Higgs Searches at Tevatron Stéphanie Beauceron LPNHE - Paris
Higgs Searches at the Tevatron: Run I
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Transcript of Higgs Searches at the Tevatron: Run I
J. Konigsberg / La Thuile, March 2001
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CDF
D0
Ho
Higgs Searches at the Tevatron: Run I
Introduction The Higgs Run I
SM Higgs (CDF/D0)
ZHo & WHo
MSSM Higgs bbHo,ho,Ao
(CDF)
H+ (CDF/D0)
More beyond Bosophilic (CDF/D0)
Conclusions
Jacobo Konigsberg / Univ. of Florida / CDF
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The Hoiggs: why? where?
[an] EWSB mechanism in SM> Gives mass to particles through H
couplings
> H mass unspecified in SM but couplings are specified
> Mtop, MW and MHiggs related via higher order loops
> Current data points to light HiggsMHiggs < 170 GeV @ 95%,
Osaka’00
> Higgs-like events observed at LEP2 before shutdown:
~114 GeV 95% CL exclusion limit
> The Higgs mass constraints the scale where the SM might break down ()
130<MH<180 GeV/c2 = Mplank
> Possible to discover at Tevatron in the next few years; we’ve started
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“Run I”
4 mile circ. superconducting ring 6x6 proton anti-proton bunches 3.5 us / crossing 1.8 TeV cm energy 1030-1031 inst.luminosity
Oct’92 --------- Feb’96
Run I tot. integrated luminosity: ~ 120-1
pb/detector
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Physics processes @ Tevatron
Zzzz
Looks “interesting”…
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SM Higgs production @ Tevatron
Dominant processes @s=2TeV:
Gluon fusion Higgsstrahlung
Vector boson fusion
)! (QCD ..difficult. toois Hgg mass) inv. met, (lept, y...possibilit a are / HZW
Need much luminosity (x25 ~ top; mH=120)
Larger x-sect with new physics?
tt
lep
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SM Hoiggs decays
lep
For M(H)< ~130 GeV> dominatesbbH
For M(H)> ~130 GeV> contributes
> But cross-sect ¼ of at MH~120 GeV
> Need x100 more Lum ~ t-tbar
WWHbbH
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SM Hoiggs signatures
Standard Model channels M(H) < 130 GeV
Run I searches:
>
>
>
>
bbHWpp 0
bbqqHZWpp 0/
bbHZpp 0
bbHZpp 0
ZH
WH
,e
ee
bb
bb
b-tagging and Mbb resolution are critical for a ligth Higgs
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Tevatron Run I Detectors
Silicon Vertex Detector
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B-tagging in Run I
Displaced vertices (b)~1.5 ps Lxy(b) ~O(mm)
Silicon Vertex Detector (SVX)1 vertex =< 2 tracks Lxy/Lxy > 3.0 Lxy ~ 100µ
(b-tag) ~ 45%/event w/ 2b’s
(b-tag) ~ 0.2%/jetx
y
z
Lxy
bdo
b e,µ (in jets)
Semileptonic b decays
20% ~ BR
20% ~ BR
Xvlcb
Xvlb
(b-tag) ~ 7%/b-jet
(b-tag) ~ 0.5%/jet
(b-tag) ~ 25%/b-jet (~4% c-jet)
(b-tag) ~ 16%/event w/ 2b’s
CDF
CDF/D0
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Run I Mass Resolution
Specific b-jet correctionsCan see bbZ
jjm
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bbWH 0
Event selection:
> High Pt + central Pt(lep)>~20 GeV, Met>20, Pt(j)>15, eta<2
> + b-tags
q
*W0H
b
b
q WBackgrounds:Wbb, tt, WZ, tb
Exp. channelbcknd
dataBr x accept.(90<m(H)<130)
CDF 1 b-tag30 (5)
36 ~ 0.6 – 0.8 %
CDF2 b-tags
3 (1) 6 ~ 0.2 – 0.3 %
D0 1 b-tag25 (3)
27 ‘’
bbm
CDF
D0
bbm
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bbqqHZW '0/
q*/* ZW 0H
q
q
b
b
q ZW / Backgrounds:QCD, tt, Zjj, W/Zbb
Event selection:> Multi-jet trigger: sum(Et)>125 GeV; 4-jets> + 2 b-tags
Pt(b,b)> 50 GeV Need good M(bb) mass resolution
Exp. channelbcknd
dataBr x accept.(90<m(H)<130)
CDF 2 b-tag ~600 589 1.5 – 2.9 %bbm
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bbZH 0
Exp. channelbcknd
dataBr x accept.(90<m(H)<130)
CDF 1 b-tag39 (4)
40 ~ 0.5 – 0.8 %
CDF2 b-tags
4 (1) 4 ~ 0.4 – 0.5 %
bbm
Backgrounds:QCD, Zbb, ZZ, tt, tb
Event selection:> Met > 40 GeV> Veto isolated leptons/tracks> Et(j) > 15 GeV (2 or 3) (Met,j) > 1.0 (j1,j2) < 150o
> + b-tags
q
*0Z
0Z0H
b
b
q
bjm
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bbZH 0
q
*0Z
0Z0H
b
b
q
Backgrounds:Zbb, ZZ, tt, tb
Exp. channelbcknd
dataBr x accept.(90<m(H)<130)
CDF 1 b-tag 3 (1) 5 ~0.2 %
Event selection:> Pt(lep) > 420 GeV> 76<M(l,l)<106 GeV> Pt(j) > 15 GeV, eta<2> Met < 50 GeV (veto top)
> + 1 b-tag
bbm
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Run I Higgs Limits
SM Higgs limits:> Production x Branching Ratio > 95% CL about 30 times higher than SM prediction (for MH~115
GeV) Sets the scale for needed Luminosity, si?
