Search

I review possible signals at hadron colliders of bileptons, namely doubly charged vectors or scalars with lepton number L = ± 2 , as predicted by a 331 model, based on a S U (3) c × S U (3) L × U (1) X symmetry. In particular, I account for a version of the 331 model wherein the embedding of the hypercharge is obtained with the addition of three exotic quarks and vector bileptons. Furthermore, a sextet of S U (3) L , necessary to provide masses to leptons, yields an extra scalar sector, including a doubly charged Higgs, i.e., scalar bileptons. As bileptons are mostly produced in pairs at hadron colliders, their main signal is provided by two same-sign lepton pairs at high invariant mass. Nevertheless, they can also decay according to non-leptonic modes, such as a TeV-scale heavy quark, charged 4/3 or 5/3, plus a Standard Model quark. I explore both leptonic and non-leptonic decays and the sensitivity to the processes of the present and future hadron colliders. [ABSTRACT FROM AUTHOR]

The minimal vector dark matter is a viable realization of the minimal dark matter paradigm. It extends the standard model by the inclusion of a vector matter field in the adjoint representation of SU (2) L . The dark matter candidate corresponds to the neutral component of the new vector field ( V 0 ). Previous studies have shown that the model can explain the observed dark matter abundance while evading direct and indirect searches. At colliders, the attention has been put on the production of the charged companions of the dark matter candidate. In this work, we focus on the mono-Higgs and mono-Z signals at Hadron colliders. The new charged vectors ( V ± ) are invisible unless a dedicated search is performed. Consequently, we assume that the mono-Higgs and mono-Z processes correspond to the p p → h V + , 0 V − , 0 and p p → Z V + , 0 V − , 0 reactions, respectively. We show that, while the p p → h V + , 0 V − , 0 is more important, both channels may produce significant signals at the HL-LHC and colliders running at s = 27 TeV and 100 TeV, probing almost the complete parameter space. [ABSTRACT FROM AUTHOR]

Radiation damage significantly impacts the performance of silicon tracking detectors in Large Hadron Collider (LHC) experiments such as ATLAS and CMS, with signal reduction being the most critical effect; adjusting sensor bias voltage and detection thresholds can help mitigate these effects, generating simulated data that accurately mirror the performance evolution with the accumulation of luminosity, hence fluence, is crucial. The ATLAS and CMS collaborations have developed and implemented algorithms to correct simulated Monte Carlo (MC) events for radiation damage effects, achieving impressive agreement between collision data and simulated events. In preparation for the high-luminosity phase (HL-LHC), the demand for a faster ATLAS MC production algorithm becomes imperative due to escalating collision, events, tracks, and particle hit rates, imposing stringent constraints on available computing resources. This article outlines the philosophy behind the new algorithm, its implementation strategy, and the essential components involved. The results from closure tests indicate that the events simulated using the new algorithm agree with fully simulated events at the level of few %. The first tests on computing performance show that the new algorithm is as fast as it is when no radiation damage corrections are applied. [ABSTRACT FROM AUTHOR]

By extending the dipole Pomeron (DP) model, successful in describing elastic nucleon–nucleon scattering, to proton single diffractive dissociation (SD), we predict a dip-bump structure in the squared four-momentum transfer (t) distribution of proton's SD. Structures in the t distribution of single diffractive dissociation are predicted around t = − 4 GeV 2 at LHC energies in the range of 3 GeV 2 ≲ | t | ≲ 7 GeV 2 . Apart from the dependence on s (total energy squared) and t (squared momentum transfer), we predict also a dependence on missing masses. We include the minimum set of Regge trajectories, namely the Pomeron and the Odderon, indispensable at the LHC. Further generalization, e.g., by the inclusion of non-leading Regge trajectories, is straightforward. The present model contains two types of Regge trajectories: those connected with t -channel exchanges (the Pomeron, the Odderon, and non-leading (secondary) reggeons) appearing at small and moderate − t , where they are real and nearly linear, as well as direct-channel trajectories α (M 2) related to missing masses. In this paper, we concentrate on structures in t neglecting (for the time being) resonances in M 2 . [ABSTRACT FROM AUTHOR]

I review possible signals at hadron colliders of bileptons, namely doubly charged vectors or scalars with lepton number L=±2, as predicted by a 331 model, based on a SU(3)c×SU(3)L×U(1)X symmetry. In particular, I account for a version of the 331 model wherein the embedding of the hypercharge is obtained with the addition of three exotic quarks and vector bileptons. Furthermore, a sextet of SU(3)L, necessary to provide masses to leptons, yields an extra scalar sector, including a doubly charged Higgs, i.e., scalar bileptons. As bileptons are mostly produced in pairs at hadron colliders, their main signal is provided by two same-sign lepton pairs at high invariant mass. Nevertheless, they can also decay according to non-leptonic modes, such as a TeV-scale heavy quark, charged 4/3 or 5/3, plus a Standard Model quark. I explore both leptonic and non-leptonic decays and the sensitivity to the processes of the present and future hadron colliders.

