Weak interactions in neutron $β$-decay exhibit parity violation through the preferential emission of right-handed antineutrinos. We identify this symmetry breaking with a reduction of phase space due to the small neutrino mass. During a brief interval of momentum exchange, a small mass neutrino puts the emission process close to the bifurcation horizon of Rindler space, doubly covered by Minkowski space ${\cal M}$ as dictated by the Equivalence Principle of general relativity. In the limit of arbitrarily small mass, this two-sheet covering effectively collapses into a single sheet, reducing the dimension of Dirac spinors from four to two, leaving neutrinos single-handed. This predicts a similar reduction to single-handed particle states in electrons created at TeV energies, which may be tested with the planned linear leptonic colliders. If confirmed, right-handed small mass neutrinos are expected to exist at sufficiently low energies.
Prospects for Observing an Invisibly Decaying Higgs Boson in $t\bar{t}H$ Production at the LHC
在这篇论文中，我们研究了在大型强子对撞机的相关$t\bar tH$产生中观测到不可见衰变的希格斯玻色子的前景。信号和背景过程的蒙特卡罗模拟结果表明，有可能观测到发现所需的统计上显著数量的信号事件。此外，可以进一步改进分析以减少$W$玻色子的错误重建的数量。$t \bar t H$产生的分析与希格斯玻色子衰变到不可见通道的模型无关。对于$H\to invisible$可能感兴趣的模型，有几种可能性。在这篇论文中，我们研究了最简单的超对称模型，称为mSUGRA。对mSUGRA模型参数空间的扫描结果表明，最轻的中性希格斯玻色子与最轻的中性伴子对的分支比高的区域被目前的实验限制所排除。$h \to b \bar b$通道占主导地位，并且在该通道中发现的可能性不会被不可见的衰变抑制。这一结果并不排除不可见信道作为其他模型中可能的签名的可能性。本论文的第四章是在B. P. Kersevan，\underline{M. Malawski}，E.里希特-瓦斯：{ \em Prospects for observing an invisibly decaying希格斯玻色子in the $t\bar t H$ production at the LHC}，The European Physical Journal C-Particles and Fields，2003，vol. 29，no. 4，p…
We study the production and decay of a light charged Higgs boson at the future Large Hadron electron Collider (LHeC) in the framework of the Two Higgs Doublet Type III, assuming a four-zero texture in the Yukawa matrices and a general Higgs potential. We analyze the charge current production processes $e^- p \to ν_e q H^+ $ considering the signature $H^+ \to c \bar{b} + c.c.$ of the final state. We take this signature and we compare it to the irreducible background from Standard Model (SM) interactions. We consider scenarios of the model which are consistent with current experimental data from…
We study the prospects for observing double parton scattering through four-muon final states, forming two opposite-sign muon pairs, in the LHCb experiment in pp collisions at 14 TeV centre of mass energy. We consider two special cases, namely double Drell-Yan and J/psi-pair production. The kinematic properties and prospects for observing these processes are discussed. We find that the production rate depends strongly on the origin of the four muons, while many kinematic properties can be used to help identify the presence of double parton scattering events.
