- 103 Views
- Uploaded on
- Presentation posted in: General

Searches for Non-Minimal Higgs Bosons

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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Searches for Non-Minimal

Higgs Bosons

Andre S. Turcot

Brookhaven National Laboratory

for the

DØ Experiment at Fermilab

With many thanks to: A. Haas, A. Kharchilava and G. Watts

Outline

- A SUSY Higgs Primer
- Searching for hbb
- Doubling your fun with H++
- h gg : Pushing beyond LEP

A SUSY Higgs Primer

- Addition of a second scalar doublet results in 5 physical higgs bosons

h, H, A, H+, H-

- Standard Model Yukawa couplings modified:
- hbb : sin(b - a) - tanb cos (b – a)
- Hbb:cos(b - a) + tanb sin(b – a)
- Abb: tan b

- Two interesting cases arise for large tan b
- CP Even states can flip-flop playing the role of SM higgs
- M(A) >> M(Z) cos(b - a) << 1
- M(A) ~ M(H), Hbb coupling tan b
- M(A) <~ M(Z) cos(b - a) ~1
- M(A) ~ M(h), hbb coupling tanb

SUSY Higgs Production

- When tan b is large two of the three
- Neutral Higgs bosons will have enhanced bb couplings

CP-odd HiggsProduction

CP-even HiggsProduction

SUSY Higgs: The RunII Angle

- Much theoretical progress since RunII SUSY-Higgs Wkshp
- Recent work indicates that the LO cross-sections are an underestimate by a factor ~3 (e.g. hep-ph/0204093)
- Better understanding of NLO effects, scale dependencies
- Theoretical bias towards expecting large tan
- b-τ Yukawa unification at the GUT scale
→ mt/mb ~ tan ~ 50

- b-τ Yukawa unification at the GUT scale
- Since cross section scales astan2there will be a huge enhancement, O(1000) for motivated values
- Leads to an interesting complementarity with LEP as Tevatron can probe high tan bregion of parameter space where small sin(b - a) and/or kinematics preclude hA, HA, Zh ZH production at LEP

Triggering on bb(h,H,A):

- Multi-Level Trigger:
- Level 1: Require 3 trigger towers of 5 GeV
- Level 2: Require 3 jets of 8 GeV, HT > 50 GeV
- Level 3: 3 Jets 15 GeV, 2 of 25 GeV, primary vtx within SMT
- Rates at L ~ 60E30 are 280/100/6 Hz

Done for all trigger components

- Efficiencies relative to off-line selection are excellent
e.g. for M=120 4 jets of 45, 35, 2x15 GeV (0.5 cone algorithm)

Secondary Vertex Tag

Algorithm

Extra Loose Operating Point

Light j ~ 2%

Many improvements

in the works

Improved Tracking

Improved Alignment

Improved Algorithms

hbb

This represents only the first “sketches” in the art of b-tagging

Quadruple b-tagged event

Search for bb(h,H,A):

Leading Backgrounds:

jjjj with multiple fakes

bb jj with fake (8% ccjj)

Zbb and bbbb are small

Comparison of double b-tagged events with ≥4 jets to Monte Carlo

The ALPGEN Monte Carlo describes the multi-jet heavy-flavor background very well.

We have measured the normalization factor of data / MC :

1.14±0.02(stat.)

≥ 4 jets≥ 2 b-tags

Search for bb(h,H,A):

Comparison of triple b-tagged events to expected background

The background shape was extrapolated from double b-tagged data using a tag-rate-function derived on the full multi-jet data sample.

Limits were set on the signal production, using simulated signal shapes, the normalized background, and the observed data.

Excluded Signal

≥ 3 jets≥ 3 b-tags

Systematic Errors on Acceptance (%)

Dominated by JES: Ongoing efforts to improve

Systematic Errors on Backgrounds…

Both b-id related and statistics

8-11% depending upon the optimized point

Search for bb(h,H,A):

Constraints in the MSSM parameter space

Limits will continue to improve with:

More data

Better b-tagging

Better triggers

Expect new results soon!

131 pb-1 of data

Note Complementarity with LEP

Search for Doubly-Charged Higgs

Many models predict the existence of Higgs bosons with twice the electric charge of other particles:

- Left/Right Symmetric
- Higgs Triplet
- Little Higgs
We search for decays of the doubly-charged Higgs into two like-signed muons.

Assume a 100% branching ratio to muons when setting limits

Coupling depends on L/Rhandedness

Feynman diagram for the production of doubly-charged Higgs

Search for Doubly-Charged Higgs

Comparisons of mass and Δφ distributions of the di-muon data to Monte Carlo

Good agreement before requirment of Like Sign muons

Search for Doubly-Charged Higgs

Comparisons of mass and Δφdistributions of the like-signed and isolated di-muon data to Monte Carlo

No evidence of excess in like-sign isolated muons:

3 candidates vs 1.5 +/- 0.4 expected

Search for Doubly-Charged Higgs

Confidence Limit set as a function of doubly-charged (left-handed) Higgs mass

Set limits on the masses of doubly-charged Higgs bosons:

mHL ++ > 118.4 GeV

mHR ++ > 98.2 GeV

113 pb-1

On going efforts to improve

Double the data set

Include t t, WW channels

Search for Higgs→ γγ

Some models predict an enhanced branching fraction of Higgs bosons to two photons:

- Top-color Higgs
- Fermio-phobic Higgs
“Boso-phillic” at U of C

Total bkgd.

QCD

Other

Error on BG

Reasonable agreement

with expected background

Di-photon Invariant mass

Search for Higgs → γγ

No evidence of excess

Set limits as a function

of branching ratio

assuming model dependent

production cross-section

Can extend LEP Reach

With current data but mass limits will require more data

Future Analyses will benefit from improved g ID

Conclusions

has searched for non-minimal Higgs bosons

- Data sets of 113 to 195 /pb studied
- Results on hbb, H++ and h gg

- Unfortunately with no hint of a signal
- Improvments to all channels in progress Attacking the key issues, b-tagging, JES
- Stay tuned for more exciting results