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Searches for Higgs Bosons Beyond the Standard Model with the CMS - - PowerPoint PPT Presentation

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Searches for Higgs Bosons Beyond the Standard Model with the CMS Experiment at the LHC Roger Wolf 18./19. November 2014 INSTITUTE OF EXPERIMENTAL PARTICLE PHYSICS (IEKP) PHYSICS FACULTY KIT University of the State of Baden-Wuerttemberg

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KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

INSTITUTE OF EXPERIMENTAL PARTICLE PHYSICS (IEKP) – PHYSICS FACULTY

www.kit.edu

Searches for Higgs Bosons Beyond the Standard Model with the CMS Experiment at the LHC

Roger Wolf 18./19. November 2014

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Road map...

  • Short recap:
  • What do we know about the Higgs boson and how much space is still left for new physics in

the Higgs sector?

  • Higgs bosons – what it is about?
  • Higgs decays to invisible ( ) and related statement on DM interactions.
  • Search for additional supersymmetric Higgs bosons:
  • In the MSSM there are five Higgs bosons and we make strong statements on all of them!
  • There is one detour in this, on an analysis of LFV in the Higgs

sector.

Disclaimer:

This is a personal choice and by no means complete.

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About Higgs: a short recap...

  • Need Higgs mechanism to explain how particles can have mass and at the

same time symmetry can be source of electroweak interactions.

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About Higgs: a short recap...

  • Need Higgs mechanism to explain how particles can have mass and at the

same time symmetry can be source of electroweak interactions.

  • Symmetry inherent to a system but not to its

energy ground state (→ quantum vacuum).

  • In a quantum field theory (QFT) this can create

new physical particles (→ Higgs boson(s)).

Non-zero vacuum expectation value

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About Higgs: a short recap...

  • Need Higgs mechanism to explain how particles can have mass and at the

same time symmetry can be source of electroweak interactions.

  • Symmetry inherent to a system but not to its

energy ground state (→ quantum vacuum).

  • A Higgs boson has very a peculiar coupling structure, needed to fulfill the

symmetry of the system (example for fermions):

  • In a quantum field theory (QFT) this can create

new physical particles (→ Higgs boson(s)).

Non-zero vacuum expectation value

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Higgs: a known suspect

4th of July 2012

  • We know it exists ( )!

arXiv:1207.7235

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Higgs: a known suspect

4th of July 2012

  • We know its a boson.
  • We know it exists ( )!

arXiv:1207.7235 arXiv:1407.0558 arXiv:1312.5353

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Higgs: a known suspect

  • We know its mass ( ):

4th of July 2012

CMS-PAS-HIG-14-009

  • We know its a boson.
  • We know it exists ( )!

arXiv:1207.7235 arXiv:1407.3792 Overall fit of electroweak precision

  • bservables

arXiv:1407.0558 arXiv:1312.5353

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Higgs: a known suspect

  • We have strong evidence that it couples to

fermions ( ).

  • We know its mass ( ):

4th of July 2012

CMS-PAS-HIG-14-009

  • We know its a boson.
  • We know it exists ( )!

arXiv:1207.7235 arXiv:1401.6527 arXiv:1401.5041 arXiv:1401.6527

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Higgs: a known suspect

  • We have strong evidence that it couples to

fermions ( ).

  • We know its mass ( ):

4th of July 2012

CMS-PAS-HIG-14-009

  • We know its a boson.
  • We know it exists ( )!

arXiv:1207.7235 arXiv:1401.6527

  • We have reasons to believe that it is a

spin 0 even object ( ).

arXiv:1312.5353 arXiv:1312.5353

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Higgs: a known suspect

  • We have strong evidence that it couples to

fermions ( ).

  • We know its mass ( ):

4th of July 2012

CMS-PAS-HIG-14-009

  • We know its a boson.
  • We know it exists ( )!

arXiv:1207.7235 arXiv:1401.6527

  • We have reasons to believe that it is a

spin 0 even object ( ).

arXiv:1312.5353

for fermions for vector bosons

  • We know it's a Higgs boson!
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Higgs: a known suspect

  • We have strong evidence that it couples to

fermions ( ).