We show that in a two Higgs doublet model type-II extended by vectorlike leptons the contributions from heavy neutral and charged Higgs bosons to the anomalous magnetic moment of the muon simultaneously feature chiral enhancement from masses of new leptons and $\tan^2 β$ enhancement from couplings of Higgs bosons. Assuming moderate values of new Yukawa couplings, not exceeding one, that can remain perturbative to very high energy scales, the measured value of muon $g-2$ can be explained within one standard deviation even with 6.5 TeV leptons or 20 TeV Higgs bosons. Allowing new couplings near …
Vectorlike leptons are an intriguing possibility for physics beyond the Standard Model. We study the reach for discovering (at 5$σ$ significance) or excluding (at 95 per cent confidence) models of charged vectorlike leptons that mix predominantly with the tau, using multi-lepton signatures at various future proton-proton collider options: a high-luminosity LHC with $\sqrt{s} =$ 14 TeV, a high-energy LHC with $\sqrt{s} =$ 27 TeV, and possible new longer-tunnel colliders with $\sqrt{s} =$ 70 or 100 TeV. For weak isodoublet vectorlike leptons, we estimate that a 27 TeV high-energy LHC with 15 ab$…
We discuss the prospects of studying lepton number violating processes in order to identify Majorana neutrinos from low scale seesaw mechanisms at lepton-proton colliders. In particular, we consider the scenarios of colliding electrons with LHC energy protons and, motivated by the efforts towards the construction of a muon collider, the prospects of muon-proton collisions. We find that present constraints on the mixing of the Majorana neutrinos still allow for a detectable signal at these kind of facilities given the smallness of the Standard Model background. We discuss possible cuts in order…
In light of the recent IceCube evidence for a flux of extraterrestrial neutrinos, we revisit the prospect of observing the sources of the Galactic cosmic rays. In particular, we update the predictions for the neutrino flux expected from sources in the nearby star-forming region in Cygnus taking into account recent TeV gamma ray measurements of their spectra. We consider the three Milagro sources: MGRO J2019+37, MGRO J1908+06 and MGRO J2031+41 and calculate the attainable confidence level limits and statistical significance as a function of the exposure time. We also evaluate the prospects for …
Sensitivity prospects for lepton-trijet signals in the $ν$SMEFT at the LHeC
Instituto de Física de Mar del Plata (IFIMAR) CONICET, UNMDP（马德普拉塔物理研究所 (IFIMAR) 阿根廷国家科学研究委员会，马德普拉塔国立大学）；Instituto de Física La Plata (IFLP) CONICET, UNLP（拉普拉塔物理研究所 (IFLP) 阿根廷国家科学研究委员会，拉普拉塔国立大学）；Instituto de Física, Facultad Ingeniería, Universidad de la República（共和国大学工程学院物理研究所）；Departamento de Física, Universidad Nacional de Mar del Plata（马德普拉塔国立大学物理系）；Instituto de Física, Facultad de Ciencias, Universidad de la República（共和国大学理学院物理研究所）
One of the primary goals of the Large Hadron Collider is to understand the electroweak symmetry breaking mechanism. In the Standard Model, electroweak symmetry breaking is described by the Higgs mechanism which includes a scalar Higgs boson. Electroweak measurements constrain the Standard Model Higgs boson mass to be in the 114.4 to 157 GeV/c^2 range. Within this mass window, the Higgs predominantly decays into two b-quarks. As such, we investigate the prospect of observing the Standard Model Higgs decaying to b\bar{b} produced in weak-boson-fusion with an associated central photon. An isolate…
Bi-large patterns for the leptonic mixing matrix are confronted with current neutrino oscillation data. We analyse the status of these patterns and determine, through realistic simulations, the potential of upcoming long-baseline experiment DUNE in testing bi-large \emph{ansatze} and discriminating amongst them.