At high-energy accelerator facilities like the ones that are part of the accelerator complex at the European Organization for Nuclear Research (CERN), Monte Carlo radiation transport codes are widely employed to face the challenges of estimating radionuclide production yields and activities with the aim of performing the radiological characterization of activated components. Indeed, it is of paramount importance to ensure adequate radiation protection during scheduled maintenance, transport, and handling of these components and to establish their proper disposal pathway once they ultimately reach the end of their useful life. This paper summarizes the principles of the fluence conversion coefficients method that was developed as a complementary approach for radiological characterization studies. Then, the Monte Carlo simulations in preparation to the pilot beam run at the Large Hadron Collider at CERN in 2021 are presented as a practical example of possible applications. Finally, the flexibility of the method and the most relevant operational radiation protection implications are discussed in relation to the provided example. [ABSTRACT FROM AUTHOR]

This article reviews the most recent measurements of B (s) 0 → μ+μ− decay properties at the Large Hadron Collider (LHC) which are the most precise to date. The measurements of the branching fraction and effective lifetime of the B s 0 → μ+μ− decay by the ATLAS, CMS, and LHCb collaborations, as well as the search for B 0 → μ+μ− decays, are summarized with a focus on the experimental challenges. Furthermore, prospects are given for these measurements and new observables that become accessible with the foreseen amounts of data by the end of the LHC. [ABSTRACT FROM AUTHOR]

The exclusive photo‐ and electroproduction of light vector mesons like ρ,ω,$$ \rho, \omega, $$ and ϕ$$ \phi $$ is studied in γp$$ \gamma p $$ collisions within the color dipole formalism with vector meson wave functions obtained using the AdS/QCD holographic approach. This setup provides a good description of the existing data for the ground vector mesons ρ(1S),ω(1S),andϕ(1S)$$ \rho (1S),\kern0.3em \omega (1S),\kern0.3em \mathrm{and}\kern0.3em \phi (1S) $$ and permits us to make predictions for the corresponding excited states. The results show significant theoretical uncertainties related to modeling the partial dipole amplitude, which can be constrained with upcoming measurements in future hadron colliders. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Charged hadron fragmentation functions from collider data: NNPDF Collaboration." The correction addresses an error in the implementation of the rapidity range for the ALICE data included in the study. The error resulted in an incorrect rapidity range, but the impact on the conclusions of the study is reported to be marginal. The correction notice provides details about the error and its correction, as well as the impact on the figures and tables presented in the original article. The text provides a table and several graphs related to the momentum fraction for different types of particles. It also mentions an updated and corrected set of data available through LHAPDF. The authors express gratitude to Aleksas Mazeliauskas for their contributions. The graphs compare different sets of data and show the correlation coefficient, differential cross sections, and theoretical predictions. The purpose of the text is to present and analyze the data, without making any judgments or conclusions. [Extracted from the article]

At the Large Hadron Collider (LHC), absolute luminosity calibrations obtained by the van der Meer (vdM) method are affected by the mutual electromagnetic interaction of the two beams. The colliding bunches experience relative orbit shifts, as well as optical distortions akin to the dynamic- β effect, that both depend on the transverse beam separation and must therefore be corrected for when deriving the absolute luminosity scale. In the vdM regime, the beam–beam parameter is small enough that the orbit shift can be calculated analytically. The dynamic- β corrections to the luminometer calibrations, however, had until the end of Run 2 been estimated in the linear approximation only. In this report, the influence of beam–beam effects on the vdM-based luminosity scale is quantified, together with the associated systematic uncertainties, by means of simulations that fully take into account the non-linearity of the beam–beam force, as well as the resulting non-Gaussian distortions of the transverse beam distributions. Two independent multiparticle simulations, one limited to the weak-strong approximation and one that models strong-strong effects in a self-consistent manner, are found in excellent agreement; both predict a percent-level shift of the absolute pp-luminosity values with respect to those assumed until recently in the physics publications of the LHC experiments. These results also provide guidance regarding further studies aimed at reducing the beam–beam-related systematic uncertainty on beam–beam corrections to absolute luminosity calibrations by the van der Meer method. [ABSTRACT FROM AUTHOR]

