BSM H->hh analyses with ATLAS
detector
方亚泉
高能物理所
院前沿重点项目启动会，暨国际创新海外团队&所创新团队2016年联合年会
IHEP
2016年11月18日
1
Motivation
• Higgs pair production has a small
Xsection in SM (~33 fb@13TeV).
• BSM can effectively enhance Higgs pair
production:
 2HDM, SUSY etc..
• The distribution of pt of Higgs is higher
than expected.
• VBF is the second largest production of
Higgs and has lower theoretical
uncertainty (~5%) and could also probe
new physics
2
Summary of RUN1 results: hh→WWgg
Phys.Rev. D 92, 092004 (2015)
•
hh->wwgg was first proposed by us at :
•
•
PLB755(2016) 509-522
hh->wwgg together with bbgg, bbtautau,bbbb are extensively explored with RUN1 data and
the results are combined
• 2.5s for combined results with 1.8s from wwgg.
3
H->hh->wwgg before ICHEP
(2016)
IHEP Proposed the analysis strategies for this channel aiming at summer results
in January/April in ATLAS HBSM workshops at LAL/Grenoble.
H->hh->4W(l+/-l+/-+jets) started to be proposed and investigated by IHEP group.
An Pheno. paper is under preparation.
4
Definition of objs and selections
5
Continuous Background estimation
6
mwwgg
B
e mww
gg
B
e mww
gg
B
e
B
B
NSR
= NSB mwwBgg emww
gg
1- emgg
B
emww
gg =13.64%
 A number counting analysis is used for the analysis considering low statistics.
B
 Sideband of the di-photon is used to extract e mwwgg
 Different control regions are used to validate.
 High statistical sideband sample gg+2jets (in lepton requirement) is pragmatically used.
Results
The events within 125.07+/-2s GeV mass window are listed in the above table.
The dominant background is still from continuum background.
From the right plot, the statistical fluctuation is still significant.
7
Systematics
The most dominant resource of the systematics comes from
the statistical uncertainty of continuum background.
8
Limits
9
ICHEP: ATLAS-CONF-2016-071
 The selections are mass independent; the differences of the limits are mainly
due to the variations of the signal efficiencies.
 No obvious new signal has been seen:
the deviations between observed limits and expected limits are around 2s.
 More data will tell us the further story…
H->hh searches
after ICHEP
• More people join these
analyses:
– H->hh->W(qq)W*(qq)gg
is being studied.
– H->hh->4W->3lqq, H>hh->4W->4l is also
being investigated.
– Boosted analyses for
high mass.
– Bi-weekly meeting
chaired in ATLAS by
Xiaohu Sun and
Yaquan Fang
10
Other possibility
arXiv:1606.01674
11
S
 Replace one or two h’s with scalar particle s which is not coupled with SM.
 So the s particle is not observed in RUN1 and can be higher than the mass of
Higgs (125 GeV).
 ggWW can have higher contribution than ggbb,
Schedule for Moriond, 2017
F
12
•
•
Plans for Moriond 2017
WWgg paper:
- Title: Search for Higgs boson pair production in the final state of γγWW ∗ using XXX
fb−1 of pp collision data recorded at √s=13 TeV with the ATLAS detector
- Proposed contact editors: Yaquan Fang, Xiaohu Sun, Jason Veatch
- Supporting notes:
 Search for Higgs boson pair production in the final state of yyWW*(->lvqq) using XXX fb-1 of
pp collision data recored at sqrt(s)=13TeV with the ATLAS detector (editors: Qi Li, Xiaohu
Sun)
 Search for Higgs boson pair production in the final state of yyWW*(->qqqq) using XXX fb-1 of
pp collision data recored at sqrt(s)=13TeV with the ATLAS detector (editors: Yu Zhang,
Kai Hessen )
• WWWW paper:
• - Title: Search for Higgs boson pair production in the final state of WW*WW∗ using
XXX fb−1 of pp collision data recorded at √s=13 TeV with the ATLAS detector
- Proposed contact editors: Liang Li, Weiming Yao, Maosen Zhou
- Supporting notes:
•
Search for Higgs boson pair production in the final state of WW*WW*(->l+/-l+/-vvqqqq) using XXX
fb-1 of pp collision data recored at sqrt(s)=13TeV with the ATLAS detector (editors: Yaquan
Fang, Maosen Zhou)
Search for Higgs boson pair production in the final state of WW*WW*(->lllvvvqq) using XXX fb-1
of pp collision data recored at sqrt(s)=13TeV with the ATLAS detector (editors: Jason Veatch,
Xingguo Li)
•
Search for Higgs boson pair production in the final state of WW*WW*(->llllvvvv) using XXX fb-1 of
pp collision data recored at sqrt(s)=13TeV with the ATLAS detector (editors: Debarati Roy,
Yesenia Hernandez)
13
Summary
14
• Conference notes about di-Higgs→w(lν)w(qq)gg are approved
with ATLAS RUN2 data and shown in ICHEP:
– The latter is the only channel available for di-Higgs search in ICHEP in
the mass region smaller than 500 GeV.
– Play a leading role in this analysis.
•
• Editors and contact persons
2 papers, 1 conference note in 2016. Also involved in 750 di-photon, Zgam
analyses.
• Two ATLAS publications are planned for Moriond 2017 for H>hh analyses:
– We play leading roles in these analyses.
– Analyses coordinators and editors
back up
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VBF signature
• Signature :
– diphoton in central region
– two high-pT jets in forward region
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• VBF pre-selection
 N_jet>=2
 Δηjj>2
 |ηγγ-0.5*(ηj1+
ηj2)|<5