No abstract

The LHC sensitivity to an anomalous Higgs coupling to the top quark in the Higgs-top associated production is analyzed. Thanks to the strong destructive interference in the t-channel for standard model couplings, this process can be very sensitive to both the magnitude and the sign of a nonstandard top-Higgs coupling. We analyze cross sections and the main irreducible backgrounds for the H → γγ decay channel. Sensitivities to an anomalous sign for the top Yukawa coupling are found to be large. In particular, at s√=14TeV , assuming a universal rescaling in the Yukawa sector, a parton-level analysis with realistic selection cuts gives a signal-to-background ratio S/B ~ 5, for −1.5≲Yt/YSMt≲0 . A number of events S ≃ 10 (with corresponding significances ~ 3 σ) are expected for 60 fb−1, to be compared with the standard-model expectation S ~ 0.3

Abstract:The recent results from the LHCb in the context of (B + → K + ll) decay and the CMS analysis in the context of right handed W -boson (W R ) search show a 2.6σ and a 2.8σ deviations from the Standard Model expectations respectively. In this work, we address these two seemingly uncorrelated results in the context of R-parity violating supersymmetry. We found that a particular combination of LQD c -type operators which successfully explain the LHCb result, can also accommodate the CMS excess in the eejj channel of the W R search.

Abstract:We study the production of a Higgs boson recoiling from a massless invisible system in e + e − collisions. This is a quite distinctive signature that can arise when the Higgs boson is produced in association with a massless dark photon, which can happen in BSM scenarios foreseeing an extra unbroken U(1) gauge group. Dark photons can indeed acquire effective couplings to the Higgs boson as occurs in models recently proposed to generate exponentially-spread Yukawa couplings. We analyze the signal and corresponding backgrounds for H → bb, and estimate ILC and FCC-ee sensitivities in a model-independent way.

Dark photons γ¯ mediating long-range forces in a dark sector are predicted by various new physics scenarios, and are being intensively searched for in experiments. We extend a previous study of a new discovery process for dark photons proceedings via Higgs-boson production at the LHC. Thanks to the non-decoupling properties of the Higgs boson, BR(H→γγ¯) values up to a few percent are possible for a massless dark photon, even for heavy dark-sector scenarios. The corresponding signature consists (for a Higgs boson at rest) of a striking monochromatic photon with energy Eγ=mH/2, and similar amount of missing energy. We perform a model independent analysis at the LHC of both the gluon-fusion and VBF Higgs production mechanisms at 14 TeV, including parton-shower effects, and updating our previous parton-level analysis at 8 TeV in the gluon-fusion channel by a more realistic background modeling. We find that a 5σ sensitivity can be reached in the gluon-fusion channel for BR(H→γγ¯)≃0.1% with an integrated luminosity of L≃300fb−1. The corresponding VBF reach is instead restricted to 1%. Such decay rates can be naturally obtained in dark-photon scenarios arising from unbroken U(1)F models explaining the origin and hierarchy of the Yukawa couplings, strongly motivating the search for this exotic Higgs decay at the LHC

We consider a supergravity (SUGRA) scenario, with universal scalar and gaugino masses at high scale, with a right-chiral neutrino superfield included in the spectrum. Such a scenario can have a lightest supersymmetric particle (LSP) dominated by the right sneutrino and a stau as the next-to lightest supersymmetric particle (NLSP). Since decays of all particles into the LSP are suppressed by the neutrino Yukawa coupling, the signal of supersymmetry consists in charged tracks of stable particles in the muon chamber. We demonstrate how a neutralino decaying into a tau and the stau-NLSP can be fully reconstructed over substantial areas in the SUGRA parameter space. We also suggest event selection criteria for eliminating backgrounds, including combinatorial ones, and use a new method for the extraction of the mass of the stau-NLSP, using its three-momentum as obtained from the curvature of the charged track.Comment: Version to appear in Phys. Rev.

