1 / 35

SCP Observables and Significance of Non-SM Scalar CP in Higgs Boson Spin at LHC

This study explores the SCP observables and significance of non-SM scalar CP in the spin of the Higgs boson at LHC. Motivations, theoretical models, and experimental constraints are considered, along with the properties of the Higgs boson. The study also investigates SCP observables in H->ZZ->4l and H->WW->2l2v processes. Significance for exclusion of non-SM SCP is analyzed for different scenarios.

fentress
Download Presentation

SCP Observables and Significance of Non-SM Scalar CP in Higgs Boson Spin at LHC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Higgs boson spin/CP at LHC N. Godinovic (FESB-Split) on behalf of CMS collaboration • Outline: • Motivation • SCP observables • Significane for exclusion non SM SCP in H->ZZ->4l • Significance for exclusion non SM SCP in WBF and H->WW->2l2 • Significance for CP violation in H->ZZ->4l

  2. Motivations • Different theoretical models assign different quantum numbers: • SM  1 Higgs boson  scalar, SCP=0++ • MSSM  5 Higgs bosons : • two neutral scalars, SCP=0++ • one neutral pseudoscalar, SCP=0+ • two charged, SCP=0-,0+ • strongly interacting models predicts 1+ 1-, some other model predicts pseudocalar 0-. • CP violation could be present in the Higgs sector !

  3. SM Higgs mass constraints from the data and theory Experiment SM theory Indirect constraints from precision EW data : MH < 260 GeV at 95 %CL (2004) MH < 186 GeV with Run-I/II prelim. (2005) MH < 166 GeV (2006, ICHEP06) The triviality (upper) bound and vacuum stability (lower) bound as function of the cut-off scale L “triviality” : Higgs self-coupling remains finite 2007: MH<153 GeV, preliminary Direct limit from LEP: MH > 114.4 GeV

  4. SM Higgs: Productions and decays

  5. 4 Resonance in H -> ZZ->4l(*) ? • Excess of events is clearly visible in 4l mass spectrum in a mass range expected for the SM Higgs boson, but is it SM Higgs boson ?

  6. Higgs boson properties • SM Higgs is scalar particle 0++ • Once the mass of the SM Higgs boson is known all its properties are known. • coupling strengths to gauge bosons • coupling strengths to fermions • width • Higgs self-couplings • Quantum number spin and CP (SCP)? However this properties have to be experimentally verified.

  7. SCPObservables in H->ZZ->4l

  8.  Scalar type HZZ couplings • Generally Higgs decay H->ZZ produces a system of two Z bosons in the helicity state: • Different couplings give rise to the following characteristic helicity states: • SM Scalar (0++ )(A=1, B=C=0) • Not SM Scalar (0++)”gauge invariant coupling” (B=1, A=C=0) • Not SM Pseudoscalar (0+–) (A=B=0, C=1) • CP violation (A,B,C0), late on will consider (A,C 0)

  9. SCP observables in HZZ4l • Plane angle distribution: •  is measured between two planes defined by lepton decays of two Z bosons in the Higgs rest frame • Polar angle distribution: • 1, 2 are angles between negatively chargedleptons in Z rest frame and direction of motion of corresponding Z in the Higgs rest frame • T – fraction of transversally polarized Z bosons • L – fraction of longitudinally polarized Z bosons • For better differentiation of different SCP cases asymmetry parameter (R) is defined:

  10. Theory: Plane angle distributions There are unique theoretical values of ,  for different SCP values. Parameter  Parameter 

  11. Theory: Polar angles distributions: SCP 0++ Parameter R

  12. Theory & real life Our detectors are very precise but not ideal and we have to understand very detailed how our detector works and how it affects angular distributions and also we have to take in account the background influence in order to find the expected means and errors of the angular parameters in real experiment. Ideal detector large statistics - Real detector

  13. ATLAS Study SCP in H->ZZ->4l

  14. Polar and plane angle distribution for SM mH=200 GeV no cuts and detector response only detector acceptance all cuts and smearing H->ZZ->4l Polar angle distribution Decay plane angle distribution Signal Background Signal Background ATLAS hep-ph/0212396

  15. Expected values and errors for: R, ,  • The error reflects the statistical error form the number of events, the statistical error from the number of background events subtracted and the error made by the estimation of the number of background events. Parameter R as a function of mH Parameter  and  for mH=200 Gev 100 fb-1 100 fb-1