We consider the class of inclusive hadron collider processes in which one or more energetic jets are produced, possibly accompanied by colourless particles. We provide a general formulation of a slicing scheme for this class of processes, by identifying the various contributions that need to be computed up to next-to-leading order (NLO) in QCD perturbation theory. We focus on two novel observables, the one-jet resolution variable ∆Et and the n-jet resolution variable k T ness , and explicitly compute all the ingredients needed to carry out NLO computations using these variables. We contrast the behaviour of these variables when the slicing parameter becomes small. In the case of k T ness we also present results for the hadroproduction of multiple jets. [ABSTRACT FROM AUTHOR]

We present a systematic formalism based on a factorization theorem in soft-collinear effective theory to describe non-global observables at hadron colliders, such as gap-between-jets cross sections. The cross sections are factorized into convolutions of hard functions, capturing the dependence on the partonic center-of-mass energy s ̂ , and low-energy matrix elements, which are sensitive to the low scale Q0 ≪ s ̂ characteristic of the veto imposed on energetic emissions into the gap between the jets. The scale evolution of both objects is governed by a renormalization-group equation, which we derive at one-loop order. By solving the evolution equation for the hard functions for arbitrary 2 → M jet processes in the leading logarithmic approximation, we accomplish for the first time the all-order resummation of the so-called "super-leading logarithms" discovered in 2006, thereby solving an old problem of quantum field theory. We study the numerical size of the corresponding effects for different partonic scattering processes and explain why they are sizable for pp → 2 jets processes, but suppressed in H/Z and H/Z + jet production. The super-leading logarithms are given by an alternating series, whose individual terms can be much larger than the resummed result, even in very high orders of the loop expansion. Resummation is therefore essential to control these effects. We find that the asymptotic fall-off of the resummed series is much weaker than for standard Sudakov form factors. [ABSTRACT FROM AUTHOR]

Energy correlators measured inside high-energy jets at hadron colliders have recently been demonstrated to provide a new window into both perturbative and non-perturbative Quantum Chromodynamics. A number of the most interesting features of these correlators, namely their universal scaling behavior and the ability to image the confinement transition, require precise angular resolution, necessitating the use of tracking information in experimental measurements. Theoretically, tracking information can be incorporated into the energy correlators using track functions, which are non-perturbative functions describing the fragmentation of quarks and gluons into charged hadrons. In this paper, we apply our recently developed track function formalism to energy correlators, and study in detail the interplay of track functions with perturbative resummation and non-perturbative power corrections. We provide resummed results for the energy correlators at collinear next-to-leading-logarithmic accuracy and compare with parton shower Monte Carlo simulations. For the two-point correlator the use of tracking has a minimal effect throughout the entire distribution, but it has a significant effect for higher point correlators. Our results are crucial for the theoretical interpretation of recent experimental measurements of the energy-energy correlators. [ABSTRACT FROM AUTHOR]

Relevance and formulation of the problem. The number of areas of scientific and practical activity in which it is necessary to consider relativistic corrections is steadily growing. In many cases, two objects under study move towards one another. This takes place both in relation to astronomical objects and in relation to quantum particles, including in colliders—accelerators of charged particles in colliding beams. With counter relativistic motions, the relative velocity does not coincide with the approach velocity. However, considering relative velocity alone limits the arsenal of research tools and methods. As opposed to relative velocity, which is determined in accordance with the relativistic formula for velocity addition, the approach velocity of unaccelerated objects is defined as the ratio of the distance between them to the time it takes to cover it. The purpose of this work is to analyze the variety of the relativistic approach velocity of objects depending on the choice of inertial reference frames based on the data of the Large Hadron Collider. Results. At the Large Hadron Collider, the approach velocity of protons is almost twice as high as the speed of light in the laboratory reference frame. In frames of reference associated with moving protons, depending on the options of relativistic transformation of segments of lengths and time intervals, the maximum approach velocity of protons is 1.1 × 108с, and the minimum is 1.2 m/s. In accordance with the technique based on the relativistic velocity addition formula, the approach velocity in reference systems associated with moving protons is almost equal to the speed of light. In this case, the approach velocity becomes equal to the relative velocity, which should not be considered as a generalization of the classical mechanics rule on the indistinguishability of these velocities to relativistic mechanics. Practical significance. The results obtained may be of interest in assessing the approach velocities of astronomical objects, including the Earth and asteroids, as well as significantly expand the variability of hypotheses when processing experimental data arrays obtained at elementary particle accelerators, including the Large Hadron Collider. [ABSTRACT FROM AUTHOR]

