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Search for Higgs Boson Decays to a Meson and a Photon

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Search for Higgs Boson Decays to a Meson and a Photon Search for Higgs boson decays to a meson and a photon Konstantinos Nikolopoulos University of Birmingham on behalf of the ATLAS and CMS Collaborations Precision Workshop - Rencontres du Vietnam ATLAS experiment at CERN 26 September 2016, Quy Nhon, Vietnam This project has received funding from the European Union’s 7th Framework Programme for research, technological development and demonstration under grant agreement no 334034 (EWSB) Higgs Mechanism: Scalar Couplings Structure Higgs-fermion interactions: YukawaBosonic sector:couplings + V EWSB gives mass to W , W −, Z bosons H • Higgs interactions to vector bosons: defined by symmetryHiggs breaking couplings proportional to m2 gHV V • W /Z Higgs interactions to fermions: ad-hoc hierarchical Yukawa couplings∝mf 2m2 g = V V HVV v Higgs Mechanism: Scalar Couplings Structure Fermionic sector: Bosonic sector: f + V EWSB gives mass to W , W −, Z bosons H After introducting Higgs field, can add • H • Higgs couplings proportional to m2 gHV V gHff¯ Yukawa terms to Lagrangian • W /Z 2 m Higgs couplings proportional to fermion mass 2 2mV f • 2mV ghV V = V ghff¯ = f¯ gHVV = υ υ mf v gHf f¯ = Yf = v Fermionic sector: v is Higgs field vacuum expectation value f • After introducting Higgs field, can add Loops (e.g. γ,gluon)sensitivetoBSMphysics H • Yukawa couplings not imposed• by fundamental principle gHff¯ Yukawa terms to Lagrangian Higgs couplings Enhanced proportional Yukawa to fermion couplings mass in BSM scenarios • 4of39 ¯ [Phys. Rev. D80, 076002, Phys. Lett. B665 (2008) 79, Phys.Rev. D90 (2014) 115022,…] f mf Unitarityg ¯ = Y = bounds (through EFT) for fermion mass Hf f f v generation scale (1st/2nd generation) v is Higgs field vacuum expectation value • Loops (e.g. γ,gluon)sensitivetoBSMphysics • υ3 ⇤ <20 TeV 4of39 ⇠ smf [Phys. Rev. Lett. 59, 2405 (1987); Phys.Rev. D71 (2005) 093009] K. Nikolopoulos / Quy Nhon, 26 Sep 2016 / Search for Higgs boson decays to a meson and a photon 2 Higgs-fermion interactions: The story so far 4.5(3.4)σ ATLAS-CONF-2015-044 JHEP 1504 (2015) 117 Progress in Higgs boson properties: mass known to 0.19% bosonic decays measured to ~20-30% In fermion sector, different picture: 3.2(3.5)σ τ-lepton: direct evidence by ATLAS and CMS for h→ττ e,µ: no evidence→non-universality t-quark: no firm evidence for ttH; indirect evidence b-quark: no evidence for h→bb in LHC; mild excesses c-quark: no direct evidence, loose bounds from h→bb u/d/s-quarks: no direct searches available JHEP 1405 (2014) 104 K. Nikolopoulos / Quy Nhon, 26 Sep 2016 / Search for Higgs boson decays to a meson and a photon 3 We take m =125.9 0.4 GeV, and we obtain Γ(H γγ)=9.565 10−6 GeV from H ± → × the values of the Higgs-boson total width and branching fraction to γγ in Refs. [11, 12]. We estimate the uncertainties in the indirect amplitude along the lines that were suggested in footnote 2 of Ref. [8]. In Γ(H γγ), we take the uncertainty from uncalculated higher- → order corrections to be 1%, and the uncertainties that arise from the uncertainties in the top-quark mass mt and the W -boson mass mW to be 0.022% and 0.024%, respectively. We take the uncertainties in theExclusive leptonic decay widths Decays to be 2.5% for h the→J/ψQandγ 1.3% for h→Qγ decays:the a Υclean. We probe estimate on the Yukawa uncertainties couplings in the of indirect 1st and amplitude 2nd generation from uncalculated quarks mass Q is a vector meson or quarkonium2 2 state corrections to be mV /mH . We have not included the effects of the uncertainty in mH , as it Two contributions: direct and indirect amplitude is expected that that uncertainty will be significantly reduced in Run II of the LHC. Direct amplitude: provides sensitivity to Yukawa couplings The uncertainties in the direct amplitude arise primarily from the uncertainties in φ0, Indirect amplitude: larger contribution than direct amplitude 0 2 FIG. 1: The Feynman diagrams2 for the direct amplitude2 for H V + γ4 at order αs.Theshaded Destructive interferencev , and uncalculated corrections of order αs,orderαsv ,andorder→ v . We estimate the ⟨ ⟩ blob represents the quarkonium wave function. The momenta that are adjacent to the heavy-quark order-α2 correction to be 2%, the order-α v2 correction to be 5% for the J/ψ and 1.5% for s “Direct” contributionlines are defined in the text.s “Indirect” contribution the Υ,andtheorder-v4 correction to be 9% for the J/ψ and 1% for the Υ. The uncertainties Small angular separation of decay products in the direct amplitude that arise from the uncertainties in mc and mb are 0.6% in the case of the J/ψ and 0.1% in the case of the Υ, and so they are negligible in comparison withthe other uncertainties in the direct amplitude. Our results for the widths are7 meson decay 2 −10 Γ(H J/ψ + γ)= (11.9 0.2) (1.04 0.14)κc 10 GeV, (53a) products → FIG. 2: The Feynman± diagram− for the indirect± amplitude for×H V + γ.Thehatchedcircle Phys.Rev.2 →D90 (2014) 11, 113010 Higgs Γ[H Υ(1S)+γ]=!