  16. Significance for exclusion non SM SCP

  17. ATLAS Study SCP in WBF & H->WW->2l2

  18. Higgs mH=160 GeV  background tt+Wt bacground W W background SCP in H->qqWW->qq2l2 (WBF) • Higgs signature • Two forward (tag) jets with large  • Two charged leptons in central region with small opening angle ll in transverse plane and high pT • Missing ET • Background suppression • Reject events with jets in central region (between tag jets) • Cuts on PT, Mjj, Mll, ll, cosll, Rll • SCP observables • Distribution of the tag jet angle: jj • Invariant mass of the charged lepton pairs • Distribution of the angle between lepton in transverse plane: ll(?) • jj ATLAS-hep-ph/0603209 MT(GeV)/c2 Eur.Phys.J.C32S2:19-54,2004

  19. SCP in VBF & H->2l2 • Distribution of the tag jets angle for the SM and non SM coupling. jj – angle between jets in transverse plane. L= 30 fb-1 mH=150 GeV

  20. jj: Significance to exclude non SM SCP • Mean log likelihood ratio 2ln(LSM/LNSM) obtained from a large number of MC experiments and RMS of the distribution of the likelihood ratio. L=30 fb-1 VBF &H->2l2 NSM 0+ 0- 1- 1+

  21. 1+ 0+ 0- 1- Mll: Significance to exclude non SM SCP • Feasibility study for exclusion non SM coupling is done by number of MC experiments with expected number of events which give the mean and RMS of the distribution of the mean di-lepton mass. • Exclusion significance=(SM-NSM)/SMRMS VBF &H->2l2 30 fb-1

  22. CP violation H->ZZ->4l CMS feasibility study to measure CP violation H->ZZ->4l p-p at the LHC produce a Higgs boson in mass eigenstate which in CP violation case is not CP eigenstate.

  23. CP violation in Higgs sector (1) • An effective Lagrangian (A. Skojd,P. Osland, Phys.Lett. B329, 305) which has simultaneously scalar and pseudoscalar type coupling between Higgs and vector boson leads to CP violation: • H - scalar (0); I - CP violation term(0< < ±/2) A – pseuodscalar (=±/2) Acta.Phys. Polon. Vol. 38., 738

  24. CP violation in Higgs sector (2) • Parameter  is determined by maximization of the likelihood function L(,R) constructed from the angular distribution and the invariant mass distribution of the four leptons. 200 MC experiments for each value of  and Higgs mass at 60 fb-1 : mean and RMS of  - expected values and uncertainty in real experiment (/2) 0- 0+

  25. Exclusion significance • Enhancement (suppression) factor of the signal rate compared to the SM expectation: C2 = BR/SMBRSM • Precison of  measurents ~ 1/C Minimal C2 needed to exclude SM Higgs at N level (N=/) for 60 fb-1

  26. Summary • H assures spin 0 or 2,1 is excluded (Yang’s Theorem) • Spin 0 should be easily confirmed by an isotropic distribution of two gammas! • VBF and decay H->WW->2l2 have the largest discovery potential for mH<2MZ) and it also provide very promising prospects to confirm the SCP quantum numbers of an SM Higgs with mass between 130 and 180 GeVusing an integrated luminosity of 30 fb-1. • H->ZZ(*)->4l: Discovery is possible with less than 10 fb-1 in a wide range of mass: 130<mH<160 and 2mZ<mH<550 GeV. • Angular correlation in H->ZZ->4l make possible to determine ZZ-coupling and the measurement of CP violation is feasible

  27. Backup slides

  28. < MZ* > =39.87 GeV d/dMZ*MZ* scalar pseudoscalar < MZ* >=39.991 GeV Mean value of Z*- mass distribution for MH(A)<2MZ Barger et. al., Phys Rev. D49,(1994), 79 Only shape can be used to make distinction betweenscalar and pseudoscalar

  29. ,  and R bellow mH<2mZ • This is valid only above ZZ threshold since the narrow width approximation (NWA) is used for the Z boson propagator

  30. Angular distribution below ZZ threshold (MH<2MZ) • To get , and R below ZZ threshold one has to use Finite width approximation (FWA) Narrow width approximation (NWA)valid only for MH>2MZ Finite width approximation (FWA) valid also for MH<2MZ (i.e. when one Z is off-shell)

  31. Calculating  and  below ZZ threshold • A. Skjold, P. Osland, Phys. Lett. B311(1993)261/265 • Predictions for (m) and (m) after numerical integration (with Mathematica)

  32. Results for  and  below threshold There is unique prediction for  and  even below ZZ threshold

  33. How to get prediction for R?  we need T00 • Remainder: T00

  34. pseudoscalar scalar mH = 150 GeV, L = 400 fb-1 • 11 single Monte Carlo experiments Rdata=0,470,09 Rth=0,498 R ,

  35. Z*- mass distribution below threshold • Barger et. al., Phys Rev. D49,(1994), 79 • To distinguish between scalar and pseudoscalar we use shape of distribution • Other possibility: use maximum mH=150 GeV d/dMZ*MZ* scalar pseudoscalar

More Related