We extend heavy Higgs searches at the Large Hadron Collider for H → τ μ by CMS, and H → τ τ by ATLAS and CMS, to study discovery prospects of extra Higgs states in p p → H , A → τ μ , τ τ with and final states, where j τ = π , ρ , a 1 and is missing transverse energy. In a general two Higgs doublet model without Z 2 symmetry, extra Yukawa couplings ρ τ τ and ρ τ μ can drive H , A → τ τ and τ μ channels at hadron colliders, following gluon–gluon fusion production with extra ρ tt couplings. The light Higgs boson h(125) is found to resemble closely the Standard Model Higgs boson; in the alignment limit of cos γ → 0 for h–H mixing, flavor changing neutral Higgs couplings such as h → τ μ are naturally suppressed, but the couplings of the heavier H is optimized by sin γ → 1 . We define various signal regions for H , A → τ μ and τ τ and evaluate physics backgrounds from dominant processes with realistic acceptance cuts and tagging efficiencies. Two different studies are presented. We first perform a parton level study without any hadronization and with minimal detector smearing. We then include hadronization using PYTHIA 8.2 and fast detector simulation using DELPHES to give event level simulation. Results for s = 13 TeV appear promising, which we extend further to s = 14 TeV for the High Luminosity LHC. [ABSTRACT FROM AUTHOR]

The Large Hadron Collider (LHC) stores two high-energy counter-rotating particle beams consisting of multiple bunches of a nanosecond length. Precise knowledge of the number of particles within each bunch, known as the bunch intensity, is crucial for physicists and accelerator operators. From the very beginning of the LHC operation, bunch intensity was measured by four commercial fast beam current transformers (FBCTs) coupling to the beam current. However, the FBCTs exhibited several shortcomings which degraded the measurement accuracy below the required level. A new sensor, the wall current transformer (WCT), has been developed to overcome the FBCT limitations. The WCT consists of eight small radio frequency (RF) current transformers distributed radially around the accelerator's vacuum chamber. Each transformer couples to a fraction of the image current induced on the vacuum chamber by the passing particle beam. A network of RF combiners sums the outputs of all transformers to produce a single signal which, after integration, is proportional to the bunch intensity. In laboratory tests and during beam measurements, the WCT performance was demonstrated to convincingly exceed that of the FBCT. All originally installed FBCTs were replaced by four WCTs, which have been serving as the LHC reference bunch intensity sensors since 2016. [ABSTRACT FROM AUTHOR]

Strange hadron transverse momentum spectra are analyzed in symmetric p p and P b P b and asymmetric p P b collision systems for their dependence on rapidity and event charged-particle multiplicity. The thermodynamically consistent Tsallis models with and without flow velocity are used to reproduce the experimental data, extracting the freeze-out parameters to gain insights into the underlying physics of the collision processes by looking into the parameters change with different multiplicities, particle types, and collision geometries. We found that with an increase in the event multiplicity, the average transverse flow velocity, effective, and kinetic freezeout temperatures increase, with heavier strange particle species exhibiting a more significant increase. The value of the non-extensivity parameter decreases with an increase in the multiplicity of the particles. For heavier particles, larger T e f f and T 0 and smaller q have been observed, confirming the quick thermalization and equilibrium for massive particles. Furthermore, the differences in parameter values for particle species are more significant in p p and p P b collisions than in P b P b collisions. In addition, in symmetric p p and P b P b collisions, parameter values ( q , T 0 , β T ) show more significant shifts for heavier particles compared to the lighter ones. In contrast, in asymmetric p P b collisions, both heavier and lighter particles display uniform linear progression. [ABSTRACT FROM AUTHOR]

This paper presents an overview of Monte Carlo (MC) event generators for simulation of proton-proton collisions along with the results on hadron production at nuclotron-based ion collider facility (NICA) energies. Namely, mean multiplicities, mean transverse momenta, and rapidity distributions of p(), π±, K± at different collision energies are presented. We also study two-particle angular correlations for stable charged particles. Results of simulations with PYTHIA, EPOS, SMASH, and UrQMD event generators are compared to available data. Connections of studied quantities with physics mechanisms in MC generators are discussed. We suggest a tuned set of parameters to address observed discrepancies between data and PYTHIA. [ABSTRACT FROM AUTHOR]