  • We know its mass ( ):

4th of July 2012

CMS-PAS-HIG-14-009

  • We know its a boson.
  • We know it exists ( )!

arXiv:1207.7235 arXiv:1401.6527

  • We have reasons to believe that it is a

spin 0 even object ( ).

arXiv:1312.5353

for fermions for vector bosons

  • We know it's a Higgs boson!

I s t h i s T H E H i g g s b

  • s
  • n

(of the

SM) or is it just A Higgs boson?

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Why it is not THE Higgs boson (of the SM) (1)

  • Gravity is not included in the SM.
  • Dark matter is not included in the SM.
  • The SM suffers from the hierarchy problem.
  • Neutrino masses are not included in the SM.
  • There are known deviations in

from the SM expectation ( unresolved).

(1) Arguments stolen from S. Heinemeyer (HH Higgs workshop 2014)

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Why it is not THE Higgs boson (of the SM) (1)

  • Gravity is not included in the SM.
  • Dark matter is not included in the SM.
  • The SM suffers from the hierarchy problem.
  • Neutrino masses are not included in the SM.
  • There are known deviations in

from the SM expectation ( unresolved).

  • There must be physics beyond

the SM!

  • At what scale does it set in?
  • (How) Does it influence the

Higgs sector?

arXiv:hep-ph/0003170

(1) Arguments stolen from S. Heinemeyer (HH Higgs workshop 2014)

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Space left for new physics in the Higgs sector

  • Couplings are determined within to accuracy.

CMS-PAS-HIG-14-009

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Space left for new physics in the Higgs sector

  • Couplings are determined within to accuracy.
  • Fixing all tree-level couplings to the SM ( ) & introducing effective

couplings for loop induced processes ( ) leaves room for @ 95% CL.

CMS-PAS-HIG-14-009

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Space left for new physics in the Higgs sector

  • Couplings are determined within to accuracy.
  • Fixing all tree-level couplings to the SM ( ) & introducing effective

couplings for loop induced processes ( ) leaves room for @ 95% CL.

  • Adding maximal freedom to the fit leaves room for @ 95% CL.

CMS-PAS-HIG-14-009

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arXiv:1404.1344

Direct searches for ( )

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arXiv:1404.1344

Direct searches for ( )

s-channel

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q q

58% (obs) 44% (exp)

arXiv:1404.1344

Direct searches for ( )

s-channel t-channel

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arXiv:1404.1344

Direct searches for ( )

q q

s-channel t-channel

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SUSY particles as DM candidates

  • Extension of SM by a last remaining, non-trivial, symmetry operation (boson ↔

fermion), SUSY, can cure many shortcomings of SM:

  • E.g. lightest SUSY particle (LSP) perfect candidate for .
  • Problem: SUSY itself is broken!
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Higgs sector in the MSSM

  • Five neutral Higgs bosons predicted:
  • MSSM mass requirements at tree level:

arXiv:hep-ph/0503173

two free parameters: ,

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( )

Enhancement of down-type couplings

  • In MSSM coupling to down-type fermions enhanced for .
  • Interesting decay channels:

expect MSSM here!

  • Interesting production modes:

(“ ”) ( ) (“ ”)

CMS-PAS-HIG-14-009

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Search for ( )

Six decay modes:

  • Search for 2 isolated high leptons

( , , ).

  • Reduce obvious backgrounds (use on

) & reconstruct .

  • Exploit characteristics of production

mode to increase sensitivity.

arXiv:1408.3316

  • f all

decay modes.

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Reconstruction of hadronic

Compatible w/ mass requirements

  • Isolation (based on energy deposits in

vicinity of reconstructed candidate).

  • Discrimination against electrons (based
  • n shower shape & ).
  • Discrimination against muons.
  • Exploit particle flow algorithm: distinguish

between , and .

