Searching for Heavy Charged Higgs Boson with Jet Substructure at the LHC
Shuo Yang, Qi-Shu Yan
备注：
27 pages, 10 figures, 7 tables; v2: some typos corrected and references added; v3: discussion added, Fig.10 and Table7 updated, version published in JHEP
We study the heavy charged Higgs boson (from 800 GeV to 1500 GeV in this study) in production associated with a top quark at the LHC with the collision energy $\sqrt{s}=14$ TeV. Such a heavy charged Higgs boson can dominantly decay into a top quark and a bottom quark due to its large Yukawa couplings, like in MSSM. To suppress background events and to confirm the signal, we reconstruct the mass bumps of the heavy charged Higgs boson and the associated top quark. For this purpose, we propose a hybrid-R reconstruction method which utilizes the top tagging technique, a jet substructure technique developed for highly boosted massive particles. By using the full hadronic mode of $p p \to H^{\pm} t \to t tb$ as a test field, we find that this method can greatly reduce the combinatorics in the full reconstruction and can successfully reduce background events down to a controlled level. The sensitivity of LHC to the heavy charged Higgs boson with two $b$ taggings is studied and a $9.5σ$ significance can be achieved when $m_{H^\pm} =1 \textrm{TeV}$.
We present indications of possible substructures from weak interactions, by inspecting LEP and LHC date and inferring threshold effects due to the production of pairs of composite heavy gauge bosons W+-, Z and their hypothetical partners with different spin. Thus, we find possible evidence of scalar or pseudoscalar partners of the W+- and the Z, viz. at 53 and 57 GeV, respectively. Additionally, data may indicate excited states of the Z at 210 and 240 GeV.
It is widely believed that searching for a light Higgs boson (with a mass around 120 GeV) in the WH and ZH channels, where H decays into $b\bar{b}$, will be very challenging at the LHC. These proceedings describe how this channel can be recovered as a promising search channel at high $p_t$ by using a subjet analysis procedure.
These proceedings discuss a possible new search strategy for a light Higgs boson at the LHC, in high-pt WH and ZH production where the Higgs boson decays to a single collimated b-bbar jet. Material is included that is complementary to what was shown in the original article, arXiv:0802.2470.
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Weak boson fusion is a copious source of intermediate mass Higgs bosons at the LHC, with a rate sigma*B(H -> gamma gamma) of up to 9 fb. The additional very energetic forward jets in these events provide for a unique signature. A parton level analysis of the dominant backgrounds demonstrates that this channel allows the observation of H -> gamma gamma in a low background environment, with modest luminosity.
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Heavy Neutral Leptons are naturally present in many well-motivated extensions of the Standard Model. If their mass is of few dozens of GeVs, they can be long-lived and lead to events with displaced vertices, giving rise to promising signatures due to the low background. We revisit the opportunities offered by the LHC to discover these long-lived states via searches with displaced vertices. We study in particular the implication on the parameter space sensitivity when all mixings to active flavors are taken into account.
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Despite rather long-term theoretical and experimental studies, the hypothesis of the non-zero intrinsic (or valence-like) heavy quark component of the proton distribution functions has not yet been confirmed or rejected. The LHC with $pp$-collisions at $\sqrt{s}=$ 7--14 TeV will obviously supply extra unique information concerning the above-mentioned component of the proton. To use the LHC potential, first of all, one should select the parton-level (sub)processes (and final-state signatures) that are most sensitive to the intrinsic heavy quark contributions. To this end inclusive production of…
It is widely considered that, for Higgs boson searches at the Large Hadron Collider, WH and ZH production where the Higgs boson decays to b anti-b are poor search channels due to large backgrounds. We show that at high transverse momenta, employing state-of-the-art jet reconstruction and decomposition techniques, these processes can be recovered as promising search channels for the standard model Higgs boson around 120 GeV in mass.
