Adam Falkowski LPT Orsay Exotic and CP violating Higgs Decays Grenoble, 02 July 2014 Based on work with Roberto Vega-Morales 1405.1095, and with Yi Chen, Ian Low, Roberto Vega-Morales, 1405.6723
Plan Intro: Higgs: where do we stand? Part 1: Exotic Higgs decays to hidden photon in 4-lepton channel Part 2: New CP violating observables in Higgs decays
Higgs: where do we stand
Where do we stand Gazillion sigma evidence for a SM- like Higgs boson Higgs mass is 125.5 GeV, give or take a couple hundred MeV. Evidence for coupling both to SM gauge bosons and to fermions Evidence for gluon fusion and vector boson fusion production
Simplified Effective Higgs Lagrangian Simpler effective theory with 7 free parameters <ALL> these parameters are meaningfully constrained by current Higgs data Standard Model limit: c V =c f =1, c gg =c γγ =c Z γ =0
7 parameter fit using only Higgs data: Belusca-Maito, AA arXiv: 1311.1113 + updates Best fit and 68% CL range for parameters (warning, some errors very non-Gaussian) Islands of good fit with negative cu, cd, cl ignored here ∆χ 2 = χ 2SM - χ 2min ≈ 5.5, with 7 d.o.f. SM hypothesis is a perfect fit :-(((
Where do we stand Higgs is obnoxiously SM-like Dimension-6 operators contributing to Higgs couplings suppressed by the scale Λ of order < 1 TeV at most c.f. with EWPT probing Λ∼ 10 TeV, or B physics probing Λ∼ 100 TeV, or Kaon physics probing Λ∼ 10000 TeV NP reach will improve in the next LHC run, but not so much in terms of Λ However, there is plenty of room for exotic decays not predicted by the SM
Limits on exotic Higgs branching fraction Assuming Higgs couplings to SM fixed Br exotic @ % D 10 15 20 25 10 σ (Higgs) uncertainty 8 ignored 99 % 99 % 6 σ (gg → Higgs) Dc 2 uncertainty included 95 % 95 % 4 2 0 0.0 0.1 0.2 0.3 0.4 dG h ê G h ,SM Br(h → exotic) ≲ 18% at 95% CL
Limits on exotic Higgs branching fraction Allowing some Higgs couplings to SM to float Br exotic @ % D 10 20 30 40 Higgs coupling Higgs couplings 8 to bees floating to SM fixed 99 % 99 % Higgs coupling 6 to gluons floating Dc 2 95 % 95 % 4 2 0 0.0 0.2 0.4 0.6 0.8 dG h ê G h ,SM Br(h → exotic) ≲ 30% at 95% CL
Constraints on additional width - If all couplings at SM value, exotic branching fraction larger than 18% disfavored at 95% CL - Allowing new exotic width and, simultaneously, new contributions to Higgs couplings to SM gives even more wiggle room, typically up to 30% exotic branching fraction - Direct limit on Higgs width from CMS: Γ < 4.2 Γ SM @ 95% CL implying exotic branching fractions up to 80%
Exotic Higgs Decays - Why? 18% exotic Higgs branching fraction means that the LHC cross section for exotic Higgs decays could easily be order picobarn The SM Higgs width is just 4 MeV, so even weakly coupled new physics can lead to a significant branching fraction for exotic decays. E.g., a new scalar X coupled as c|H|^2 |X|^2 corresponds to BR(h � X*X)=10% BR for c~0.01. Thanks to the large Higgs cross section even tiny exotic branching fractions may possibly be probed. For spectacular enough signatures we can probe BR ∼ O(10^-5) now and BR ∼ O(10^-9) in the asymptotic future. [ Note that the Higgs was first discovered in the diphoton (BR~10^-3) and 4-lepton (BR~10^-4) channels]