We study the prospects for excluding or discovering vectorlike leptons using multilepton events at the LHC. We consider models in which the vectorlike leptons decay to tau leptons. If the vectorlike leptons are weak isosinglets, then discovery in multilepton states is found to be extremely challenging. For the case that the vectorlike leptons are weak isodoublet, we argue that there may be an opportunity for exclusion for masses up to about 275 GeV by direct searches with existing LHC data at sqrt{s}=8 TeV. We also discuss prospects for exclusion or discovery at the LHC with future sqrt{s}=13 …
After the observation of non-zero $θ_{13}$ the goal has shifted to observe $CP$ violation in the leptonic sector. Neutrino oscillation experiments can, directly, probe the Dirac $CP$ phases. Alternatively, one can measure $CP$ violation in the leptonic sector using Leptonic Unitarity Quadrangle(LUQ). The existence of Standard Model (SM) gauge singlets - sterile neutrinos - will provide additional sources of $CP$ violation. We investigate the connection between neutrino survival probability and rephasing invariants of the $4\times4$ neutrino mixing matrix. In general, LUQ contain eight geometri…
The apparent tensions emerging from the comparison of experimental data of the anomalous magnetic moments of the muon and electron to the Standard Model predictions ($Δa_{μ,e}$) could be interpreted as a potential signal of New Physics. Models encompassing a light vector boson have been known to offer a satisfactory explanation to $Δa_μ$, albeit subject to stringent experimental constraints. Here we explore a minimal extension of the Standard Model via a leptophilic vector boson $Z^\prime$, under the hypothesis of strictly flavour-violating couplings of the latter to leptons. The most constrai…
The Higgs boson pair production at a linear $e^+e^-$ collider is analyzed in the $4τ$ final state in the context of lepton-specific or type IV 2HDMs. Both beams are assumed to be unpolarized. The Higgs boson pairs (HA) are produced through off-shell $Z^*$ production and decay to $τ$-jets which is the main decay channel for neutral Higgs bosons in type IV. Using a simplified detector simulation based on SiD detector at ILC, the 4$τ$ signal is studied through the $τ$-jet pair invariant mass reconstruction. Several benchmark scenarios are considered for center of mass energies of 500 and 1000 GeV…
The $WW$ production is the primary channel to directly probe the triple gauge couplings. We first analyze the $e^+ e^- \rightarrow W^+ W^-$ process at the future lepton collider, China's proposed Circular Electron-Positron Collider (CEPC). We use the five kinematical angles in this process to constrain the anomalous triple gauge couplings and relevant dimension six operators at the CEPC up to the order of magnitude of $10^{-4}$. The most sensible information is obtained from the distributions of the production scattering angle and the decay azimuthal angles. We also estimate constraints at the…
We discuss the future prospects of heavy neutrino searches at next generation lepton colliders. In particular, we focus on the planned electron-positron colliders, operating in two different beam modes, namely, $e^+e^-$ and $e^-e^-$. In the $e^+e^-$ beam mode, we consider various production and decay modes of the heavy neutrino ($N$), and find that the final state with $e+2j+{E\!\!\!/}_T$, arising from the $e^+e^-\to Nν$ production mode, is the most promising channel. However, since this mode is insensitive to the Majorana nature of the heavy neutrinos, we also study a new production channel $…
The kaon sector is characterised by several processes which are under active investigation across different experiments. In this work, we present the global picture that emerges from a study of the different decay modes. We begin by revisiting the theoretical component of these decays and providing up-to-date predictions of the Standard Model as well as the corresponding uncertainties. Several new features emerge, in particular for $K_{S,L}\to μ\barμ$, and are presented in considerable detail. This offers an ideal platform for extracting the parameter space supported by the existing data. Moti…
Composite Higgs models feature new strong dynamics leading to the description of the Higgs boson as a bound state arising from the breaking of a global (flavour) symmetry. These models generally include light states generated by the same dynamics, the detection of which may present the first observable signs of compositeness. One such state is a pseudo-scalar boson resulting from the breaking of a $U(1)$ symmetry common to most composite setups, and whose hints are expected to be visible through low-mass resonance searches at present and future hadron and lepton colliders. In this work we stud…
