1. 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

2. Motivation
Higgs pair production has a small Xsection in SM (~33
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

3. Summary of RUN1 results: hh→WWgg
Phys.Rev. D 92, (2015)
hh->wwgg was first proposed by us at :
PLB755(2016)
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.

4. 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.

5. Definition of objs and selections

6. Continuous Background estimation
A number counting analysis is used for the analysis considering low statistics.
Sideband of the di-photon is used to extract
Different control regions are used to validate.
High statistical sideband sample gg+2jets (in lepton requirement) is pragmatically used.

7. Results
The events within /-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.

8. Systematics The most dominant resource of the systematics comes from
the statistical uncertainty of continuum background.

9. Limits 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…

10. 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

11. Other possibility arXiv:1606.01674 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,

12. Schedule for Moriond, 2017 F

13. 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
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)

14. Summary
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 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

15. back up

16. VBF signature Signature : diphoton in central region
two high-pT jets in forward region
VBF pre-selection
N_jet>=2
Δηjj>2
|ηγγ-0.5*(ηj1+ ηj2)|<5