No abstract

We study the prospects of observing the non-resonant di-Higgs pair production in the Standard Model (SM) at the high luminosity run of the 14 TeV LHC (HL-LHC), upon combining multiple final states chosen on the basis of their yield and cleanliness. In particular, we consider the bbγγ, bbτ + τ − , bbW W * , W W * γγ and 4W channels mostly focusing on final states with photons and/or leptons and study 11 final states. We employ multivariate analyses to optimise the discrimination between signal and backgrounds and find it performing better than simple cut-based analyses. The various differential distributions for the Higgs pair production have non-trivial dependencies on the Higgs self-coupling (λ hhh ). We thus explore the implications of varying λ hhh for the most sensitive search channel for the double Higgs production, viz., bbγγ. The number of signal events originating from SM di-Higgs production in each final state is small and for this reason measurement of differential distributions may not be possible. In order to extract the Higgs quartic coupling, we have to rely on the total number of events in each final state and these channels can be contaminated by various new physics scenarios. Furthermore, we consider various physics beyond the standard model scenarios to quantify the effects of contamination while trying to measure the SM di-Higgs signals in detail. In particular, we study generic resonant heavy Higgs decays to a pair of SM-like Higgs bosons or to a pair of top quarks, heavy pseudoscalar decaying to an SM-like Higgs and a Z-boson, charged Higgs production in association with a top and a bottom quark and also various well-motivated supersymmetric channels. We set limits on the cross-sections for the aforementioned new physics scenarios, above which these can be seen as excesses over the SM background and affect the measurement of Higgs quartic coupling. We also discuss the correlations among various channels which can be useful to identify the new physics model. 2.5.3 The 4 final state 35 2.6 Summarising the non-resonant search results 36 3 Ramifications of varying the Higgs self-coupling 37 4 Contaminations to non-resonant di-Higgs processes 40 4.1 The hh(+X) channels 41 4.2 The h + X channels 46 4.3 Null Higgs channels 49 A Appendix A 68 B Appendix B 69

We show that in studies of light quark-and gluon-initiated jet discrimination, it is important to include the information on softer reconstructed jets (associated jets) around a primary hard jet. This is particularly relevant while adopting a small radius parameter for reconstructing hadronic jets. The probability of having an associated jet as a function of the primary jet transverse momentum (p T ) and radius, the minimum associated jet p T and the association radius is computed up to next-to-double logarithmic accuracy (NDLA), and the predictions are compared with results from Herwig++, Pythia6 and Pythia8 Monte Carlos (MC). We demonstrate the improvement in quark-gluon discrimination on using the associated jet rate variable with the help of a multivariate analysis. The associated jet rates are found to be only mildly sensitive to the choice of parton shower and hadronization algorithms, as well as to the effects of initial state radiation and underlying event. In addition, the number of k t subjets of an anti-k t jet is found to be an observable that leads to a rather uniform prediction across different MC's, broadly being in agreement with predictions in NDLA, as compared to the often used number of charged tracks observable.