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We reexamine the prospects for searching for a neutral Higgs boson in the intermediate-mass range and physics beyond the standard model, using the proton- and ion-beam facilities of the LHC to study coherent two-photon processes. Considering realistic design luminosities for the different ion beams, we find that beams of light-to-medium size ions like calcium will give the highest production rates. With a suitable trigger and assuming a b-quark identification efficiency of $30\%$ and a $b{\bar b}$ mass resolution of 10 GeV one could expect to see a Higgs signal in the $b{\bar b}$ channel with …
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We consider a dark sector containing a pair of almost degenerate states coupled to the Standard Model through a dark photon mediator. This set-up constitutes a simple realization of the inelastic dark matter scenario. The heaviest dark state is long-lived, in the limit of a small kinetic mixing among the dark photon and the Standard Model hypercharge gauge boson, and/or of a small mass splitting among the dark states. We study the prospects for detection of this scenario at proposed LHC experiments dedicated to search for long-lived particles, namely FASER, MATHUSLA, CODEX-b, AL3X, MAPP, ANUBI…
Over the last years, new physics in terms of a novel weakly-interacting massive particle (WIMP) has come more and more under pressure from experimental null results. While the remaining WIMP parameter space will be probed by next generation dark matter experiments, models of light new physics have become increasingly popular over the last decade. In an effort to explore the parameter space of such light physics, a myriad of custom designed high-precision/low-energy experiments has been proposed. In this note, however, I argue that existing LHC multipurpose experiments like ATALS and CMS have a…
Fermion masses may arise via mixing of elementary fermions with composite fermions of a strong sector in scenarios of strongly-coupled electroweak symmetry breaking. The strong sector may contain leptoquark states with masses as light as several hundred GeV. In the present study we focus on the scalar modes of such leptoquarks since their bosonic couplings are determined completely and hence their production cross sections only depend on their masses. We study all the possible gauge-invariant non-derivative and single-derivative couplings of the scalar leptoquarks to the quarks and leptons, wh…
There seem to be recently an evidence for $C = -1$ odderon exchange in proton-proton elastic scattering at high energies. Here we discuss three different central-exclusive-production processes $pp \to pp (ϕ\to K^{+}K^{-})$, $pp \to pp (ϕ\to μ^{+}μ^{-})$, and $pp \to pp ϕϕ\to pp K^{+}K^{-}K^{+}K^{-}$, as a possible source of information for soft odderon exchange. The theoretical results are calculated within the tensor-pomeron and vector-odderon model for soft reactions. We include absorptive corrections at the amplitude level. To describe the low-energy data measured in the past by the WA102 c…
The CP-odd Higgs boson $A^0$ of the Minimal Supersymmetric Standard Model (MSSM) and Two Higgs Doublet Model (2HDM) will usually decay into the heaviest possible fermion -- antifermion pair available. The $A^0 \to VV$ decay where, $V =γ, Z, W^\pm$, and gluons are of particular interest as they are not allowed at tree level and hence they may offer information about the underlying new physics that enters at one loop level. In this paper all branching ratios of the CP-odd Higgs boson $A^0$ both in the MSSM and 2HDM are presented for this channel including all relevant Standard Model (SM) and MSS…
Collider signals of dark photons are an exciting probe for new gauge forces and are characterized by events with boosted lepton jets. Existing techniques are efficient in searching for muonic lepton jets but due to substantial backgrounds have difficulty constraining lepton jets containing only electrons. This is unfortunate since upcoming intensity frontier experiments are sensitive to dark photon masses which only allow electron decays. Analyzing a recently proposed model of kinetic mixing, with new scalar particles decaying into dark photons, we find that existing techniques for electron je…
We discuss the double-parton scattering (DPS) effects in four-jet production at the LHC. A special attention is given to the optimization of kinematical conditions in order to enhance the relative contribution of DPS in four-jet sample. The calculations of single-parton and double-parton scattering components are done in the high-energy (or $k_{T}$)-factorization approach. Here we follow our recent developments of relevant methods and tools that are implemented in the AVHLIB Monte Carlo library. Several differential distributions are calculated and carefully discussed in the context of recent …
