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

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

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

N. Godinovic Four Seas Conference, , Iasi, Romania 4 SM Higgs: Productions and decays

N. Godinovic Four Seas Conference, , Iasi, Romania 5 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 ? 44

N. Godinovic Four Seas Conference, , Iasi, Romania 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 (S CP )? However this properties have to be experimentally verified. verified.

N. Godinovic Four Seas Conference, , Iasi, Romania 7 S CP Observables in H->ZZ->4l

N. Godinovic Four Seas Conference, , Iasi, Romania 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)  

N. Godinovic Four Seas Conference, , Iasi, Romania 9   1,  2 are angles between negatively charged leptons 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 S CP cases asymmetry parameter (R) is defined: S CP observables in H  ZZ  4 l  Plane angle distribution:   is measured between two planes defined by lepton decays of two Z bosons in the Higgs rest frame  Polar angle distribution:

N. Godinovic Four Seas Conference, , Iasi, Romania 10 Theory: Plane angle distributions There are unique theoretical values of ,  for different S CP values. Parameter  Parameter 

N. Godinovic Four Seas Conference, , Iasi, Romania 11 Theory: Polar angles distributions: S CP  0 ++ Parameter R

N. Godinovic Four Seas Conference, , Iasi, Romania 12 Theory & real life Ideal detector large statistics - Real detector 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.

N. Godinovic Four Seas Conference, , Iasi, Romania 13 ATLAS Study S CP in H->ZZ->4l

N. Godinovic Four Seas Conference, , Iasi, Romania 14 Polar and plane angle distribution for SM m H =200 GeV Polar and plane angle distribution for SM m H =200 GeV Polar angle distribution Decay plane angle distribution Signal Background no cuts and detector response only detector acceptance all cuts and smearing ATLAS hep-ph/ H->ZZ->4l

N. Godinovic Four Seas Conference, , Iasi, Romania 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 m H 100 fb -1 Parameter  and  for m H =200 Gev

N. Godinovic Four Seas Conference, , Iasi, Romania 16 Significance for exclusion non SM S CP

N. Godinovic Four Seas Conference, , Iasi, Romania 17 ATLAS Study S CP in WBF & H->WW->2l2

N. Godinovic Four Seas Conference, , Iasi, Romania 18 S CP 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 p T  Missing E T  Background suppression  Reject events with jets in central region (between tag jets)  Cuts on P T, M jj, M ll,  ll, cos  ll,  R ll  S CP 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 (?) Eur.Phys.J.C32S2:19-54,2004 Higgs m H =160 GeV  background tt+Wt bacground W W background M T (GeV)/c 2 ATLAS-hep-ph/  jj

N. Godinovic Four Seas Conference, , Iasi, Romania 19 S CP in VBF & H->2l2 S CP in VBF & H->2l2  Distribution of the tag jets angle for the SM and non SM coupling.  jj – angle between jets in transverse plane. m H =150 GeVL= 30 fb-1

N. Godinovic Four Seas Conference, , Iasi, Romania 20  jj : Significance to exclude non SM S CP  Mean log likelihood ratio 2ln(L SM /L NSM ) obtained from a large number of MC experiments and RMS of the distribution of the likelihood ratio NSM L=30 fb -1 VBF &H->2l2 VBF &H->2l2

N. Godinovic Four Seas Conference, , Iasi, Romania 21 M ll : Significance to exclude non SM S CP  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)/SM RMS fb -1 VBF &H->2l2 VBF &H->2l2

N. Godinovic Four Seas Conference, , Iasi, Romania 22 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. CP violation H->ZZ->4l

N. Godinovic Four Seas Conference, , Iasi, Romania 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

N. Godinovic Four Seas Conference, , Iasi, Romania 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 0+ (  /2) 0 -

N. Godinovic Four Seas Conference, , Iasi, Romania 25 Exclusion significance  Enhancement (suppression) factor of the signal rate compared to the SM expectation: C 2 =  BR/  SM BR SM   Precison of  measurents  ~ 1/C Minimal C 2 needed to exclude SM Higgs at N  level (N=  /   ) for 60 fb -1

N. Godinovic Four Seas Conference, , Iasi, Romania 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 m H <2M Z ) and it also provide very promising prospects to confirm the S CP quantum numbers of an SM Higgs with mass between 130 and 180 GeV using 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<m H <160 and 2m Z <m H <550 GeV.  Angular correlation in H->ZZ->4l make possible to determine  ZZ-coupling and the measurement of CP violation is feasible

Backup slides

N. Godinovic Four Seas Conference, , Iasi, Romania 28 Mean value of Z * - mass distribution for M H(A) <2M Z scalar pseudoscalar d  /dM Z*  M Z* =39.87 GeV = GeV Barger et. al., Phys Rev. D49,(1994), 79 Only shape can be used to make distinction between scalar and pseudoscalar

N. Godinovic Four Seas Conference, , Iasi, Romania 29 ,  and R bellow m H <2m Z ,  and R bellow m H <2m Z  This is valid only above ZZ threshold since the narrow width approximation (NWA) is used for the Z boson propagator

N. Godinovic Four Seas Conference, , Iasi, Romania 30  To get ,  and R below ZZ threshold one has to use Finite width approximation (FWA) Finite width approximation (FWA) valid also for M H <2M Z (i.e. when one Z is off-shell) Narrow width approximation (NWA) valid only for M H >2M Z Angular distribution below ZZ threshold (M H <2M Z )

N. Godinovic Four Seas Conference, , Iasi, Romania 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)

N. Godinovic Four Seas Conference, , Iasi, Romania 32 Results for  and  below threshold There is unique prediction for  and  even below ZZ threshold

N. Godinovic Four Seas Conference, , Iasi, Romania 33 How to get prediction for R?  we need T 00  Remainder: T 00

N. Godinovic Four Seas Conference, , Iasi, Romania 34 m H = 150 GeV, m H = 150 GeV, L = 400 fb -1 R , , , ,  pseudoscalarscalar R data =0,47  0,09 R th =0,498  11 single Monte Carlo experiments

N. Godinovic Four Seas Conference, , Iasi, Romania 35 Z * - mass distribution below threshold scalar pseudoscalar d  /dM Z*  M Z*  Barger et. al., Phys Rev. D49,(1994), 79  To distinguish between scalar and pseudoscalar we use shape of distribution  Other possibility: use maximum m H =150 GeV