We discuss the indirect detection of the wino dark matter utilizing gammaray observations of dwarf spheroidal galaxies (dSphs). After carefully reviewing current limits with particular attention to astrophysical uncertainties, we show prospects of the wino mass limit in future gamma-ray observation by the Fermi-LAT and the GAMMA-400 telescopes. We find that the improvement of the so-called J-factor of both the classical and the ultra-faint dSphs will play a crucial role to cover whole mass range of the wino dark matter. For example, with δ(log 10 J) = 0.1 for both the classical and the ultra-faint dSphs, whole wino dark matter mass range can be covered by 15 years and 10 years data at the Fermi-LAT and GAMMA-400 telescopes, respectively.Since the discovery of a new boson at the Large Hadron Collider (LHC) [1], which seems strongly to be the Higgs boson of the standard model (SM), people have started examining candidates of new physics beyond the SM more closely. One of the most striking hints from the discovery is that its mass is observed at about 126 GeV, which indicates that the new physics behind the Higgs mechanism is presumably described by a weakly-interacting theory. Among several weakly interacting extensions of the SM, supersymmetry (SUSY) has been considered so far as the most promising candidate. When SUSY particles exist within a TeV range as expected in the pre-LHC era, however, the Higgs boson mass of 126 GeV is difficult to be achieved in the minimal supersymmetric extension of the SM. Rather, larger SUSY breaking effects are mandatory to push up the Higgs boson mass, which in turn requires the typical mass scale of sparticles to be much higher than 1 TeV [2]. Such high-mass sparticles are actually not only compatible with null-observations of new physics signals at the LHC experiment, but also ameliorate the problem of too large SUSY contributions to flavor-changing neutral current (FCNC) processes.An apparent downside of high-mass sparticles is the loss of a good candidate for dark matter. When the dark matter is one of the sparticles with the mass much larger than 1 TeV, its predicted mass density is too high to be consistent with the observation [3]. This problem is, however, naturally resolved in a class of models of supergravity mediation if the SUSY breaking sector does not include any singlet fields [4,5]. In the models, all scalar particles acquire their masses of the order of the gravitino mass via tree level interactions, while gaugino masses are dominated by one-loop anomaly mediated contributions [4,6]. #1 On top of these features, the models predict the lightest supersymmetric particle (LSP) to be the almost pure neutral wino in most parameter space. The neutral wino is known to be a good candidate for a weakly interacting massive particle (WIMP) dark matter when its mass is of O(1) TeV [12]- [14]. Therefore, when the gravitino mass is in the range of tens to hundreds TeV range, we can realize a hierarchical spectrum appropriate to explain the observed Higgs boson mass while having a...

The measurement of forward-backward asymmetry in the top and anti-top quark (tt) production has been recently reconfirmed by the CDF Collaboration and shows a more than 3σ deviation from the Standard Model(SM) prediction in the large tt invariant mass region. Models with new W ′ or Z ′ bosons have been invoked to explain this deviation. In the context of these models we perform a χ 2 analysis with all the available experimental numbers in different ∆Y and M tt bins. We show that for the Z ′ model the region of parameter space which explain the Tevatron asymmetry can be probed in the same sign top production channel by Tevatron itself. Moreover, we consider a recently proposed observable, the one sided forward-backward asymmetry (A OF B ) at the LHC and conclude that both the W ′ and Z ′ models can lead to sizable A OF B even at the LHC running at a center of mass energy of 7 TeV for the model parameters consistent with the Tevatron measurements. * biplob@theory.tifr.res.in † sudhansu@theory.tifr.res.in ‡ diptimoyghosh@theory.tifr.res.in

Run-I results from the CMS collaboration show an excess of events in the decay h → µτ e with a local significances of 2.4σ. This could be the first hint of flavour violation in the Higgs sector. We summarise the bounds on the flavour violating Yukawa couplings from direct searches, low energy measurements and projected future experiments. We discuss the sensitivity of upcoming HL-LHC runs and future lepton colliders in measuring leptonflavour violating couplings using an effective field theory framework. For the HL-LHC we find limits on BR(h → µτ ) and BR(h → eτ ) O(0.5)% and on BR(h → eµ) O(0.02)%. For an ILC with center-of-mass energy of 1 TeV we expect BR(h → eτ ) and BR(h → µτ ) to be measurable down to O(0.2)%.

In the minimal Universal Extra Dimension model, single production of n = 2 gauge bosons provides a unique discriminating feature from supersymmetry. We discuss how the proposed International Linear Collider can act as a n = 2 factory, much in the same vein as LEP. We also touch upon the potential of the γγ mode of the collider to study the production and the decay of an intermediate mass Higgs boson and its KK excitations.

Here, we give a broad overview of the more natural spectra allowed by the LHC when U DD R-parity violation is allowed. Because R-parity violation removes the missing energy signals in colliders, the experimental constraints on the gluino, stops, sbottoms and higgsinos are relatively mild. We also show that U DD R-parity violation and lepton number conservation can be made consistent with grand unification. This feat is achieved through the product unification, SU (5) × U (3). In this model, mixing of the SM quarks with additional quark like particles charged under the U (3) generate a U DD R-parity violating operator. Furthermore, these models are also capable of generating a "natural" spectra. The emergence of these more natural low-scale spectra relies heavily on the fact that the gaugino masses are non-universal, a natural consequence of product unification.