> Best limit from HZbb channel but due to observed data> Expected best channels are: HZbb and HWbbl
cdf
D0
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CDF tagged events
bbpp ,
Higgs “candidate”
bbWWtt ,
Top candidate
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MSSM Higgs Searches
In the MSSM scenario:> Two Higgs doublets lead to 5
Higgs particles: Two neutral CP-even: ho,Ho
One neutral CP-odd: Ao
Two charged: H+ ,H-
> Masses governed by two parameters, for ex:
> Tree level mass relations: M(ho)<M(Zo)<M(Ho) M(Ao) <M(Ho) M(H+)<M(W)
> But M(ho)<~130 GeV after radiative corrections (top,stop etc.)
tan,Am~130 GeV
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MSSM Higgs production @ Tevatron
H/h/A can have SM-like x-sections at small tan
For processes such as HW and HZ
Some production processes such as:Hbb/Hbb/Abb
can have large x-sections
at large tan
SMHgg
WH SM
= h,H,A
)()()(2,,
SM
HAhHbbppbgbbpp
g ~ 1/cos() ~ tan()
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AHh
MSSM Higgs Branching Ratios
For all practical purposes:bb ~ 90%~ 10%
tan
tan
=
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bbbbbbpp
mA
mh
Event selection:
> 4- jets + ET>125 GeV trigger
ET cuts on jets m dependent
3 b-tag (secvtx) bb > 1.9
Backgrounds:QCD, Z/W+jets,tt
Exp. channelbcknd
data
Br x accept.(70<m(H)<300)
CDF 3 b-tag
21 (5)
20 ~ 0.2 – 0.6 %
= h,H,A
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Charged H+iggs Searches
Search directly via:
If then competes with > Depending on tan
btHmmm bHt
Wbt
Search indirectly via lepton disappearance in t-tbar events:• Dilepton & lepton+jet top events suppressed Given t-tbar x-sect & {mH,tan} how likely is it to have observed N events? exclusion regions in {mH,tan}
Regions where
Using hadronic tauidentification: tracking+calorimeterLook in e,mu + tau and in tau+jets+Met channels
tan
Hm
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Charged Higgs Results
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Bosophilic/Fermiophobic Higgs
Some models with two (or more) Higgs doublets predict Ho couplings only to vector bosons, with Hto be dominant for low mass Higgs.
q*/* ZW 0H
q ZW /
x
x
ExpChannel
xxbcknd data
Br x accept.(90<m(H)<130)
CDFe/ + MET
.or. qq6 (2) 6 ???
D0 qq 6 (2) 4 ‘’
Event selection:> Isolated, high-Pt, central,
photons> High-Pt jets/leptons/MET
Backgrounds:Mostly QCD
D0
m
jjm
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Bosophilic Higgs Limits
D0 CDF
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Conclusions
Run I>Searches in all channels for MH < 130 GeV/c2
>No sensitivity to SM Higgs, but we looked anyway> No sign of new physics> Combine results to set limits on xBR>Detectors, backgrounds, taggers understood !>Good experience and baseline for Run II>Sensitivity to neutral MSSM Higgs sector for large tan>Excluded MSSM regions
Run II>Many, many, improvements>We have a chance! (see next talk)