Theory of Higgs to tau signals at the

Theory of Higgs to tau signals at the LHC Hiroshi YOKOYA (Toyama U) ~200 km The 12 th International Workshop on Tau Lepton Physics Nagoya, Japan, 17 -21 September, TAU 2012 H. Yokoya (Toyama U) 2012

Outline of this talk: 1. Introduction 2. Tau-lepton at colliders 3. Tau-lepton and Higgs physics 4. Summary TAU 2012 H. Yokoya (Toyama U) 2

1. Introduction In the era of LHC and Higgs physics, tau-lepton has a great potential. Thanks to the long history of theoretical and experimental studies on tau lepton, collected in a series of this workshop. • Yukawa coupling is proportional to its mass, yμ/yτ~mμ/mτ (cf. gauge coupling universality) • Techniques prepared for theory (Decay ME, simulation tools, reconstruction) and experiment (tau-jet tagging, triggering, , , ). • (Tentative) interest in the deficit of h > tau. TAU 2012 H. Yokoya (Toyama U) 3

2. Tau-lepton at colliders Decay, Tau-jet tagging, Collinear approximation, Polarizations, , , TAU 2012 H. Yokoya (Toyama U) 4

Tau-lepton decay Tau decay includes always tau-neutrino. • Leptonic decay ~ 35% • Hadronic decay ~ 65% 1 -prong decay: 3 -prong decay: TAU 2012 H. Yokoya (Toyama U) 5

Tau-jet tagging • Hadronic tau decay contains mostly 1 or 3 charged particles (pions). • Because of its light mass compared to the collider energy scale, produced tau is highly boosted and its decay products are collimated. Tau-jet tagging: 1 or 3 charged hadrons in a collimation cone (Rem) accompanied by an isolation cone around that (Rtracks). (E. g. , Rem=0. 15 and Rtracks=0. 5) Roughly ~ 50 -70% tagging efficiency with mis-ID probability a few % for light jet. τ→πν decay can be extracted by requiring single π± with low Ecal energy deposit (π0). TAU 2012 H. Yokoya (Toyama U) 6

Collinear approximation At the colliders, tau is highly boosted: • Thus, it is good approximation to take the direction of the tau momentum to that of its decay product. (Direction (2 dim. ) of the 3 -momentum is fixed, but only the energy fraction is unknown. ) • It makes possible a momentum reconstruction of some event with tau leptons. e. g. h > tau in VBF Rainwater, Zeppenfeld, Hagiwara (’ 98) TAU 2012 H. Yokoya (Toyama U) 7

Tau-lepton polarization Bullock, Hagiwara, Martin; TAUOLA Polarization dependence of the tau decay distribution is well-known. Especially, pionic decay distribution has large analysis power of the tau’s polarization. Tau polarization and its correlation is useful to distinguish spin or models for parent particles. TAU 2012 H. Yokoya (Toyama U) 8

Tau-lepton polarization Polarization dependence survives in the tagged tau-jets. • Single-pion-like jet : spin analyzing power is large • 1+3 prong jet : weak, but large tagging efficiency Sim. TAUOLA + Pythia Red: left-handed tau Blue: right-handed tau Sugiyama, Tsumura, HY (’ 12) → K. Tsumura TAU 2012 H. Yokoya (Toyama U) 9

3. Tau-lepton and Higgs physics SM Higgs boson search, Extended Higgs boson search (multi-tau-lepton signatures, 4 -tau event reconstruction, , , ) TAU 2012 H. Yokoya (Toyama U) 10

SM Higgs boson Search → J. Benitez, M. Morinaga, Y. Sakurai • Useful channel because it can be measured in various production processes. • Higgs mass can be reconstructed by using the collinear approximation. • CMS Search Results (2012. 07) TAU 2012 H. Yokoya (Toyama U) 11

Extended Higgs bosons Search Two Higgs Doublet Model : Type-II (SUSY-like) and Type-X models, Yukawa interaction to tau is enhanced. → Large branching ratio into tau(nu). SUSY Higgs Search with τ • Br(h+>τν)~1 for m. H+<mt → C. Ferro, • Search for gg > H(A) > ττ, gg > H(A)bb > ττbb → R. Reece, enhanced by tan 2β T. Mitani TAU 2012 H. Yokoya (Toyama U) 12

Extended Higgs bosons Search Aoki, Kanemura, Tsumura, Yagyu (‘ 09) Type-X THDM: Less bound from flavor data. Only LEP bound gives m > 100 Ge. V. ~ • Low mass search can be performed at the LHC Gluon fusion is suppressed by tanβ, Pair (associated) production gives leading → Multi-tau-lepton signatures (4τ, 3τ) Kanemura, Tsumura, HY (‘ 11) TAU 2012 H. Yokoya (Toyama U) 13

