Higgs boson spin/CP at LHC N. Godinovic (FESB-Split) on behalf of CMS collaboration Outline:...

Higgs boson spin/CPHiggs boson spin/CP at LHC 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

N. Godinovic Four Seas Conference, 29.05-03.06. 2007, Iasi, Romania2

MotivationsMotivations

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 !


SM Higgs mass constraints from the data and theorySM Higgs mass constraints from the data and 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)

ExperimentExperiment SM theorySM theory

The triviality (upper) bound andvacuum stability (lower) bound asfunction of the cut-off scale “triviality” : Higgs self-coupling remains finite

2007: M2007: MHH<153<153 GeV GeV, preliminary, preliminary

Direct limit from LEP: MH > 114.4 GeV


SM Higgs: Productions and decaysSM Higgs: Productions and decays


Resonance in H -> ZZ->4lResonance 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


Higgs boson propertiesHiggs 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)?

222 VFVVH MGg

fFfVf mGg 2

However this properties have to be experimentallyHowever this properties have to be experimentally verifiedverified..


SCP Observables

in H->ZZ->4l


Scalar type HZZ couplingsScalar 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,C0), late on will consider (A,C 0)

001111 001111 TTTZZ

2122121221 pp

M

Cpp

M

BAg

ZZ

001111*

2*

22

ZZ

ZZH

MM

MMM 00 1111


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 SCP cases asymmetry parameter (R) is

defined:

SSCPCP observable observabless in H in HZZZZ44ll

Plane angle distribution:

4321

4321 )()(cos

pppp

pppp

TL

TLR

2coscos1)( F

)2(12

)2(12

)2(1 sin)cos1()( LTG

is measured between two planes defined by lepton decays of two Z bosons in the Higgs rest frame

Polar angle distribution:


Theory: PlaneTheory: Plane a anngglele distributions distributions

2coscos1)( FParameter

-0,03

-0,02

-0,01

0

0,01

0,02

0,03

180 280 380 480

mH(GeV)

Spin 0, CP

Spin 1, CP +

Spin 1, CP

Spin 0, CP +

There are unique theoretical

values of , for different SCP values.

Parameter Parameter


Theory: PolarTheory: Polar a anngglesles distributions distributions::

1

1200

200

T

TR

2200

2 sin3

4)cos1(

3

4

cosT

d

d H SCP 0++

Parameter R

2

22

00 2

22

Z

ZHZH M

MMTMM


Theory Theory && real life real life

0,6

0,7

0,8

0,9

1

1,1

1,2

1,3

0 0,5 1 1,5 2 2,5 3

(rad)

F(

)

SM Higgs (200 GeV) SM Higgs (300 GeV) Pseudoscalar

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.


ATLAS Study

SCP in H->ZZ->4l


Polar and Polar and planeplane angle distribution for angle distribution for SM SM mmHH=200 GeV=200 GeV

Polar angle distribution Decay plane angle distribution

Signal SignalBackground Background

no cuts and detector response only detector acceptance all cuts and smearing

ATLAS hep-ph/0212396

H->ZZ->4l


Expected values and errors for: R, 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

100 fb-1

100 fb-1

Parameter and for mH=200 Gev


Significance for exclusion non SM SSignificance for exclusion non SM SCPCP

SM

NSMSM

error

meanmeanS

22 SSS plane

222¸ Rcom SSSS


ATLAS Study

SCP in WBF & H->WW->2l2


SSCPCP in H->qqWW->qq2l2 in H->qqWW->qq2l2 (WBF) (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, cosll, 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 (?)

Eur.Phys.J.C32S2:19-54,2004

Higgs mH=160 GeV

background

tt+Wt bacground

W W background

MT(GeV)/c2ATLAS-hep-ph/0603209

jj


SSCPCP in VBF & H->2l2 in VBF & H->2l2

Distribution of the tag jets angle for the SM and non SM coupling. jj – angle between jets in transverse plane.

mH=150 GeVL= 30 fb-1


jjjj : : Significance to exclude non SM SSignificance to exclude non SM SCPCP

Mean log likelihood ratio 2ln(LSM/LNSM) obtained from a large number of MC experiments and RMS of the distribution of the likelihood ratio.

0-

NSM 0+

1- 1+

L=30 fbL=30 fb-1-1 VBF &H->2l2VBF &H->2l2


MMllll: : Significance to exclude non SM Significance to exclude non SM

SSCPCP

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

1+

0+

0-

1-

30 fb-1

VBF &H->2l2VBF &H->2l2


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


CP violation in Higgs sectorCP violation in Higgs sector (1) (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)

AIHd 2tantan~)(

212tan

1~ kk

mgC

ZZZ

Acta.P

hys. Polon. V

ol. 38., 738


CP violation in Higgs sectorCP violation in Higgs sector (2) (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.