The type II seesaw mechanism is an attractive way to generate the observed light neutrino masses. It postulates a SU(2)$_\mathrm{L}$-triplet scalar field, which develops an induced vacuum expectation value after electroweak symmetry breaking, giving masses to the neutrinos via its couplings to the lepton SU(2)$_\mathrm{L}$-doublets. When the components of the triplet field have masses around the electroweak scale, the model features a rich phenomenology. We discuss the current allowed parameter space of the minimal low scale type II seesaw model, taking into account all relevant constraints, i…
We investigate the prospects for discovering charginos and neutralinos at a future $pp$ collider with $\sqrt{s} = 100$ TeV. We focus on models where squarks and sleptons are decoupled -- as motivated by the LHC data. Our initial study is based on models where Higgsinos form the main component of the LSP and $W$-inos compose the heavier chargino states ($M_2 > μ$), though it is straightforward to consider the reverse situation also. We show that in such scenarios $W$-inos decay into $W^\pm$, $Z$ and $h$ plus neutralinos almost universally. In the $W Z$ channel we compare signal and background i…
There exist candidates for the negative-parity states $Λ_{c,b}(1/2^-, 3/2^-)$ consisting of an isospin-zero, spin-zero light diquark $[ud]$ with one unit of orbital angular momentum with respect to a $c,b$ quark. However, there exists only one candidate for the orbital excitations of the $Σ_c(1/2^+)$ and $Σ_c^*(3/2^+)$, and none for the orbital excitations of $Σ_b(1/2^+)$ or $Σ_b^*(3/2^+)$. We extend a previous discussion of odd-parity $Λ_{c,b}$ states and explore some patterns of the odd-parity $Σ_{c,b}$ baryons consisting of a light isospin-one nonstrange diquark $(uu,ud,dd)$ in a state of $…
Prospects for toponium formation at the LHC in the single-lepton mode
Sorbonne Université et CNRS（索邦大学与法国国家科学研究中心）；KEK Theory Center（高能加速器研究机构理论中心）；Xi’an University of Architecture and Technology（西安建筑科技大学）；The University of Osaka（大阪大学）
Single top quark production through weak interactions is considered to be an important source of charged Higgs in the Minimal Super Symmetric Standard Model. In the s-channel single top production having largest cross-section may appear as a propagator in the form of heavy resonance state decaying to a pair of top and bottom quark. The process under investigation is $pp \rightarrow H^{\pm}\rightarrow tb \rightarrow b\bar{b}W^{\pm} \rightarrow b\bar{b}τ^{\pm} ν_τ$, where top quark exclusively decays into a pair of bottom quark and W boson while W boson subsequently decays to $τ$ jet and neutrin…
We examine the prospects for the detection of Higgs mediated lepton flavor violation at LHC and at a photon collider in the minimal supersymmetric standard model with large lepton flavor violating mass insertions in the $μ-τ$ sector constraining the parameter space with several experimental bounds. We find rates probably too small to be observed at future experiments if models have to accommodate for a neutralino relic density as measured by WMAP and explain the $(g-2)_μ$ anomaly: better prospects are found if these two constraints are applied only as upper bounds. The spin-independent neutral…
We investigate the prospects of discovering split Supersymmetry at a future 100 TeV proton-proton collider through the direct production of electroweakino next-to-lightest-supersymmetric-particles (NLSPs). We focus on signatures with multi-lepton and missing energy: $3\ell$, opposite-sign dileptons and same-sign dileptons. We perform a comprehensive study of different electroweakino spectra. A 100 TeV collider with 3000/fb data is expected to exclude Higgsino thermal dark matter candidates with $m_{\rm{LSP}}\sim 1 $ TeV if Wino NLSPs are lighter than about 3.2 TeV. The $3\ell$ search usually o…
We have studied the prospects of measuring the CP violating phase with atmospheric neutrinos at a large magnetized iron calorimeter detector considering the muons (directly measurable) of the neutrino events generated by a MonteCarlo event generator Nuance. The effect of $θ_{13}$ and $δ_{CP}$ appears dominantly neither in atmospheric neutrino oscillation nor in solar neutrino oscillation, but appears as subleading in both cases. These are observable in range of $E \sim 1$ GeV for atmospheric neutrino, where solar and atmospheric oscillation couple. In this regime, the quasi-elastic events domi…
