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Home , B meson, Scalar boson

Thirteenth Conference on the Intersections of and May 29 – June 3, 2018 Palm Springs, CA

Search for Non Higgs

Ana Elena Dumitriu (IFIN-HH, CPPM), On behalf of the ATLAS Collaboration

5/18/18 1 Introduction and Motivation

● The discovery of the Higgs (125 GeV) by ATLAS and CMS collaborations → great success of and especially Standard Model (SM) ● However.... – MORE ROOM Hierarchy problem FOR HIGGS PHYSICS – Origin of dark , dark energy BEYOND SM – Asymmetry –

– Higgs br to Beyond Standard Model (BSM) of BRBSM < 32% at 95% C.L. ● !!!!!!There is plenty of room for Higgs physics beyond the Standard Model.

● There are several theoretical models with an extended Higgs sector. – 2 Higgs Doublet Models (2HDM). Having two complex scalar SU(2) doublets, they are an effective extension of the SM. In total, 5 different Higgs are predicted: two CP even and one CP odd electrically neutral Higgs bosons, denoted by h, H, and A, respectively, and two charged Higgs bosons, H±. The parameters used to describe a 2HDM are the masses and the ratios of their vacuum expectation values. ● type I, where one SU(2) doublet gives masses to all and and the other doublet essentially decouples from ● type II, where one doublet gives mass to up-like quarks (and potentially ) and the down-type quarks and leptons receive mass from the other doublet. – (SUSY), which brings along super-partners of the SM particles. The Minimal Supersymmetric Standard Model (MSSM), whose Higgs sector is equivalent to the one of a constrained 2HDM of type II and the next-to MSSM (NMSSM) are among the experimentally best tested models, because they provide good benchmarks for SUSY. – General searches – Invisible decaying Higgs boson 2 Search for doubly-charged scalar bosons decaying to same-sign W bosons HIGG-2016-09: Phenomenology

● The scalar sector of the Standard Model is one of the main candidates to host new particles and forces beyond the SM

● A variant of such an extension: a hypercharge Y = 2 scalar triplet, ∆, complements the SM scalar doublet H.

● The renormalizable scalar potential V(H, ∆) is defined in its most general form by: Pair production (done in Rel 20.7): pp →γ*,Z* → H±±H∓∓ Associated production: pp → W*+ → H±±H∓ Single production: pp → W±*W±* → H±± (proportional to vt, negligible)

● Benchmark points considered: mH±± ranging from 200 − 700 GeV in steps of 100 GeV

● As in all analysis:

– SR: 3 channels considered, optimized using TMVA CutsSA

● Dominant backgrounds:

– 2Lss : WW , WZ, Vγ contribute to the prompt sources; Z+jets, tt contribute to fake backgrounds; +QmisID from W ±W ∓ and Z+jets.

– 3L: WZ, ZZ, Vγ, ttV contribute to prompt backgrounds.; Z+jets and tt contribute to fakes. ; No QmisID.

– 4L: ZZ and tt Z contribute to prompt sources; Fakes originate from Z+jets and tt .

● Prompt sources are estimated from MC.

● Fake estimation:

– 2Lss and 3L: Data-driven fake factor method is used (FF)

– 4L: using MC, with corrections applied based on MC-data agreement in the control regions. 3 Search for doubly-charged scalar bosons decaying to same-sign W bosons HIGG-2016-09: Results

mH++ = 200 GeV

● A search for the pair production of doubly charged Higgs is performed through the selection of multi- events with MET + jets.

● No significant excess is observed in data. Combining those channels, the model is excluded at 95% C.L. for masses of up to approximately 239 GeV.

● Further steps: – Perform the analysis with the two AP and PP production modes – Optimize the SR definition, fake estimation – Use of the ttH analysis synergy and derived data set – Goal: Increase drastically the observed limit (>300GeV) with PP+AP production mode @ 80fb-1 4 Search for doubly charged Higgs boson production in multi-lepton final states, 36.1 fb-1 (link)

● This analysis focuses on BSM theories that contain a doubly charged Higgs particle H±± using the observed of same-charge lepton pairs. The analysis targets only decays of the H particle into and , denoted by ℓ (with 2,3,4-lepton SR) + further divided into unique flavour categories (e or μ) to increase the sensitivity.