In this paper, we present two machine learning algorithms to identify D mesons produced in a colour singlet state from radiative W boson decays at the LHC. The combined network algorithm is able to identify D mesons via its hadronic decays with an efficiency of 47% while suppressing a background of quark and gluon jets by a factor of 100. Using the developed algorithm, we perform a prospective study for the measurement of B (W → D s γ) . [ABSTRACT FROM AUTHOR]

It has been known for many years that jet cross sections at hadron colliders exhibit double-logarithmic corrections starting at four-loop order, arising from two soft Glauber-gluon interactions between the two colliding partons. The resummation of these "super-leading logarithms" has been achieved only recently by means of a renormalization-group treatment in soft-collinear effective theory. We generalize this result and, within the same framework and for quark-initiated processes, resum the double logarithms arising in the presence of an arbitrary number of Glauber-gluon exchanges. For typical choices of parameters, the higher-order Glauber terms give rise to corrections which are expected to be numerically of the same magnitude as the super-leading logarithms. However, we find that the Glauber series for jet cross sections is dominated by the two-Glauber contribution, if the colliding partons are quarks or anti-quarks. [ABSTRACT FROM AUTHOR]

In this work, we provide a comprehensive set of differential cross-section distributions for photon + di-jet production in proton-proton collisions with next-to-next-to-leading order precision in massless QCD. The event selection corresponds to recent measurements by the ATLAS collaboration. We observe an improved description of data in comparison to lower-order calculations in the case of observables that are expected to be well described by perturbation theory. The results also show better agreement with data than parton-shower-matched and multi-jet-merged predictions generated for the ATLAS analysis using the Sherpa Monte Carlo. A particular highlight of our study is the use of exact five-point two-loop virtual amplitudes. This is the first calculation of a complete two-to-three hadron-collider process at next-to-next-to-leading order in QCD that does not rely on the leading-colour approximation at two loops. We demonstrate, nevertheless, that the sub-leading-colour effects present in the infraredand ultraviolet-finite double-virtual contributions are negligible in view of the remaining scale uncertainties. [ABSTRACT FROM AUTHOR]

A measurement of novel event shapes quantifying the isotropy of collider events is performed in 140 fb−1 of proton-proton collisions with s = 13 TeV centre-of-mass energy recorded with the ATLAS detector at CERN's Large Hadron Collider. These event shapes are defined as the Wasserstein distance between collider events and isotropic reference geometries. This distance is evaluated by solving optimal transport problems, using the 'Energy-Mover's Distance'. Isotropic references with cylindrical and circular symmetries are studied, to probe the symmetries of interest at hadron colliders. The novel event-shape observables defined in this way are infrared- and collinear-safe, have improved dynamic range and have greater sensitivity to isotropic radiation patterns than other event shapes. The measured event-shape variables are corrected for detector effects, and presented in inclusive bins of jet multiplicity and the scalar sum of the two leading jets' transverse momenta. The measured distributions are provided as inputs to future Monte Carlo tuning campaigns and other studies probing fundamental properties of QCD and the production of hadronic final states up to the TeV-scale. [ABSTRACT FROM AUTHOR]

Featured Application: This work describes a detailed study of two possible options for the magnetic system of a Future Circular hadron-hadron Collider detector. The conceptual design study of a Future Circular hadron-hadron Collider (FCC-hh) to be constructed at CERN with a center-of-mass energy of the order of 100 TeV requires superconducting magnetic systems with a central magnetic flux density of an order of 4 T for the experimental detectors. The developed concept of the FCC-hh detector involves the use of an iron-free magnetic system consisting of three superconducting solenoids. A superconducting magnet with a minimal steel yoke is proposed as an alternative to the baseline iron-free design. In this study, both magnetic system options for the FCC-hh detector are modeled with the same electrical parameters using Cobham's program TOSCA. All the main characteristics of both designs are compared and discussed. [ABSTRACT FROM AUTHOR]

