The production of additional bosons and the impact on the Large - PowerPoint PPT Presentation

The production of additional bosons and the impact on the Large Hadron Collider presented by Alan S. Cornell 
 for the HEP group, University of the Witwatersrand With N.Chakrabarty, T .Mandal and 
 B.Mukhopadhyaya (HRI/Uppsala)

Most relevant references • arXiv:1506.00612 • arXiv:1603.01208 • arXiv:1606.01674 • arXiv:1608.03466 • arXiv:1706.02477 • arXiv:1706.06659

Outline • The Effective Lagrangian • Study with Run I data • Formulation of the hypothesis • Compatibility with Run II data • Prediction of signatures at the LHC

Bottom-up approach: What if? g ? g h • Initially we were interested in 
 investigating the Higgs boson 
 transverse momentum • What if the Higgs boson is also being 
 produced in association with something 
 else? • What can we fill the blob with?

The Lagrangian Introducing H and 𝝍 fields with the interactions 
 listed below

Main decay modes of H Decay to single Higgs and 
 Used effective a DM candidate χ coupling • DM is assumed scalar for 
 simplicity H χ • This was our strategy, 
 but we can infer different physics 
 h in the blob h Decay to 
 Z, W ± Decay to 
 double 
 vector boson 
 H H Higgs pair. pairs. h Z, W ⌥

Higgs boson p T spectra Effect of m on Higgs p Spectra X T 2500 Events m =10GeV X m =20GeV X m =30GeV X m =40GeV 2000 X M H =300 GeV m =50GeV 8_10 PT 8_10 PT X Entries 40000 Entries 40000 m =60GeV X Mean Mean 75.01 75.01 m =70GeV X 1500 RMS RMS 33.47 33.47 m =80GeV X s = 13TeV 1000 500 0 20 40 60 80 100 120 140 160 Higgs p (GeV) T

Study of Run I data Category Experiment Result Higgs p T spectra ATLAS h ➝ 𝛿𝛿 and h ➝ ZZ CMS h ➝ 𝛿𝛿 and h ➝ ZZ Di-Higgs resonance ATLAS Limits on H ➝ hh ➝ bb 𝜐𝜐 , 
 Four groups of final states searches 𝛿𝛿 WW , 𝛿𝛿 bb , and bbbb received consideration CMS Limits on H ➝ hh ➝ bb 𝜐𝜐 , 𝛿𝛿 bb , 
 and multi-lepton Top associated ATLAS Limits on h ➝ 𝛿𝛿 Higgs production Measurements on h ➝ bb , and multi-lepton CMS Measurements on h ➝ 𝛿𝛿 , h ➝ bb , and multi-lepton Decays to weak ATLAS Limits on H ➝ ZZ and WW vector bosons CMS Limits on H ➝ ZZ and WW

Satisfactory goodness of the global fit, including Higgs p T

In terms of significance • To see how significant the BSM result is, we use a test pp Collisions @ 7 TeV and 8 TeV 12 2 χ statistic: 𝜓 SM2 - 𝜓 BSM2 − • This gives an SM 10 2 χ improvement on the null 3 σ 8 hypothesis (the Standard Model) in units of sigma 6 • For one degree of 4 2 σ freedom, the best fit point has a 3 sigma 2 improvement. This does 1 σ 0 not mean evidence yet. 260 270 280 290 300 310 320 m [GeV] H

The combined result • Combining all of the 
 2 χ pp Collisions @ 7 TeV and 8 TeV Minimised results produces a 
 32 12 + Best fit: m = 272 GeV − 9 H best fit at 
 31 m H = 272 GeV • The errors are +12 GeV 
 30 and -9 GeV, which are 
 pp H → H h → χ χ one sigma deviations 
 H hh → 29 H VV → pp t t H + t( t )H → from the best fit point H h → χ χ • At this point: H hh → 28 260 270 280 290 300 310 320 m [GeV] Interpret this as H → h+X H BR (H ➝ hh) BR (H ➝ VV) BR (H ➝ h 𝜓𝜓 ) 𝛾 g 0.030 ± 0.037 0.082 ± 0.059 0.89 ± 0.096 1.5 ± 0.6 Close to one degree of freedom, 𝛾 g

The Hypothesis 1. The starting point of the hypothesis is the existence of a boson, H, that contains Higgs-like interactions, with a mass in the range 250-295 GeV 2. In order to avoid large quartic couplings and to incorporate a mediator with Dark Matter a real scalar, S, is introduced. S interacts with the SM: Also decays to SM

The intermediate scalar, S • DM is introduced in the form of a scalar and the decay H → h 𝜓𝜓 via effective quartic couplings • Due to gauge invariance we encounter an awkward situation where a three body decay may be larger or comparable to a two body decay. This can be naturally explained by introducing an intermediate real scalar S Also decays to SM

The Lagrangian Note that some of the effective quartic couplings shown earlier appear here as trilinear. What was formerly a three body decay is now a two body decay (see below).