● Doubly charged Higgs bosons can arise in a large variety of BSM theories, namely in left-right symmetric (LRS) models, Higgs triplet models, the little Higgs model, type-II see-saw models, the Georgi–Machacek model, scalar singlet dark matter, and the Zee–Babu mass model.

● No significant excess above the Standard Model prediction was found → lower limits are set on the mass of doubly-charged Higgs bosons:

±± ±± ± ± ±± ± ± – 770 GeV and 870 GeV for the H L mass and for B(H →ℓ ℓ ) = 100% and >450 GeV for B(H →ℓ ℓ )≥10% for any combination of partial branching ratios.

±± ±± ± ± ±± ± ± – on the H R mass vary from 660 GeV to 760 GeV for B(H → ℓ ℓ ) = 100% and are above 320 GeV for B(B(H → ℓ ℓ )≥10% ● The observed limits are consistent with the expected limits.

5 Search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a Z boson (link)

● -3 The Higgs boson (H→ZZ→ νννν) has a branching ratio BH→inv of 1.06x10 for mH = 125 GeV, a larger

BH→inv can exist in many extensions of the SM (a Higgs boson can decay to light , graviscalars in extra-dimension models, Majorons, neutrinos, or dark matter (DM) through the Higgs portal model).

● Observation of a BH→inv significantly above the SM value would give a strong indication for physics BSM.

● Moreover, models with a sizable BH→inv often involve a Higgs boson decaying into WIMPs.

● miss The search is carried out in the ℓℓ + E T final state, no significant data excess above the expectation of the SM backgrounds.

● An observed (expected) upper limit of 67% (39%) is set on BH→inv at

the 95% CL for mH = 125 GeV [75% (62%) derived in the same final state using the ATLAS data √s= 7 and 8 TeV] ● The corresponding observed (expected) limit on the production cs of the ZH process with prompt Z→ ee and Z → μμ decays and invisible Higgs boson decays is 40 (23) fb at the 95% CL. ● Exclusion limits are placed on masses in a simplified dark matter

model with an axial-vector mediator and fermionic WIMPs: mmed is excluded up to 560 GeV at the 95% CL for a light WIMP, while the

WIMP mass m is excluded up to 130 GeV for mmed = 400 GeV.

6 Search for additional heavy neutral Higgs and gauge bosons in the ditau final state produced (link)

● Heavy Z' gauge bosons appear in many extensions of the SM. In particular, models in which the Z' boson couples preferentially to third-generation fermions may be linked to the high mass of the top or to recent indications of lepton flavour universality violation in semi-tauonic B decays. ● Search for neutral MSSM Higgs bosons as well as high-mass Z' resonances in the ditau decay mode, in the lephad and hadhad decay modes (lep represents the decay of a τ-lepton to an or a and neutrinos, had represents the decay to one or more and a neutrino).

● Narrow resonances with masses of 0.2–2.25 TeV and tanβ of 1–58 for the MSSM Higgs bosons.

● No indication of an excess over the expected SM background is found, upper limits on the cross section for the production of scalar and Z' bosons times the branching fraction to ditau final states are set at 95% CL: 0.78–0.0058 pb (0.70–0.0037 pb) for –gluon fusion (b-associated) production of scalar bosons with masses of 0.2–2.25 TeV and 1.56–0.0072 pb for Drell–Yan production of Z0 bosons with masses of 0.2– 4 TeV.

● In the context of the hMSSM scenario, the most stringent limits for the combined search exclude tanβ> 1.0 for mA =

0.25 TeV and tanβ> 42 for mA = 1.5 TeV at 95% CL.

● In the context of the Sequential Standard Model, Z'SSM bosons with masses less than 2.42 TeV are excluded at 95% 2 7 CL, while mZ'NU < 2.25–2.60 TeV is excluded in the range 0.03 < sin φ < 0.5 in the non-universal G(221) model. Search for Higgs boson decays to beyond-the- Standard-Model light bosons in four-lepton (link)

● Exotic Higgs boson decays have been proposed as a way to search for evidence of new physics → the addition of even a small coupling to a new light state could open up sizeable new decay modes. In addition, new particles may couple preferentially to the Higgs boson since it provides a possible “portal” for hidden-sector particles to interact with SM particles. ● The processes under study here are referred to as pp → H → ZX/XX → 4ℓ, with Z being the SM Z boson and with X representing

a possible new Zd or a new pseudoscalar boson a; same-flavour decays of the new particle to pairs of electrons and muons are considered. ● Two well-motivated benchmark models that predict exotic decays to light beyond-the-Standard-Model (BSM) bosons:

– higher mass range: the SM is extended with a dark-sector U(1) group, denoted U(1)d, leading to the appearance of a BSM

vector boson, Zd. – lower mass range: two Higgs doublets and an additional singlet scalar field (2HDM+S). This leads to the appearance of a BSM

pseudoscalar boson, a. The Zd boson and the a pseudoscalar could each comprise the intermediate state in the decays H → ZX → 4ℓ and H → XX → 4ℓ.