In a framework of simplified model, we perform a simulated search for the singlet vector-like bottom quark B decaying into tW with t hadronic decay and W leptonic decay at the 14 TeV high-luminosity LHC (HL-LHC), 27 TeV high energy LHC (HE-LHC) and 100 TeV Future Circular Hadron Collider (FCC-hh). In this work, we focus on the case that the B only couples with the third generation quarks of the Standard Model. We make a detailed detector simulations of the signal and backgrounds and obtain the 2 σ exclusion limit and 5 σ discovery prospects. Our results show that the upcoming HL-LHC can exclude (discover) the m B to 2100 (1900) GeV for a typical coupling strength g ∗ = 0.2 . For the HE-LHC (FCC-hh), this exclusion capability on the B quark mass can be expanded to more than 3000 (5000) GeV. [ABSTRACT FROM AUTHOR]

Simulations play a key role for inference in collider physics. We explore various approaches for enhancing the precision of simulations using machine learning, including interventions at the end of the simulation chain (reweighting), at the beginning of the simulation chain (pre-processing), and connections between the end and beginning (latent space refinement). To clearly illustrate our approaches, we use W + jets matrix element surrogate simulations based on normalizing flows as a prototypical example. First, weights in the data space are derived using machine learning classifiers. Then, we pull back the data-space weights to the latent space to produce unweighted examples and employ the Latent Space Refinement (Laser) protocol using Hamiltonian Monte Carlo. An alternative approach is an augmented normalizing flow, which allows for different dimensions in the latent and target spaces. These methods are studied for various pre-processing strategies, including a new and general method for massive particles at hadron colliders that is a tweak on the widely-used RamboOnDiet mapping. We find that modified simulations can achieve sub-percent precision across a wide range of phase space. [ABSTRACT FROM AUTHOR]

Bremsstrahlung spectra will be strongly distorted due to small lateral beam sizes at future colliders. That in turn will have large consequences for the electron and positron beam lifetimes as well as for the luminosity measurements in the case of electron-hadron colliders. We discuss in detail such consequences for the future circular collider and large hadron electron collider cases. [ABSTRACT FROM AUTHOR]

We discuss the discovery potential of a promising signals, 3 × μ + μ - at a μ + μ - collider and μ + μ + μ + μ + μ - μ - at a μ + μ + collider, that are obtained via production of Z ′ and a new scalar boson ϕ in a spontaneously broken local U (1) L μ - L τ model. We consider the Z ′ associated production from the process μ + μ - → ϕ Z ′ in addition to a muonphilic Z ′ fusion process μ + μ ± → ϕ μ + μ ± . The scalar boson is associated with U (1) L μ - L τ symmetry breaking and dominantly decays into Z ′ Z ′ mode. We carry out numerical simulation analysis for signal and background processes to estimate a discovery significance for different benchmark points. It is shown that our signal can be observed with integrated luminosity less than O (100) fb - 1 for both μ + μ - and μ + μ + colliders with more than 5- σ significance. [ABSTRACT FROM AUTHOR]

Quantum entanglement of weak interaction gauge bosons produced at colliders can be explored by computing the corresponding polarization density matrix. To this end, we consider the Higgs boson decays H → W W ∗ and H → Z Z ∗ , in which W ∗ and Z ∗ are off-shell states, and the WW, WZ and ZZ di-boson production in proton collisions. The polarization density matrix of the di-boson state is determined by the amplitude of the production process and can be experimentally reconstructed from the angular distribution of the momenta of the final states into which the gauge bosons decay. We show that a suitable instance of the Bell inequality is violated in H → Z Z ∗ to a degree that can be tested at the LHC with future data. The same Bell inequality is violated in the production of WW and ZZ boson pairs for invariant masses above 900 GeV and scattering angles close to π / 2 in the center of mass frame. LHC data in this case are not sufficient to establish the violation of the Bell inequality. We also analyze the prospects for detecting Bell inequality violations in di-boson final states at future e + e - and muon colliders. A further observable that provides a lower bound on the amount of polarization entanglement in the di-boson system is computed for each of the examined processes. The analytic expressions for the polarization density matrices are presented in full in an Appendix. We also provide the unitary matrices required in the optimization procedure necessary in testing the Bell inequalities. [ABSTRACT FROM AUTHOR]

We present a comprehensive study on how to distinguish the properties of heavy dijet resonances at hadron colliders. A variety of spins, chiral couplings, charges, and QCD color representations are considered. Distinguishing the different color representations is particularly difficult at hadron colliders. To determine the QCD color structure, we consider a third jet radiated in a resonant dijet event. We show that the relative rates of three-jet versus two-jet processes are sensitive to the color representation of the resonance. We also show analytically that the antennae radiation pattern of soft radiation depends on the color structure of dijet events and develops an observable that is sensitive to the antennae patterns. Finally, we exploit a Convolutional Neural Network with Machine Learning techniques to differentiate the radiation patterns from different colored resonances and find encouraging results to discriminate them. We demonstrate our results numerically at a 14 TeV LHC, and the methodology presented here should be applicable to other future hadron colliders. [ABSTRACT FROM AUTHOR]