The Decays of H • In the general case, H can have couplings as those displayed by a Higgs boson in addition to decays involving the intermediate scalar and DM H → WW, ZZ, qq, gg, Z γ , γγ , χχ H → SS, Sh, hh + Dominant decays Diboson decay H → h (+ X ) , S (+ X )

Compatibility with 
 the Run II data 1. hh limits 2. VV spectrum 3. tth → N leptons search 4. Impact on measured Higgs boson cross-sections 5. Higgs boson p T spectrum

σ ( pp → H → hh ) ≈ 600 fb Persistent excess with weak sensitivity to H → hh 
 cross-section because 𝜹𝜹 bb missing. Now CMS has 
 very recently made 𝜹𝜹 bb results (see next slide)

VBF has wide excess. Excess driven by 4e, but also present in 4µ ATLAS-CONF-2017-058

ATLAS-CONF-2017-058

CMS-PAS-HIG-2016-41 Excess of ~20 events 
 in the range 252-272 
 corresponding to 2.5 σ

Top associated Higgs production (Multilepton final state) Can explain 
 µ~2 S/h + h H S/h

Reduced cross-section of ttH+tH is compensated by di-boson, (SS, Sh) decay and large Br(S → WW). Production of same sign leptons, three leptons is enhanced. 
 Enhanced tH cross-section S, h → WW, ττ , ZZ

Table with signal strength w.r.t the SM in the search for tth with multiple leptons

This table includes all data available to data. ATLAS still needs to make available results with most of 2016 data public µ = 1 . 92 ± 0 . 38 Very important to see results with the complete Run 2 data set. Need insight into the kinematics of the leptons and jet activity of these events. 
 (see next slide)

``` µµ CMS-PAS-HIG-17-005 eµ Discrepancy at level of 2.6 σ CMS has made public kinematics of leptons and jets with minimal cuts. The deviation from the SM seems larger than that obtained in the tth search

Impact on measurement of h → WW → 𝓶𝓶 mH = 270 GeV, mh = 125 GeV Because the contamination Unity mS = 140 GeV 0.35 mS = 145 GeV from additional Higgs bosons, mS = 150 GeV mS = 155 GeV 0.3 mS = 160 GeV production from H → Sh comes mS = 165 GeV mS = 170 GeV 0.25 with additional jets (or leptons) 0.2 measurement of signal 0.15 strengths depends on the 0.1 decay. 0.05 In particular: µ γγ ,ZZ 0 0 1 2 3 4 5 6 7 8 9 10 Njet Work in progress with Inclusive > 1 IHEP , Beijing µ W W Contamination 0 j, 1 j Minimum 
 contamination

The survival probability of the H → Sh against a jet veto is model dependent. 
 Here we assume S to be a Higgs-like scalar, for which the survival probability for 0j and 1j is ~10% (assuming Br(S → 𝜓𝜓 )=0). 
 Low MET can also have significant impact on acceptance (under study).

Assuming dominance of H → Sh. 
 With 𝛾 g2 ~2, cross-section at 13 TeV is ~20 pb. Over-measurement of the tth → N lepton and under-measurement of Vh( → bb) and h → WW → ll are a prediction of the model.

Contamination from H → Sh µ = 1 . 92 ± 0 . 38 tth → N lepton searches (SS,3l,4l+b-jets) µ = 1 . 087 ± 0 . 084 Inclusive fiducial cross-section ( 𝜹𝜹 , ZZ → 4 ℓ ) Contamination from H → Sh is ~35% µ = 0 . 8 ± 0 . 1 Vh( → bb) and h → WW →ℓℓ Final states with jet and lepton vetoes The tension between the upper and lower measurements is 2.9 σ . Below we are going to assume that the “true” rate of the SM (SM') is given by the channels with no contamination (i.e. 0.8)

Higgs p T Run II [fb/GeV] [fb/GeV] 2.5 CMS data ATLAS data 1 13.3 fb -1 SM prediction SM prediction γ γ T T γ γ p p /d /d BSM prediction BSM prediction fid fid 2 σ σ SM + BSM SM + BSM 0.8 d d s = 13 TeV s = 13 TeV pp h pp h 1.5 → → γ γ → → γ γ 0.6 m = 265 GeV m = 265 GeV H H m = 135 GeV m = 135 GeV S S 1 BSM: gg H Sh BSM: gg H Sh → → → → 0.4 2 2 = 1.3 = 1.3 β β g g µ = 0.8 µ = 0.8 SM SM 0.5 0.2 0 0 0 50 100 150 200 250 300 350 0 20 40 60 80 100 120 140 160 180 200 γ γ γ γ p [GeV] p [GeV] T T 3 − 10 × [fb/GeV] [fb/GeV] 0.12 90 CMS data ATLAS data 80 SM prediction SM prediction l l 4 T 4 T p p 0.1 /d /d BSM prediction BSM prediction fid fid 70 σ σ SM + BSM SM + BSM d d 0.08 60 s = 13 TeV s = 13 TeV pp h ZZ* 4 l pp h ZZ* 4 l → → → → → → 50 m = 265 GeV m = 265 GeV 0.06 H H m = 135 GeV m = 135 GeV 40 S S BSM: gg H Sh BSM: gg H Sh → → → → 2 2 0.04 30 = 1.3 = 1.3 β β g g µ = 0.8 µ = 0.8 SM SM 20 0.02 10 0 0 0 20 40 60 80 100 120 140 160 180 200 0 20 40 60 80 100 120 140 160 180 200 4 l 4 l p [GeV] p [GeV] T T

Normalising the SM as described in the previous slide. Results correspond to a fit to the four distributions simultaneously. ATLAS h 𝜹𝜹 corresponds to 13.3 fb -1 , 
 while the rest are from the entire 2015-2016 set: χ 2 SM 0 − χ 2 BSM = 3 . 35 σ out of which the choice of normalisation explains 2.2