Multi-tau-lepton signatures L = e μ • Various final-states depending on the tau’s decay pattern. H A τ+ τ- 4τh τh τh 3τh 1 L τh τh τh L 2τh 2 L τh τh L L 1τh 3 L τh L L L 4 L L L TAU 2012 H. Yokoya (Toyama U) 14

Multi-tau-lepton signatures • Due to the multiple high-p. T tau-jet requirement, a large s/b ratio and significance is expected (/S=14 Te. V, L=100 fb-1). Selection cuts for 4 tau-jet events τh τh 3 tau-jets + 1 lepton, 2 tau-jets + 2 leptons are also useful • Alternatively, use μμ decay: small BR but clean signal is expected. H Sharp dimuon peaks at m. H and m. A. TAU 2012 H. Yokoya (Toyama U) A τ+ τμ+ μ- 15

Kinematic reconstruction in 4 -tau events ILC: easily solved. 4 missing particles (directions are known) v. s. 4 energy-momentum conservation. z 1 z 2 z 3 z 4 TAU 2012 H. Yokoya (Toyama U) Kanemura, Tsumura, HY 16

Kinematic reconstruction in 4 -tau events LHC: impossible since only transverse momentum conservation can be available. But, if the two resonance masses are same, assuming the mass of di-tau resonances, it could be solved. Hagiwara, HY in progress (e. g. , m. H=m. A in 2 HDM, H++H-- in Triplet Higgs Model. ) z 1 Min • How to determine the mass ? Parameter scan by the trial mass (Min), Min z 2 z 3 z 4 then look at the number-of-solution distribution. TAU 2012 H. Yokoya (Toyama U) 17

Kinematic reconstruction in 4 -tau events (Quartic) Equations to solve: TAU 2012 H. Yokoya (Toyama U) ina im • Need to calculate recoil transverse momenta from ISR-jet momenta. (Black: Sim. w/o ISR, Red: Sim. w ISR) pre l • Its derivative function has a peak at the true mass. ry • Number of no-solution events as a function of the trial mass. 18

4. Summary In the era of LHC and Higgs physics, tau lepton has a great potential. • Tau has large coupling to Higgs boson. It can be more enhanced to the extended scalars. (Type-II or X THDM, Triplet Higgs Model for neutrino mass, , , ) • Tau tagging efficiency is good at the LHC. • Collinear approximation (Tau’s momentum direction is known). • Polarization can be used to probe interactions or parent particle’s spin. • Simulation tools are well prepared. • New challenges for more complicated signatures. (Multi-tau-lepton signatures, Momentum reconstruction, , , ) TAU 2012 H. Yokoya (Toyama U) 19

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Tagging efficiency ATLAS-CONF-2011 -077 Tau tagging efficiency and mis-ID probability finding efficiency ~ 0. 8 with mis-ID prob. ~ 0. 1 (for the 1/3 track(s) jets) TAU 2012 H. Yokoya (Toyama U) 21

SM with 4 th generation? 4 th generation model is excluded by the Higgs measurements No more “chiral” heavy quark, “vector-like” is still possible. t’/b’ loop effect is non-decoupling • gg>h cross-section enhanced by a factor 9. • Br(h>γγ) suppressed due to the destructive interference with W-loop. • (h>bb mode is measured in VH channel. ) • h>ττ gives the most stringent constraint. TAU 2012 H. Yokoya (Toyama U) 22

Multi-tau-lepton signatures τh TAU 2012 H. Yokoya (Toyama U) τh τh τh 23

Multi-tau-lepton signatures τh • Higgs masses may be obtained by finding endpoints of τh τh τh distributions. • Pairing of tau-jets from the four can be chosen for the pair which has max. transverse momentum of tau-jet-pair, or which has smallest distance. TAU 2012 H. Yokoya (Toyama U) 24

Triplet Higgs bosons Search Higgs Triplet Model (Y=1): A model to generate Majorana neutrino mass by triplet VEV (vΔ < a few Ge. V by ρ-parameter). We know neutrino mixing is large → Off-diagonal vertex is sizable. • Search for the same-sign dilepton resonance at the LHC TAU 2012 H. Yokoya (Toyama U) 25

Triplet Higgs bosons Search CMS-HIG-12 -005 TAU 2012 H. Yokoya (Toyama U) 26