Lepton flavor violation is one of the cleanest probes of physics beyond the standard model. In this work, we explore the sensitivity of the process e+e− → τμ to new physics above the TeV scale at the proposed circular electron-positron colliders FCC-ee and CEPC. We compute the e+e− → τμ cross-section in the Standard Model Effective Field Theory and assess the relevant backgrounds. We compare our sensitivity projections to existing and expected constraints from tau decays and Z decays and find that the future electron-positron colliders provide competitive probes of new physics. We highlight the complementarity of searches for resonant e+e−→ Z → τμ production on the Z pole and searches for non-resonant e+e−→ τμ at higher center-of-mass energies. [ABSTRACT FROM AUTHOR]

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A search for diphoton resonances in the mass range between 10 and 70 GeV with the ATLAS experiment at the Large Hadron Collider (LHC) is presented. The analysis is based on pp collision data corresponding to an integrated luminosity of 138 fb−1 at a centre-of-mass energy of 13 TeV recorded from 2015 to 2018. Previous searches for diphoton resonances at the LHC have explored masses down to 65 GeV, finding no evidence of new particles. This search exploits the particular kinematics of events with pairs of closely spaced photons reconstructed in the detector, allowing examination of invariant masses down to 10 GeV. The presented strategy covers a region previously unexplored at hadron colliders because of the experimental challenges of recording low-energy photons and estimating the backgrounds. No significant excess is observed and the reported limits provide the strongest bound on promptly decaying axion-like particles coupling to gluons and photons for masses between 10 and 70 GeV. [ABSTRACT FROM AUTHOR]

In this article, we consider the transverse momentum (qT) distribution of W and Z bosons produced in hadronic collisions. We combine the qT resummation for QED and QCD radiation including the QED soft emissions from the W boson in the final state. In particular, we perform the resummation of enhanced logarithmic contributions due to soft and collinear emissions at next-to-leading accuracy in QED, leading-order accuracy for mixed QED-QCD and next-to-next-to-leading accuracy in QCD. In the small-qT region we consistently include in our results the next-to-next-to-leading order (i.e. two loops) QCD corrections and the next-to-leading order (i.e. one loop) electroweak corrections. The matching with the fixed-order calculation at large qT has been performed at next-to-leading order in QCD (i.e. at O α S 2 ) and at leading order in QED. We show numerical results for W and Z production at the Tevatron and the LHC. Finally, we consider the effect of combined QCD and QED resummation for the ratio of W and Z qT distributions, and we study the impact of the QED corrections providing an estimate of the corresponding perturbative uncertainties. [ABSTRACT FROM AUTHOR]

We have calculated the complete two-loop QCD amplitudes for hadronic tW production by combining analytical and numerical techniques. The amplitudes have been first reduced to master integrals of eight planar and seven non-planar families, which can contain at most four massive propagators. Then a rational transformation of the master integrals is found to obtain a good basis so that the dimensional parameter decouples from the kinematic variables in the denominators of reduction coefficients. The master integrals are computed by solving their differential equations numerically. We find that the finite part of the two-loop squared amplitude is stable in the bulk of the phase space. After phase space integration and convolution with the parton distributions, it increases the LO cross section at the 13 TeV LHC by about 3%. [ABSTRACT FROM AUTHOR]

In this paper, we study the potential of future colliders to explore the parameter space of heavy neutral leptons (HNLs) through the dipole portal. We consider hadron colliders such as the LHC in the high luminosity phase and FCC-hh, and lepton colliders, such as FCC-ee. We consider various signatures for the HNLs, including the missing energy signature and displaced decays, and discuss the complementarity between the hadron and lepton colliders. We propose new selection rules which may significantly reduce the background events in FCC-ee. In particular, we find that thanks to a much clearer environment, FCC-ee may search for the HNLs with masses up to ≃ 30 GeV and proper lifetimes cτN ≳ 1 cm, which is well beyond the reach of the experiments to be launched in the next decade. [ABSTRACT FROM AUTHOR]