Recent CMS searches for dileptoquark production report local excesses of 2Ao in an eejj channel and 2.6a in an eprjj channel. Here, we simultaneously explain both excesses with resonant slepton production in 72-parity violating supersymmetry. We consider resonant slepton production, which decays to a lepton and a chargino/neutralino, followed by three-body decays of the neutralino/chargino via an 72-parity violating coupling. There are regions of parameter space which are also compatible at the 95% confidence level with a 2.8a eejj excess in a recent CMS WR search, while being compatible with other direct search constraints. Phase II of the GERDA neutrinoless double beta decay (Duft/S) experiment will probe a sizable portion of the good-fit region. The recent CM S search for dileptoquark production found, with a certain set o f cuts, a 2.4cr local excess in the eejj channel and a 2.6 c local excess in an ePT j j channel1 in com parison to Standard M odel (SM ) expect ations. The CM S searches use pp collision data at the Large H adron C ollider (LHC) and a center o f mass energy o f 8 TeV and 19.6 f t r 1 o f integrated luminosity. Requiring a certain set o f cuts (called "MLq = 650 G eV " cuts), CMS reported 36 events on a background2 o f 20.5 ± 3.5 in the eejj channel, and 18 events on a background o f 7.5 ± 1 .6 in the evjj channel [1]. Taken sim ultaneously and ignoring correlations betw een the systematics, these excesses am ount to a 3.5cr effect. In addition, a WR search (with different cuts to the dileptoquark search) reported a 2.80-excess in the eejj channel at 1.8 TeV < Meejj < 2.2 TeV [2]. These excesses are not significant enough to claim a discovery, or even evidence. They are sim ilar enough to attem pt a unified explanation of all three, and a timely explanation before the next LHC run (ran II) in terms of new physics such that further tests can be applied and analysis strategies can be set for run II.There have been a few attempts to explain the CMS excesses with different models. Coloron-assisted leptoquarks were proposed in Ref. [3]. The WR excess was interpreted in grand unified theory m odels in Refs. [4,5], In Ref. [6], pair production o f vectorlike leptons was proposed via W '/Z ' vector bosons. Reference [7] perform ed a detailed analysis (including a general flavor structure) of W'/Z' interpretations o f the WR search data. In Ref. [8], it was supposed that leptoquarks consistent with the 1 CMS refers to this channel as evjj, and we shall from here use the same nomenclature. 2We have added systematic and statistical errors in quadrature. dileptoquark excess decay into dark m atter particles with a significant branching ratio. Reference [9] explains the dileptoquark excesses with di-sbottom production, fol lowed by 72-parity violating (RPV) decay. In a previous article [10], w e proposed that resonant slepton production was responsible for the WR search excess in RPV supersymmetry. One o f us showed that this explanation is also consistent with recent deviations from SM prediction m easur...

The strength of forward-backward (FB) multiplicity correlations is measured by the ALICE detector in proton-proton (pp) collisions at √ s = 0.9, 2.76 and 7 TeV. The measurement is performed in the central pseudorapidity region (|η| < 0.8) for the transverse momentum p T > 0.3 GeV/c. Two separate pseudorapidity windows of width (δη) ranging from 0.2 to 0.8 are chosen symmetrically around η = 0. The multiplicity correlation strength (b corr) is studied as a function of the pseudorapidity gap (η gap) between the two windows as well as the width of these windows. The correlation strength is found to decrease with increasing η gap and shows a non-linear increase with δη. A sizable increase of the correlation strength with the collision energy, which cannot be explained exclusively by the increase of the mean multiplicity inside the windows, is observed. The correlation coefficient is also measured for multiplicities in different configurations of two azimuthal sectors selected within the symmetric FB η-windows. Two different contributions, the short-range (SR) and the long-range (LR), are observed. The energy dependence of b corr is found to be weak for the SR component while it is strong for the LR component. Moreover, the correlation coefficient is studied for particles belonging to various transverse momentum intervals chosen to have the same mean multiplicity. Both SR and LR contributions to b corr are found to increase with p T in this case. Results are compared to PYTHIA and PHOJET event generators and to a string-based phenomenological model. The observed dependencies of b corr add new constraints on phenomenological models.