Exotic Higgs Decays This talk: AA,Vega-Morales, 1405.1095 Exotic Higgs decays in the golden channel in the hidden photon model For much more see the Snowmass review Curtin et al, 1312.4992
Hidden Photon in the golden channel
Hidden photon model Model with a new light exotic gauge boson decaying to leptons Originally motivated by astrophysical anomalies (PAMELA/FERMI/AMS cosmic ray positron excess) Now, a popular benchmark model for hidden sector searches
Hidden photon model Hidden photon X talking to SM vie hypercharge portal L = L SM � 1 � ✏ 2 cos − 2 ✓ W X µ ν + 1 ✏ X µ ν ˆ ˆ X ˆ X µ ˆ B µ ν ˆ m 2 2 ˆ X µ + X µ ν 4 2 cos ✓ W One consequence of mixing: hidden photon couples to matter 1 � tan 2 ✓ W m 2 m 2 ✓ ◆ � X + T 3 X g X,f = ✏ e Q f . cos 2 ✓ W ( m 2 f m 2 Z � m 2 Z � m 2 X ) X For small mass it mili-couples to electric current (hence hidden photon) Another consequence of mixing: hidden photon mixes with Z boson m 2 ˆ ˆ + O ( ✏ 2 ) Z Z µ = cos ↵ Z µ +sin ↵ X µ , X µ = � sin ↵ Z µ +cos ↵ X µ , ↵ ⇡ ✏ tan ✓ W m 2 Z � m 2 X Therefore it couples to Higgs m 2 c hZX = 2 ✏ tan ✓ W m 2 Z X + O ( ✏ 2 ) . L hZX = c hZX v hZ µ X µ , m 2 Z � m 2 X
Hidden photon in the golden channel Higgs can decay as h � Z X � 4l!
Hidden photon - constraints from 4l Event count in the h � 4l channel ∆Γ h → 4 µ ∆Γ h → 2 e 2 µ ∆Γ h → 4 e 10 - 2 < 0 . 90 , < 0 . 83 , < 1 . 27 , Γ SM Γ SM Γ SM h → 4 µ h → 2 e 2 µ h → 4 e Br H h Æ ZX L 10 - 3 ∆Γ h → 4 ` < 0 . 52 . 10 - 4 Γ SM h → 4 ` 10 15 20 25 30 35 m X @ GeV D
Hidden photon in the golden channel Kinetic mixing with hidden photon affects Z mass and Z couplings to matter Z + ✏ 2 tan 2 ✓ W ˆ m 4 m 2 m 2 + O ( ✏ 3 ) , Z Z = ˆ m 2 m 2 Z � ˆ X 1 � ✏ 2 tan 2 ✓ W m 4 tan 2 ✓ W m 2 ✓ ◆ � ✏ 2 q Z Z g 2 L + g 2 g Z,f = ˆ g Z,f Y f , Y ( m 2 Z � m 2 m 2 Z � m 2 X ) 2 X q Fitting to LEP-1 and W mass data s 1 � m 2 X | ✏ | . 0 . 024 at 95% C . L ., m 2 Z
Hidden photon in the golden channel Electroweak Precision Observables imply s 1 � m 2 X | ✏ | . 0 . 024 at 95% C . L ., m 2 Z for 10 GeV < mX < mZ, and stronger bounds below from B-factories Follows the bound on branching fraction h � Z X 10 - 2 Br H h Æ ZX L 10 - 3 10 - 4 10 15 20 25 30 35 m X @ GeV D
Hidden photon - constraints from 4l Parameter Space 0.10 4l 0.08 r a B 0.06 a B Ε 0.04 EWPO 0.02 10 20 30 40 50 60 70 m X @ GeV D
Hidden photon - constraints from 4l Larger Parameter Space 10 - 1 CMS 10 - 3 EWPM 10 - 2 10 - 4 WASA a m , 5 s BaBar KLOE 10 - 5 Br H h Æ ZZ D L = 10 - 6 a m , ± 2 s favored 10 - 3 e APEX ê MAMI a e E774 E141 10 - 4 PROMPT NON - PROMPT Orsay U70 10 - 5 10 - 3 10 - 2 10 - 1 1 10 1 Curtin et al, 1312.4992 m Z D @ GeV D