datax

iBisi

xPDFRxPDFRRL )()1();(log2),(

sample MCin events signal offraction

)()(

21

21

coscos

coscos

R

PPPPPDF

PPPPPDF

BBBM

BB

sSSM

SS

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-


Exclusion significanceExclusion significance

Enhancement (suppression) factor of the signal rate compared to the SM expectation: C2 = BR/SMBRSM

Precison of measurents ~ 1/C

Minimal CMinimal C22 needed to exclude SM Higgs at N needed to exclude SM Higgs at N level level (N=(N=//)) for 60 fb for 60 fb-1-1


SummarySummary 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 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<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

Backup slides


Mean value of ZMean value of Z**- mass distribution for - mass distribution for MMH(A)H(A)<2M<2MZZ

scalar

pseudoscalar

*ZM

d

/d

MZ

*M

Z

*

< MZ* > =39.87 GeV

< MZ* >=39.991 GeV

ZZZZZ

HZZ

H

ZFZ

Z

H

MMM

MMM

M

MGM

dM

d 22222

*

2222*

3

42

* )(

12

16

32

27

sin40

9

sin10

12

7 42WW

Z

ZZZZZ

Z

A

ZFZ

Z

A

MMM

M

M

MGM

dM

d 22222

*

32*

3

62

* )(8

32

Barger et. al., Phys Rev. D49,(1994), 79

Only shape can be used to make distinction between scalar and pseudoscalar

Mean of MZ* mass in H->ZZ->4l

2030

405060

7080

90100

100 200 300 400 500

M_H(GeV)

<MZ

*(G

eV)>

*

2*

22

00 2 ZZ

ZZH

MM

MMMT

ddsdsdsd

dM

dM

d m

o

ZZ

121

3

**

2

2


, , and R bellow m and R bellow mHH<2m<2mZZ

This is valid only above ZZ threshold since the narrow width approximation (NWA) is used for the Z boson propagator

2

22

00 2

22

Z

ZHZH M

MMTMM


To get , and R below ZZ threshold one has to use Finite width approximation (FWA)

)(1 2

2 ZZ

Ms

222 )(

1

ZZZ MMs

Finite width approximation (FWA) valid also for MH<2MZ

(i.e. when one Z is off-shell)

Narrow width approximation (NWA) valid only for MH>2MZ

Angular distribution below ZZ threshold (MAngular distribution below ZZ threshold (MHH<2M<2MZZ))


Calculating Calculating and and below ZZ threshold below ZZ threshold

)(

)(0256,0)(

mF

mAm

)(

)(2)(

mF

mBm

A. Skjold, P. Osland, Phys. Lett. B311(1993)261/265

2cos)(cos)(1 mmd

d

Predictions for (m) and (m) after numerical integration (with Mathematica)

)10221(

48125,51963)

157,8314(

222148125,51963

)157,8314

()( 2121

22

21

42

22

212122

21

1

0

2

1

04

221

1

21

xxxxxx

mmx

xxxxxxdx

mmx

dxmF

x

)1(

48125,51963)

157,8314(

222148125,51963

)157,8314

()( 21

42

22

212122

212

1

0

2

1

04

221

11

21

xx

mmx

xxxxxxxdx

mmx

xdxmA

x

42

22

212122

212

1

0

2

1

04

221

11

48125,51963)

157,8314(

222148125,51963

)157,8314

()(

21

mmx

xxxxxxxdx

mmx

xdxmB

x


Results for Results for and and below threshold below threshold

2coscos1)( F

2*

2

2*

22

00

ZZ

ZZH

MM

MMMT

00

00

22

2

118

3

T

TU

There is unique prediction for and even below ZZ threshold

002

11

1

4

1

T


How to get prediction for R?How to get prediction for R?

1

12

00

200

T

TR we need T00

00

00

22

2

118

3

T

TU

002

11

1

4

1

T

Remainder:

T00

Mean of MZ* mass in H->ZZ->4l

2030

405060

7080

90100

100 200 300 400 500

M_H(GeV)

<MZ

*(G

eV)>

*

2*

22

00 2 ZZ

ZZH

MM

MMMT


mmHH = 150 GeV, = 150 GeV, L = 400 fb-1

R

,, pseudoscalar scalar

Rdata=0,470,09

Rth=0,498

11 single Monte Carlo experiments

cos


ZZ**- mass distribution - mass distribution below thresholdbelow threshold

scalar

pseudoscalar

*ZM

d

/d

MZ

*M

Z

*

ZZZZZ

HZZ

H

ZFZ

Z

H

MMM

MMM

M

MGM

dM

d 22222

*

2222*

3

42

* )(

12

16

32

27

sin40

9

sin10

12

7 42WW

Z

ZZZZZ

Z

A

ZFZ

Z

A

MMM

M

M

MGM

dM

d 22222

*

32*

3

62

* )(8

32

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

Higgs boson spin/CP at LHC N. Godinovic (FESB-Split) on behalf of CMS collaboration Outline:...

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Transcript of Higgs boson spin/CP at LHC N. Godinovic (FESB-Split) on behalf of CMS collaboration Outline:...