnal.gov, Muon Collider Detector 5 Research and Design

Channels WW* tau+ tau- ● Require lepton and neutrino with ● Perfect tagging? – Two jets or ● h->tau+ tau- is – Lepton + neutrino – Raw: 2.0pb ● 54% of WW* events – 53% (ISR): ● h->WW* is ● 1.1pb – Raw: 6.8pb – 80% (Energy/event shape cuts): – 53% (ISR) * 54% (Br) ● 0.8pb ● Background is ● 1.9pb ● Background is – Raw: 12.8pb – Nothing (0.001pb because my – 40% (Energy/event shape cuts): program requires non-zero ● 5.1pb background) aconway@fnal.gov, Muon Collider Detector 6 Research and Design

Cross Sections Channel Signal x-sect Background x- S/B S/sqrt(B) @ (pb) sect (pb) 4fb^-1 Bb – no cuts* 7.7 42.2 0.18 75 Bb - cuts** 4.0 6.3 0.63 101 WW* 1.9 0.001 --- --- ta+ta- - no cuts 2.0 12.8 0.16 35.4 ta+ta- - cuts** 0.8 5.1 0.16 22.4 *ISR correction and b-tagging applied **Energy and event shape cuts from report ● ISR reduces tau+tau- enough that no cuts is better. aconway@fnal.gov, Muon Collider Detector 7 Research and Design

Data Simulation and Fitting ● Poisson statistics – Generate random values from Poisson distribution with expected value of (L/step)*(s+b). – Error = sqrt(N) ● Data points separated by beam spread ● How many points to take? – Try different numbers and use however many optimize fit? – How to quote #Higgs/yr if we are taking most data off-peak? aconway@fnal.gov, Muon Collider Detector 8 Research and Design

Data Simulation and Fitting ● Fit function: – Breit-Wigner convoluted with Gaussian beam spread, multiplied by ISR correction and branching fraction, plus background cross section, times integrated luminosity per point. ● Fitting algorithm: – Residual: [(fit – data)/(data error)]^2 ● Minimize residual (Pearson's cumulative chi-square test statistic) with MIGRAD – Find errors in MIGRAD fit with MINOS ● Full non-parabolic error calculation ● Free Parameters: – Higgs mass, Higgs width, branching fraction ● Given Parameters: – Integrated luminosity, background cross section, signal efficiency, beam spread, initial state radiation correction aconway@fnal.gov, Muon Collider Detector 9 Research and Design

Data Simulation and Fitting Quality of Fit ● Simulate new data and aconway@fnal.gov, Muon Collider Detector 10 Research and Design

B-bbar with cuts aconway@fnal.gov, Muon Collider Detector 11 Research and Design

aconway@fnal.gov, Muon Collider Detector 12 Research and Design

Data Simulation and Fitting Channel Signal x- Background Fitted Mass Fitted Width Fitted sect (pb) x-sect (pb) (MeV) (MeV) Branching Fraction Bb – no cuts* 7.7 42.2 0.06+-0.3 3.9+-0.5 0.58+-0.01 Bb - cuts** 4.0 6.3 0.10+-0`.14 4.14+-0.3 0.583+-0.005 WW* 1.9 0.001 0.27+-0.02 ta+ta- - no cuts 2.0 12.8 ta+ta- - cuts** 0.8 5.1 *ISR correction and b-tagging applied **Energy and event shape cuts from report ● ISR reduces tau+tau- enough that no cuts is better. aconway@fnal.gov, Muon Collider Detector 13 Research and Design