  • Allows for independent cross check of

energy calibration (use 3% uncert.).

  • Efficiency ( fakerate), flat

as function of and .

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Reconstruction of

  • Likelihood approach:
  • Inputs: visible decay products, x-, y-

component of .

  • Free parameters: , , ( ) per .

Resolution:

  • ME for leptonic decay or phase space

kinematics of 2-body decay of .

  • Find minimum of for given and

scan over all possible values of to find global minimum.

  • Estimate of expected resolution on

event by event basis.

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Control of backgrounds

  • From simulation.
  • Normalization from

sideband.

  • Normalization &

shape taken from LS/OS or fakerate.

  • From simulation
  • Corrected for
  • r fakerate.
  • From simulation
  • Normalization from

sidebands.

Taken from arXiv:1401.5041

  • Apply semi-analytic fits in

tails.

  • Embedding (in

replace by sim ).

  • Norm from .
  • Full consideration of uncert.

due to limited statistics in control or MC samples in bulk

  • f distributions.
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Event categorization

  • Exploit enhancement of coupling to down-type fermions for initial state (→ b-quarks).

b-tag category: No b-tag category:

  • Sensitive to both production modes!
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Model independent limits (2D)

  • Single narrow resonance search in & production mode:
  • Most probable value and 2D limit

contour from scan of likelihood function ( NLL points).

  • Find DB of full likelihood scan in 3D ( ,

, ) on supporting TWiki for .

arXiv:1408.3316

… (for 31 mass points btw. 90 and 1000 GeV,

→ scan points).

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Model independent limits (1D)

  • 1D limit contours obtained from 2D by profiling non-observed component:

has been profiled has been profiled

Sensitivity to h(125) of ~2.5 σSM.

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Limits in full MSSM benchmark scenarios

  • Explicit prediction for three neutral Higgs bosons:
  • Note: h(125) has been observed!
  • With increasing sensitivity new

statistical interpretation is needed: “1 Higgs vs 3 Higgses”.

  • Old method: h(125) ignored in

statistical inference:

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Limits in full MSSM benchmark scenarios

  • Explicit prediction for three neutral Higgs bosons:
  • Note: h(125) has been observed!
  • With increasing sensitivity new

statistical interpretation is needed: “1 Higgs vs 3 Higgses”.

  • New method: h(125) taken into account

in test statistic:

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More benchmark scenarios...

enhanced reduced reduced (arXiv:1302.7033)

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LFV Higgs couplings ( )

  • SM forbids LFV couplings at tree level.
  • analysis w/ two specialties:
  • Three couplings are possible: ,

, .

  • LVF could take place in Higgs sector.

Limits in literature:

  • is harder (→ less in the decay).
  • are more collinear. Use of collinear

approximation for .

CMS-PAS-HIG-14-005

  • .
  • .
  • .
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LFV Higgs search results

excess

1.57% @ 95% CL Distribution shown in previous slide.

Strongest limits on the market!

Distribution in backup.

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Charged Higgs in the MSSM

  • Expect signal in top sector:

arXiv:hep-ph/0503173

  • In the decay ( ):
  • In the decay ( ):

heavy flavors preferred flavor democratic additional b jets

CMS-PAS-HIG-14-020 CMS-PAS-HIG-13-026 CMS-PAS-HIG-13-035 details in backup

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Charged Higgs boson search ( )

  • Most sensitive decay channel (cf neutral Higgs searches).
  • Concentrate on hadronic decay of W →

well defined use of for sig extraction.

  • Extending mass range of search by

.

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  • Translated into plane.

Charged Higgs boson search ( )

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  • Translated into plane.
  • Combining both measurement will close the plane in the

range .

Charged Higgs boson search ( )

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Conclusions

  • CMS consolidating BSM Higgs searches on LHC-

1 dataset by end of this year.