● The search targeting the ZX intermediate state is sensitive to Zd masses between 15 and 55 GeV, and the search targeting

the XX intermediate state is sensitive to Zd masses between 15 and 60 GeV. Intermediate states of XX (X = a or Zd) where

the boson mass mX is between 1 and 15 GeV (excluding masses near known dilepton resonances from states) are searched for in events with four muons.

● The data are found to be globally consistent with SM background predictions. Upper limits are set on the branching ratio of Higgs boson to ZZd, ZdZd, and aa, corresponding to B(H→ZZd) ≈ 0.1%, B(H→ZdZd) ≈ 0.01%, and B(H→aa) ≈ 1% 8 respectively (depending on mass range). Search for Higgs boson decays into pairs of light (pseudo)scalar particles in the γγjj final state (link)

● Many BSM models predict exotic decays of the Higgs boson. One possibility is that the Higgs boson decays into a pair of new (pseudo)scalar particles, a, which in turn decay to γγjj, selecting events where vector-boson fusion (VBF) is the dominant Higgs boson production mode; an excellent unexplored final state for probing these -suppressed coupling models.

● H→γγjj final state is more sensitive to couplings with the new physics sector similar to the photon coupling to the SM Higgs boson, while the H→γγγγ final state is more sensitive to scenarios with enhanced photon couplings.

● The search for H → aa →γγ gg is performed in the mass range 20 < ma < 60 GeV and with additional jet requirements to enhance VBF-produced signal while suppressing the +jets background.

● No significant excess of data is observed relative to the SM predictions.

● An upper limit is set for the product of the production cross- section for pp → H and the branching ratio for the decay H → aa →γγ gg. The upper limit ranges from 3.1 pb to 9.0 pb depending

on ma, and is mostly driven by the statistical uncertainties.

9 Search for heavy ZZ resonances in the ℓ+ℓ−ℓ+ℓ− and ℓ+ℓ−νν final states (link)

● Two searches for a heavy resonance decaying into two SM Z bosons, encompassing the final states ZZ → ℓ+ℓ−ℓ+ℓ− and ZZ → ℓ+ℓ−νν, the results are interpreted separately for the ggF and VBF production modes.

● These searches look for an excess in distributions of the four-lepton invariant mass, m4ℓ, for the ℓ+ℓ−ℓ+ℓ− final state, + − and the transverse invariant mass, mT, for the ℓ ℓ νν final state, as the escaping neutrinos do not allow the full reconstruction of the final state.

● No excess → limits on the production rate of different signal hypotheses; The first hypothesis is the ggF and VBF production of a heavy Higgs boson (-0 resonance) under the narrow-width approximation (NWA). The upper limits on the production rate of a heavy Higgs boson are then translated into exclusion contours in the context of the two-Higgs-doublet model. As several theoretical models favour non-negligible natural widths, large-width assumption (LWA) models, assuming widths of 1%, 5% and 10% of the resonance mass, are also studied. The interference between the heavy scalar and the SM Higgs boson as well as between the heavy scalar and the gg → ZZ continuum background are taken into account in this study. Limits are also set on the Randall–Sundrum (RS) model with a warped extra dimension giving rise to a spin-2 Kaluza–Klein (KK) excitation of the GKK.

10 ● The results of the search are interpreted as upper llimits on the production cross section of a spin-0 or spin-2 resonance. ● The mass range of the hypothetical resonances considered is between 200 GeV and 2000 GeV depending on the final state and the model considered.