Parton labeling methods are widely used when reconstructing collider events with top quarks or other massive particles. State-of-the-art techniques are based on machine learning and require training data with events that have been matched using simulations with truth information. In nature, there is no unique matching between partons and final state objects due to the properties of the strong force and due to acceptance effects. We propose a new approach to parton labeling that circumvents these challenges by recycling regression models. The final state objects that are most relevant for a regression model to predict the properties of a particular top quark are assigned to said parent particle without having any parton-matched training data. This approach is demonstrated using simulated events with top quarks and outperforms the widely-used χ 2 method. [ABSTRACT FROM AUTHOR]

Central exclusive diffractive production (CEDP) of proton–anti-proton pairs is calculated in the Regge-eikonal approach taking into account continuum and possible f 0 (2100) resonance. We use the simple model with the "scalar" proton. Data from ISR and STAR are analysed and compared with theoretical descriptions. Some predictions for the LHC at 13 TeV are also presented. We briefly discuss possible nuances, problems and prospects for investigations of this process at present and future hadron colliders. [ABSTRACT FROM AUTHOR]

We readdress the issue of strong CP violation both in the Standard Model (SM) and in the Minimal Left–Right (LR) Symmetric Model and try to clear the confusion that seems to still pervade the field. We argue that the smallness of strong CP violation, while harmless and basically decoupled from the rest of the physics in the SM, in the context of LR symmetry provides a blessing by helping to narrow down the parameter space of the theory and connecting apparently the uncorrelated physical quantities. In particular, in the context of left–right symmetry being parity, it either points to the suppression of leptonic CP violation noticed before, or leads to relatively light right-handed neutrinos, potentially accessible at the next hadron collider. The latter, more natural in view of complex quark Yukawa couplings, goes hand in hand with the smallness of lepton flavor violation and enhances the possibility of observing neutrinoless double-beta decay. [ABSTRACT FROM AUTHOR]

Diboson production processes provide good targets for precision measurements at present and future hadron colliders. We consider Vh production, focusing on the h → b b ¯ decay channel, whose sizeable cross section makes it accessible at the LHC. We perform an improved analysis by combining the 0-, 1- and 2-lepton channels with a scale-invariant b-tagging algorithm that allows us to exploit events with either a boosted Higgs via mass-drop tagging or resolved b-jets. This strategy gives sensitivity to 4 dimension-6 SMEFT operators that modify the W and Z couplings to quarks and is competitive with the bounds obtained from global fits. The benefit of the h → b b ¯ decay channel is the fact that it is the only Vh channel accessible at the LHC Run 3 and HL-LHC, while at FCC-hh it is competitive with the effectively background-free h → γγ channel assuming ≲ 5% systematic uncertainty. Combining the boosted and resolved categories yields a 17% improvement on the most strongly bounded Wilson coefficient at the LHC Run 3 with respect to the boosted category alone (and a 7% improvement at FCC-hh). We also show that, at FCC-hh, a binning in the rapidity of the Vh system can significantly reduce correlations between some EFT operators. The bounds we obtain translate to a lower bound on the new physics scale of 5, 8, and 20 TeV at the LHC Run 3, HL-LHC, and FCC-hh respectively, assuming new-physics couplings of order unity. Finally, we assess the impact of the Vh production channel on anomalous triple gauge coupling measurements, comparing with their determination at lepton colliders. [ABSTRACT FROM AUTHOR]

The well understood structure of U pmns matrix mandates a Cabibbo mixing matrix in the first two generations of the charged lepton sector if we assume Tri-bimaximal mixing in the neutrino sector. This ansatz, called Tri-bimaximal-Cabibbo mixing, is ruled out immediately by the experiments searching for charged lepton flavour violating currents. In this article, we aim to show that the resurrection of the theoretically well motivated Tri-bimaximal mixing scenario comes naturally within Minimal Flavour Violation hypothesis in the lepton sector. We analyse the flavour violating currents μ → e e e , μ T i → e T i , μ → e γ , π 0 → e + μ - and K L → μ + e - in this scenario and show that the New Physics that generates mixing among the charged lepton could lie within the reach of hadron colliders. In the minimal field content scenario, though the most stringent constrain on New Physics is ≳ O (10 TeV) for maximal coupling, considering more natural couplings relaxes it to ≳ O (4 TeV). On the other hand, New Physics with the extended field content is even more strongly constrained to ≳ O (75 TeV) for maximal coupling, while it gets relaxed to ≳ O (31 TeV) for natural scenario. [ABSTRACT FROM AUTHOR]