  • searches (in and final states).
  • LHC had an extremely successful run-1 data taking period.
  • Greatest prey was the Higgs boson!
  • Unfortunately no further new physics discovered,
  • yet. Good hunting grounds are the top and the

Higgs sector, apart from conventional SUSY harvesting.

  • Shown here only a very small and personal excerpt of most important results (others

will be come more interesting from 2015 on):

CMS-PAS-HIG-14-013 CMS-PAS-HIG-13-032

  • searches ( ), w/ first interpretations in general 2HDMs.

CMS-PAS-HIG-14-011

  • … .

das Higgs

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das Higgs

Conclusions

  • CMS consolidating BSM Higgs searches on LHC-

1 dataset by end of this year.

  • searches (in and final states).
  • LHC had an extremely successful run-1 data taking period.
  • Greatest prey was the Higgs boson!
  • Unfortunately no further new physics discovered,
  • yet. Good hunting grounds are the top and the

Higgs sector, apart from conventional SUSY harvesting.

  • Shown here only a very small and personal excerpt of most important results (others

will be come more interesting from 2015 on):

CMS-PAS-HIG-14-013 CMS-PAS-HIG-13-032

  • searches ( ), w/ first interpretations in general 2HDMs.

CMS-PAS-HIG-14-011

  • … .

L

  • k

i n g f

  • r

w a r d t

  • L

H C r u n

  • 2

!

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Backup

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  • Start off from regular analysis in the and the channel ( ):

Charged Higgs boson search ( )

  • Discriminate signal from

background via .

  • Take into account signal in

& in .

still a factor ~5 from being discriminative within this benchmark model

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Charged Higgs boson search ( )

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Charged Higgs boson search ( )

i.e. ignoring i.e. ignoring

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  • Start off from regular analysis in channel (based on 20fb-1 on 8 TeV).

Charged Higgs boson search ( )

  • Reconstruct from kinematic fit (using ).

Limit on :

CMS-PAS-HIG-13-035

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Charged Higgs boson search ( )

arXiv:1407.6643

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Performance of hadronic reconstruction

  • Control energy scale within from fits to

:

  • Control efficiency within

using tag & probe methods:

  • Uncertainties further constrained by maximum

likelihood fit in the statistical inference for signal extraction.

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Performance of hadronic reconstruction

  • Efficiency ( fake rate), flat for & independent from PU.
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MSSM model dependency

  • In the SM analysis we chose nearly 100 different event categories. Why not choose

more categories in MSSM analysis?

  • In spectra of Higgs bosons

change with other particles in loop:

  • Checked with pure b and pure t in

loop from pythia that current categorization is not sensitive.

  • Refrained from categorization that

depends on Higgs .

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Model independent limits (2D)

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Model independent limits (2D)

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More benchmark scenarios... (new method)

enhanced reduced reduced

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More benchmark scenarios... (old method)

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Input distributions

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  • Within the SM is out of reach for current analyses.
  • But in BSM models like Warped Extra Dimensions (WED) can be

enhanced by several orders of magnitude.

  • This motivates searches for resonant decay into (“SM”) Higgs bosons:

CMS-PAS-HIG-13-032

  • High resolution of .
  • High BR of .

CMS-PAS-HIG-14-013

  • High BR of .

strong mass constraint narrow resonance (→ 1 GeV)

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  • Same reconstruction as for cut based SM cross check analysis.
  • Two event categories: medium(high) purity → 1(2) b-tagged jets.
  • Improved (b-)jet energy resolution by kinematic fit (cf. 4b analysis).
  • Window on

& .

  • Extract signal

from .

  • Window on

& .

  • Extract signal

from . Signal extracted from parametric signal & background model.

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  • Select 4 b-jets w/ highly efficient b-tagging algorithm (CVMVA , ).
  • Improved (b-)jet energy resolution by kinematic fit (20-40%).
  • Distinguish high(low) mass region for association of b-jets to h(125) candidate.
  • Extract signal from parametric signal and BG model (→BG: 20% , 80% QCD).
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: Template validation

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: Spin-0 result

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: Spin-2 result