● Combining the two final states, 95% CL upper limits range from 0.68 pb at mH

= 242 GeV to 11 fb at mH = 1200 GeV for the gluon–gluon fusion production

mode and from 0.41 pb at mH = 236 GeV to 13 fb at mH = 1200 GeV for the vector-boson fusion production mode. ● The results are also interpreted in the context of Type-I and Type-II two- Higgs-doublet models, with exclusion contours given in the tan β versus

cos(β − α) (for mH = 200 GeV) and tan β versus mH planes.

● This mH value is chosen so that the assumption of a narrow Higgs boson is valid over most of the parameter space and the experimental sensitivity is maximal. ● The limits on the production rate of a large-width scalar are obtained for widths of 1%, 5% and 10% of the mass of the resonance, with the interference between the heavy scalar and the SM Higgs boson as well as the heavy scalar and the gg → ZZ continuum taken into account. ● In the framework of the Randall–Sundrum model with one warped extra dimension a graviton excitation spin-2 resonance with m(GKK) < 1300 GeV is excluded at 95% CL. 11 Search for heavy resonances decaying into a W or Z boson and a Higgs boson in final states with leptons and b-jets (link)

● Aim: – search for the production of new heavy vector bosons (W' and Z'), that decay into a W or a Z boson and an h boson – search for a heavy CP-odd A that decays into a Z and an h boson.

● The analyses target leptonic decays of the vector bosons and decays of the h boson into a b-quark pair: W'' → W±h → ℓ±νbb, Z'/A →Zh → ℓ+ℓ-bb, , Z'/A →Zh → ννbb – Two benchmark models are used in this analysis:

● Model A, the branching fractions to fermions and gauge bosons are comparable, as in some models with an extended gauge symmetry ● Model B, fermionic couplings are suppressed, as in strong dynamical models such as the minimal composite Higgs model. At low resonance masses and large gV couplings, the HVT models fail to reproduce the SM parameters, thus this search focuses on high masses, from 500 GeV up to 5 TeV.

● The results from the A → Zh search are interpreted as exclusion limits on the ratio of the vacuum expectation values of the two Higgs doublets, tan(β), and on cos(β-α), where α is the mixing angle between the two CP-even Higgs bosons. The exclusion limits are evaluated for the Type I, Type II, Lepton-specific, and Flipped 2HDMs. This search starts at the Zh threshold of approximately 220 GeV and goes up to 2 TeV.

12 ● No significant excess of events is observed above the SM predictions in all three channels.

● Upper limits are placed at the 95% CL on the cross-section times branching fraction, (pp →V'→Vh) B(h→bb; cc), ranging between 1.1x10-3 and 2.8x10-3 pb for the W' boson and between 9.0x10-3 and 1.3x10-3 pb for the Z' boson in the mass range of 500 GeV to 5 TeV.

● The W' and Z' bosons with masses mW' < 2.67 TeV (2.82 TeV) and mZ' < 2.65 TeV (2.83 TeV) are excluded for the benchmark HVT Model A (Model B), while for the combined HVT search masses up to 2.80 TeV (2.93 TeV) are excluded.

● -3 -1 For an A boson, upper limits are placed on (pp→A→Zh)xB(h→bb) between 5.5x10 and 2.4x10 pb for gluon–gluon fusion production and 13 between 3.4x10-3 and 7.3x10-1 pb for production with associated b-quarks in the mass range 220 GeV to 2 TeV. Search for WW=WZ resonance production in ℓℓqq final states (link)

● Search for a charged or neutral resonance, in a mass range from 300 GeV to 5000 GeV, that decays into a WZ or WW boson pair, W boson decays leptonically and the other W=Z boson (V) decays hadronically. The spectrum of the

reconstructed invariant mass of the WV resonance candidates, m(WV), is examined for localized excesses over the expected SM background.

● For high-mass resonances, the opening angles between the quarks from V boson decays are small and both quarks can be identified as a single jet → merged analysis(ℓνJ). In contrast, separate identification of the two quarks from low-mass resonances → resolved analysis (ℓνjj).

● Three signal models are used to optimize the event selection: an additional heavy Higgs boson predicted by many theories beyond the SM, a heavy vector triplet (HVT) parameterization based on a simplified phenomenological Lagrangian and a bulk Randall–Sundrum (RS) model.

● The data are compatible with the Standard Model background hypothesis and the largest local excess observed is approximately 2.7 , not significant.