Jet substructure has emerged as a critical tool for LHC searches, but studies so far have relied heavily on shower Monte Carlo simulations, which formally approximate QCD at leading-log level. We demonstrate that systematic higher-order QCD computations of jet substructure can be carried out by boosting global event shapes by a large momentum Q, and accounting for effects due to finite jet size, initial-state radiation (ISR), and the underlying event (UE) as 1/Q corrections. In particular, we compute the 2-subjettiness substructure distribution for boosted Z -> q qbar events at the LHC at next…
Weak boson fusion is a copious source of intermediate mass Higgs bosons at the LHC. The additional very energetic forward jets in these events provide for powerful background suppression tools. We analyze the $H \to ττ$ decay mode for the Standard Model Higgs boson. A parton level analysis of the dominant physics backgrounds (mainly $Z \to ττ$ and Drell-Yan production of $τ$'s) and of reducible backgrounds (from $W+$ jet and $b\bar{b}$ production in association with two jets and subsequent leptonic decays) demonstrates that this channel allows the observation of $H \to ττ$ in a low background …
We discuss the feasibility of the observation of the signal from $B_c$ mesons in the ATLAS experiment at the LHC. In particular, we address the decay mode $B_c{\rightarrow}J/ψπ$ followed by the leptonic decay $J/ψ{\rightarrow}μ^+μ^-$, which should permit an accurate measurement of the $B_c$ mass. We performed a Monte Carlo study of the signal and background concluding that a precision of $\approx$ 1 MeV for the $B_c$ mass could be achieved after one year of running at $\lq\lq$low" luminosity. The semileptonic decay $B_c{\rightarrow}J/ψ μ^+ν_μ$ is also considered for a possible extraction of ${…
We study high-pt jets from QCD and from highly-boosted massive particles such as tops, W, Z and Higgs, and argue that infrared-safe observables can help reduce QCD backgrounds. Jets from QCD are characterized by different patterns of energy flow compared to the products of highly-boosted heavy particle decays, and we employ a variety of jet shapes, observables restricted to energy flow within a jet, to explore this difference. Results from Monte Carlo generators and arguments based on perturbation theory support the discriminating power of the shapes we refer to as planar flow and angularities…
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These lectures on Higgs boson collider searches were presented at TASI 2006. I first review the Standard Model searches: what LEP did, prospects for Tevatron searches, the program planned for LHC, and some of the possibilities at a future ILC. I then cover in-depth what comes after a candidate discovery at LHC: the various measurements one has to make to determine exactly what the Higgs sector is. Finally, I discuss the MSSM extension to the Higgs sector.
The possibility to simulate lepton number violating supersymmetric models has been introduced into the recently updated PYTHIA event generator, now containing 1278 decay channels of SUSY particles into SM particles via lepton number violating interactions. This generator has been used in combination with the ATLFAST detector simulation to study the impact of lepton number violation (LV) on event topologies in the ATLAS detector, and trigger menus designed for LV-SUSY are proposed based on very general considerations. In addition, a rather preliminary analysis is presented on the possibility fo…
Heavy long-lived multi-charged leptons (MCLs) are predicted by various new physics models. These hypothetical MCLs can form bound states, due to their high electric charges and long life times. In this work, we propose a novel strategy of searching for MCLs through their bound state productions and decays. By utilizing LHC-8 TeV data in searching for resonances in the diphoton channel, we exclude the masses of isospin singlet heavy leptons with electric charge $|q|\geq 6$ (in units of electron charge) lower than $\sim$1.2 TeV, which are much stronger than the corresponding 8 TeV LHC bounds fro…
We discuss the search for the heavy charged Higgs bosons H^\pm, implicitly of the Minimal Supersymmetric Standard Model, in the tau-nu decay mode at the LHC. Compared to the dominant decay mode H^\pm\to bt, the channel suffers from suppression due to the branching ratio and the lack of direct mass reconstruction, but the reduced QCD background makes it a feasible channel especially in the large tan(beta) region. We study the production in `bt fusion' via bg\to tH^-, and the leading irreducible background bg\to tW^-. Our results indicate that for the H^\pm mass of greater than 200 GeV and up to…