We explore the potential of the CERN Large Hadron Collider to access a strongly interacting electroweak symmetry breaking sector via weak boson scattering with WWjj, ZZjj and WZjj final states. As examples of models with scalar or vector resonances we concentrate on a scenario with a heavy Higgs boson and on a Warped Higgsless Kaluza-Klein model of narrow spin-one resonances. The signal and the most prominent background processes are evaluated using exact tree-level matrix elements including full off-shell and finite width effects for final states with two tagging jets and four leptons. Using …
We demonstrate the ability to measure the CP-phase of a Higgs boson state by looking at the decays of heavy, Majorana neutrinos in the process $pp \to H \to N N$ at the LHC. This is shown for signals with both opposite-sign ($l^{\pm} l^{\mp} W^{\pm} W^{\mp}$) and same-sign ($l^{\pm} l^{\pm} W^{\mp} W^{\mp}$) leptonic final states. These signals are investigated in the general framework of a sequential fourth generation of fermions with an additional right-handed neutrino. Such a scenario would naturally give rise to heavy Majorana neutrinos as well as significant enhancements to Higgs producti…
Composite Higgs models predict the existence of resonances. We study in detail the collider phenomenology of both the vector and fermionic resonances, including the possibility of both of them being light and within the reach of the LHC. We present current constraints from di-boson, di-lepton resonance searches and top partner pair searches on a set of simplified benchmark models based on the minimal coset $SO(5)/SO(4)$, and make projections for the reach of the HL-LHC. We find that the cascade decay channels for the vector resonances into top partners, or vice versa, can play an important rol…
The long-standing anomaly in the anomalous magnetic moment of the muon indicates the presence of chirality violating new physics contributions. A possible solution involves scalar leptoquarks with left- and right-handed couplings to the top quark. Two such representations of scalar leptoquarks exist for which the contribution to $(g-2)_μ$ can possess an $m_t/m_μ$ enhancement compared to the Standard Model. The leptoquarks also induce loop corrections to $Z$ couplings to muons which probe as well new physics contributions which possess sources of $SU(2)$ symmetry breaking and we find that this …
Two types of pseudoscalar quarkonium electromagnetic decay processes, i.e. decay to a lepton pair, and to a lepton pair plus a photon (Dalitz decay), are analyzed at the leading order in NRQCD expansion. The former type of processes, highly suppressed in the Standard Model, have been hoped to act as the sensitive probes of the possible new physics. The latter type of processes generally possess much greater decay rates than the former, owing to several conspiring factors. The recently launched BES-III program, with $10^8$ $η_c$ samples to be anticipated in the coming years, may be able to obse…
I will briefly discuss the signatures and discovery prospects of several new physics models containing dark matter candidates at future lepton colliders. In particular, I will discuss the two models that, among other signatures, lead to electroweak gauge bosons and missing energy: the Inert Doublet Model, as well as the THDMa, a two Higgs doublet model with an additional pseudoscalar that serves as a portal to the dark sector. Results are mainly based on a Snowmass Whitepaper arXiv:2203.07913
Many Standard Model extensions can contribute to four-lepton signals at large colliders. We review the particular case of leptophilic interactions eventually observable at the LHC and the ILC, paying special attention to the addition of a new vector boson coupled to muon minus tau lepton number, $Z'_{μ- τ}$, and emphasizing the prospects at a very large hadron collider with $\sqrt s =$ 100 TeV. We also discuss in this case the new contribution to two-lepton (Drell-Yan) production when the new leptophilic interaction has a non-vanishing kinetic mixing with the SM.
We study the lepton-induced resonant production of color-adjoint leptons (leptogluons) at the LHC employing the lepton parton density function of the proton. We demonstrate that this production mechanism can be useful to extend the LHC ability to search for leptogluons beyond purely quark/gluon initiated production processes up to ~ 3.5 TeV leptogluon masses and O(1) TeV compositeness scales. Discerning leptogluons from scalar and vector leptoquarks is also possible in this channel, given a data sample containing the order of 100 signal events. We argue that the resonant channel can be combine…