(3.33 0.03) (3.49 0.15)κ! 10−10 GeV, (53b) → represents top-quark! ± or W -boson− loops, and± the shaded!b blob× represents the quarkonium wave function. ExclusiveΓ[H Υ decays(2S)+γ ]=lead!(2 to.18 distinct0.03) experimental(2.48 0.11)κ !2 signatures10−10 GeV, (53c) → ! ± − ± b! × In the direct process, the Higgs boson decays into a heavy quark-antiquark (QQ¯) pair, photon High-pT isolated •quarkonium recoiling against 2 −10 Γ[H Υ(3S)+γ]=!(1.83 0.02) (2.15 0.10)κb! 10 GeV. (53d) high-pT→ isolated photonone of! which radiates± a photon− before± forming a quarkonium! × with the other element of the! pair. ! The SM values for the widths (κQ! =1)are ! K. Nikolopoulos / Quy Nhon, 26 Sep 2016 / Search for Higgs bosonIn the decaysindirect to process a meson, the Higgs and bosona photon decays through a top-quark loop or a vector-4 • ∗ ∗ boson loop to a γ and a γ (virtual+0.05 photon).− The8 γ then decays into a vector quarko- ΓSM(H J/ψ + γ)=1.17−0.05 10 GeV, (54a) nium.→ × Γ [H Υ(1S)+γ]=2.56+7.30 10−12 GeV, (54b) SMThe Feynman→ diagrams for the direct−2.56 and× indirect processes are shown in Figs. 1 and 2, Γ respectively.[H Υ(2 ItS is)+ the quantumγ]=8 interference.46+7.79 between10−12 theseGeV two, processes that provides phase(54c) SM → −5.35 × 3 Γ [H Υ(3S)+γ]=10.25+7.33 10−12 GeV. (54d) SM → −5.45 × 7 We do not include results for the ψ(2S) because a value for v2 [ψ(2S)] does not exist in the literature ⟨ ⟩ and because it is likely that v2 for the ψ(2S) is so large that the theoretical uncertainties in the width would be very large. 18 and κb ∆Υ(1S) = (0.948 0.040) + i(0.130 0.019) eff +0.0184 0.0015i, ± ± κγγ − ! " κb ∆Υ(2S) = (1.014 0.054) + i(0.141 0.022) eff +0.0207 0.0015i, (43) ± ± κγγ − # $ κb ∆Υ(3S) = (1.052 0.060) + i(0.148 0.025) eff +0.0221 0.0015i. ± ± κγγ − ! " Approximate expressions forκ ¯ρ0 ,¯κω andκ ¯φ have been given in (22) and (23). The constant terms in the above results show the tiny power-suppressed corrections. Only for the Υ(nS) states they reach the level of percent. Our complete expressionsfortheCP-oddcoefficients ∆˜ V are also given in Appendix E. It is a good approximation to only keep the direct contributions in these terms, which are likely to give rise to the dominant effects. Their coefficients are the same as in the expressions above, but withκ ¯q replaced by κ˜¯q and κb replaced byκ ˜b. It is interesting to compare our result for the quantities ∆V with corresponding expressions obtained by other authors. From [10] one can extract ∆ρ0 =(0.095 0.020) (2¯κu +¯κd)/3, ∆ =(0.092 0.021) (2¯κ +¯κ )and∆ =(0.130 0.027)¯κ , while from± [32] one can obtain ω ± u d φ ± s ∆ =(0.392 0.053)¯κ , ∆ =(1.048 0.046)κ , ∆ =(1.138 0.053)κ and ∆ = J/ψ ± c Υ(1S) ± b Υ(2S) ± b Υ(3S) (1.175 0.056)κb. These values are systematically higher than ours due to the fact that these authors± have not (or not fully) included QCD radiative corrections and RG evolution effects in the direct contributions. For the Υ(nS) states it is important to keep the small imaginary parts of the direct contributions, since in theExclusive SM the real parts alm Decaysost perfectly cancel h→ inQ theγ combinations 1 ∆V in (37). The result for ∆ω obtained in [10] misses the contribution from ω φ mixing and− contains a sign mistake in front ofκ ¯ . Note also that our predictions for the Substantial− recent% interest% from the theory communityd regarding branching ratio estimatesvector∆V parameters mesons, and we %feasibility: of find light% mesons are significantly more accurate than those obtained in [10]. 6 Br(h J/ψγ)=(2.95 0.07f 0.06direct 0.14h γγ) 10− , → ± J/ψ ± ± → · 4Phenomenologicalresults+1.75 9 Br(h Υ(1S) γ)=(4.61 0.06fΥ(1S) 1.21 direct 0.22h γγ) 10− , → ± − ± → · (45) We begin by quoting our benchmark results for the+0.75h V γ branching fractions9 in the SM.
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