● Two different production modes are considered, the vector-boson fusion and the gluon–gluon fusion or quark–antiquark annihilation, and independent limits are set. Masses below 2730 GeV and 3000 GeV are excluded at 95% CL for the Z' in models A and B of the HVT parametrization, respectively. For the W' resonance, the corresponding limits obtained exclude masses below 2800 GeV and 299014 GeV. Additionally, RSGKK signals with k= MPl = 1.0 produced via gluon–gluon fusion are excluded at 95% CL below 1750 GeV. Search for Neutral MSSM Higgs bosons H/A and Z'

decaying to τℓτh (link)

● Z' bosons often arise in grand unified theories, offering an explanation for the high mass of the top-quark, Strong Flavour Model (SFM) . Non-universal Z' models can also explain the anomalous dimuon production observed at the D0 and the excess in semileptonic B-meson decays into leptons observed at the Belle and BaBar experiments

● Searches in the ditau channel are also sensitive to sgoldstino-like scalars in supersymmetric models, hidden sector Z' models and to the anomalous -lepton dipole moments and higher order -gluon couplings

● The Sequential Standard Model (SSM) contains a single additional Z' boson with the same couplings as the SM Z boson, and while not theoretically well motivated, serves as a benchmark.

● The results of a search for a neutralMSSMHiggs boson are presented as well as high-mass resonance decaying into two leptons. Tau leptons can decay into a charged lepton and two neutrinos, or hadronically (had), predominantly into one or three charged , a neutrino and often additional neutral pions.

● The results of the search are interpreted in various MSSM scenarios. The impact on the signal acceptance from altering Z' couplings is evaluated and limits are also placed on a particular model that exhibits enhanced couplings to tau-leptons.

● The exclusion limits are calculated in dependence of Higgs mass and the relative magnitude of the production processes (gluon fusion and b-associated production). ● Using the MSSM prediction of this fraction of the production cross sections,

these limits can be expressed in dependence of mA and tanβ . ● The cross section limit combination is shown in left and the combination of the15 MSSM limits are shown above. Search for the Higgs boson produced in association with a vector boson and decaying to two spin-zero particles in the H → aa → 4b channel channel (link)

● The Higgs boson has been proposed as a possible “portal” for hidden-sector particles to interact with SM particles.

● If the a boson mixes with the Higgs boson and inherits its Yukawa couplings, decays

of the type a → bb are expected to be dominant for ma > 2mb. These kinds of models have been used to explain the observations of a gamma-ray excess from the galactic center by the Fermi Large Area Telescope (FermiLAT). In models of

neutral naturalness, the a boson could have mean proper lifetimes (cτa) ranging from about 10m up to O(km)]. Lifetimes much smaller than 10m are referred to as “prompt”.

● This search focuses on the WH and ZH processes, with W →ℓν and Z →ℓℓ and H → aa → 4b. The a boson can be either a scalar or a pseudoscalar under transformations (decay mode not sensitive to the

difference in coupling). The a-boson signals considered have masses in the range 20 GeV < ma < 60 GeV and mean proper lifetimes ca up to 6 mm.

● The search for H → aa → 4b is performed in the mass range 20 GeV ma 60 GeV, considering both prompt and long-lived a bosons with mean proper lifetimes up to 6 mm. The analysis uses several kinematic variables combined in a multivariate discriminant in signal regions and uses control regions to reduce the uncertainties in the backgrounds.

● No significant excess of data is observed relative to the SM predictions.

● Upper limits at 95% CL are derived for the WH and ZH production cross-section times branching ratio of the decay H → aa → 4b.

● The combined/observed upper limit for promptly-decaying a bosons

ranges from 3.0 pb for ma = 20 GeV to 1.3 pb for ma = 60 GeV, assuming that the ratio of WH and ZH cross-sections follows the SM prediction.

● For a bosons with longer proper lifetimes, the best limits are 1.8 pb and

0.68 pb, for ma = 20 GeV and 60 GeV respectively, at ca cτa = 0.4 mm. 16 Conclusion and Future Prospects

● ATLAS is very active in searching for BSM phenomena in the Higgs sector: https://twiki.cern.ch/twiki/bin/view/AtlasPublic

● No sign of additional Higgs boson seen in the LHC data.

● However, exclusion limits continue to improve and limit model phase space.

● Hope for the HBSM evidence in Run II (Total integrated luminosity for Run II ~ 150 fb-1), and beyond at the HL-LHC (3000 fb-1).

17 Backup Slides

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