Charged Higgs Results from Tevatron Sudeshna Banerjee ta Institute of Fundamental Research Mumbai, India For CDF and DØ Collaborations Fermilab, Chicago Beijing ICHEP04 Beijing, China Aug 16, 2004 What are Doubly Charged Higgs How do we look for them at the Tevatron Did we find them What can we say about their properties from experimental data ?
Sudeshna Banerjee. Beijing. Fermilab, Chicago. Tata Institute of Fundamental Research. Mumbai, India. For CDF and D Ø Collaborations. ?. What are Doubly Charged Higgs How do we look for them at the Tevatron Did we find them What can we say about their properties from experimental data. - PowerPoint PPT Presentation
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Charged Higgs Results from Tevatron
Sudeshna Banerjee
Tata Institute of Fundamental Research
Mumbai, India
For CDF and DØ Collaborations
Fermila
b, Chicago
Beijing
ICHEP04 Beijing, ChinaAug 16, 2004
What are Doubly Charged Higgs How do we look for them at the Tevatron Did we find them What can we say about their properties from
experimental data
What are Doubly Charged Higgs How do we look for them at the Tevatron Did we find them What can we say about their properties from
experimental data??
ICHEP04, Beijing, August 16, 20042Sudeshna Banerjee
ICHEP04, Beijing, August 16, 20043Sudeshna Banerjee
Doubly Charged Higgs Bosons appear in several models L-R Symmetric models, Little Higgs model, MSSM
Higgs fields can be represented as a triplet in L-R symmetric models (along with neutral and singly-charged Higgs)
L-handed and R-handed Higgs fields are possible
In L-R Symmetric models, the Higgs triplets are only one of the Higgs multiplets that break symmetry between L- and R- handed weak interactions at low energy.
SUSY L-R models suggest low mass for a Doubly Charged Higgs (~100 GeV)
Properties of Doubly Charged Higgs
2
2
,0,
,,
,RL
RL
RLRL
RL
ICHEP04, Beijing, August 16, 20044Sudeshna Banerjee
Doubly-charged Higgs production cross section is enhanced substantially (~35%) due to NLO corrections.
R-handed H++ cross section is smaller by a factor of ~2 due to different value of coupling of these particles to Z bosons.
W-W Fusion :
q
WW H --++q
_
Small probability
|EW - 1| Is small, experimentally observed
+
H++
q W W-q_
Pair Production :
Dominant Production mode
Cross section independent of Fermionic coupling
* H--q
H++q_
Production of H± ±
M. Spira & M. Mühlleitner, hep-ph/0305288
ICHEP04, Beijing, August 16, 20045Sudeshna Banerjee
A typical decay
Couplings like WWH, HHH, HHW and H with hadrons are possible but with very small coupling constants (not considered).
Experimental Signature of H± ± decay
A pair of like sign di-leptons
(Yukawa coupling >10-7)
H--*
q
H++
q_
Decay of H± ±
Contamination from other Standard Model processes is low because of the requirement of two high pT leptons of same sign.
ICHEP04, Beijing, August 16, 20046Sudeshna Banerjee
Z with charge misidentification, probable for high pT tracks
Possible Background Decay Channels
Important modes are those which produce like sign leptons
semileptonic decays bb, t t, Z
Hadronic jets
leptonic decays WZ/ZZ
one electron radiates a photon which then converts to e+e-, check for photon conversion vertices.
W + jets
Cosmic rays eliminated by demanding that the two muons originate at the beam line coincident in time with each other and with a p p collision.
e eZ
eliminated by demanding isolated muons.
ICHEP04, Beijing, August 16, 20047Sudeshna Banerjee
Search Strategy
Choose events triggered with two high pT dileptons.
• electron – energetic EM cluster
• muon – a high pT track matched with a stub in the muon
counter + a MIP trace in the EM calorimeter
Make more stringent selection offline.
Generate signal events in different H±± mass bins covering
the search region.
Generate Monte Carlo samples for different background
decay channels.
Use the same selection criteria on experimental data, signal
and background samples.
If after final selection and background subtraction an excess
is seen in experimental data, a discovery is claimed.
If no excess is seen, a limit on H±± is calculated.
ICHEP04, Beijing, August 16, 20048Sudeshna Banerjee
H±± channel (100 % BR assumed)
Offline selection of events :
Two muons, matched to good tracks (pT> 15 GeV)
Calorimeter ET in outer cone around the muon trace should be small pT of tracks around the muon track should be small
< 2.51 (requirement for events with less than 3 muons)
Two of the muons should have the same charge
Preselection
113 pb-1 integrated luminosity used
113 pb-1 integrated luminosity used
Search performed by DØ experiment
Isolation
Acolinearity
Like sign requirement
Signal Monte Carlo generation (PYTHIA 6.2) Samples with H±± mass ranging from 80 GeV to 200 GeV are generated in steps of 10 GeV
Total signal efficiency for the above selection = 47.5 % ± 2.5 % (not mass dependent)
All efficiencies derived from dataAll efficiencies derived from data
ICHEP04, Beijing, August 16, 20049Sudeshna Banerjee
preselection
preselection + like sign muon requirement
Z events dominate
Effect of Selection criteria (DØ )
b b events dominate
reduces after isolation cut
101 data events
95 b b events
ICHEP04, Beijing, August 16, 200410Sudeshna Banerjee
Final Yield (DØ )
like sign requirement
preselection
isolation
acolinearity
+
+
+
Signal (mass = 100 GeV)
Total background
Data
preselection isolation acolinearity like sign
9.4 8.5 7.5 6.5
5254 ± 47 4113 ± 43 368 ± 14 1.5 ± 0.4
5168 4133 378 3
ICHEP04, Beijing, August 16, 200411Sudeshna Banerjee
Limit calculation depends on mass distribution for signal and background and experimental mass resolution