Hidden photon in the golden channel Simple modification of hidden photon model ✓ | H | 2 | H | 2 ◆ � 1 ✏ 2 ✏ 3 B µ ν ˆ B µ ν ˆ ˜ ∆ L = X µ ν + X µ ν , v 2 v 2 cos ✓ W 2 cos ✓ W ε 2 =0.02 ε 3 =0.02 10 - 2 Larger branching Br H h Æ ZX L fractions for 10 - 3 h � ZX now allowed 10 - 4 10 15 20 25 30 35 m X @ GeV D
Hidden photon in the golden channel ª L H fb - 1 L û 14 TeV H pp Æ h Æ 4l L 500 1500 2500 ª L H fb - 1 L û 14 TeV H pp Æ h Æ 4l L 10 50 150 250 5 35 Hidden Photon » e » = 0.02 8 Hidden Photon 20 » e » = 0.02 4 25 30 35 40 25 6 30 60 H e = 0.018 L 3 s 3 s s 20 40 4 15 95 % 2 3 s 60 H e = 0.018 L 15 95 % 2 1 10 H M 2 > 5 GeV L 10 H M 2 > 5 GeV L 50 150 250 350 450 550 500 1500 2500 3500 4500 5500 N N → × m X ✏ ✏ 2 ✏ 3 R 10 0.02 0 0 1.004 15 0.02 0 0 1.006 20 0.02 0 0 1.019 25 0.02 0 0 1.031 30 0.02 0 0 1.039 30 0.02 0.01 0 1.33 30 0.02 0 0.015 1.20 35 0.02 0 0 1.019 40 0.02 0 0 1.019 50 0.02 0 0 1.016 60 0.018 0 0 1.014 For mX close to 25-35 GeV vanilla model
Hidden photon in the golden channel ª L H fb - 1 L û 14 TeV H pp Æ h Æ 4l L 500 1500 2500 ª L H fb - 1 L û 14 TeV H pp Æ h Æ 4l L 10 50 150 250 5 35 Hidden Photon » e » = 0.02 8 Hidden Photon 20 » e » = 0.02 4 25 30 35 40 25 6 30 60 H e = 0.018 L 3 s 3 s s 20 40 4 15 95 % 2 3 s 60 H e = 0.018 L 15 95 % 2 1 10 H M 2 > 5 GeV L 10 H M 2 > 5 GeV L 50 150 250 350 450 550 500 1500 2500 3500 4500 5500 N N For mX close to 15-65 GeV vanilla model probed in LHC run-2 Exclusion reach down to 10 GeV in high- luminosity LHC For mX close to 25-35 GeV vanilla model
Hidden photon in the golden channel Practically all discrimination power from shape analysis ε =0.02 Shape vs Rate m X =30 GeV 3.0 2.5 2.0 Σ 1.5 1.0 0.5 0.0 50 100 150 200 250 N
Hidden photon in the golden channel ª L H fb - 1 L û 14 TeV H pp Æ h Æ 4l L 15 25 35 6 Hidden Photon H m X , e , e 2 , e 3 L 5 ZX Only --- 4 H 30, 0.02, - 0.01, 0 L H 30, 0.02, 0, 0.015 L s 3 s 3 95 % 2 H 30, 0.02, 0, 0 L 1 25 50 75 N Modified hidden photon model already being probed ✓ | H | 2 | H | 2 ◆ � 1 ✏ 2 ✏ 3 B µ ν ˆ B µ ν ˆ ˜ ∆ L = X µ ν + X µ ν , v 2 v 2 cos ✓ W 2 cos ✓ W
Hidden photon in the golden channel Still better discrimination power from shape than rate 10 Shape+Rate Shape 8 6 Σ → × 4 Rate m X ✏ ✏ 2 ✏ 3 R 2 10 0.02 0 0 1.004 15 0.02 0 0 1.006 0 20 0.02 0 0 1.019 50 100 150 200 250 300 25 0.02 0 0 1.031 N 30 0.02 0 0 1.039 30 0.02 0.01 0 1.33 30 0.02 0 0.015 1.20 35 0.02 0 0 1.019 40 0.02 0 0 1.019 50 0.02 0 0 1.016 60 0.018 0 0 1.014
Summary part 1 Exotic Higgs decays may be the portal to new physics Large exotic decay rates readily possible if there exists a light BSM degree of freedom coupled to Higgs Exotic decays could show up in standard Higgs analyses, e.g. in the golden channel
New CP violating observables in Higgs decays
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