HEP Phenomenology·hep-ph
26 papers—18 primary·8 cross-listed·reconstructed*
This paper discusses a statistical anomaly-detection method for model-independent searches for new physics in collision events produced at the Large Hadron Collider (LHC). The method requires calculations of -scores for a large number of Lorenz-invariant variables to identify events that deviate from those expected for the Standard Model (SM).
Jin-Bao Wang🇨🇳 · Gang Li🇨🇳 · Cheng-Rong Deng🇨🇳 · Chun-Sheng An🇨🇳 · Ju-Jun Xie🇨🇳
Spectrum of the low-lying resonances with negative parity, which are assumed to be dominated by pentaquark components, is investigated using the chiral constituent quark model. Energies of the resonances are obtained by considering the hyperfine interaction between quarks by exchanging Goldstone boson. Possible configurations with spin-parity , and are taken into account. Numerical results show that the lowest resonances with negative parity may lie at MeV. In addition, the transitions of the resonance to a pseudoscalar meson and a ground baryon state are also investigated within the chiral Lagrangian approach. We expect that these resonances could be observed in the channel by future experiments.
Jin-Li Zhang🇨🇳 · Guang-Zhen Kang🇨🇳 · Jia-Lun Ping🇨🇳
Pion generalised parton distributions are calculated within the framework of the Nambu--Jona-Lasinio model using different regularization schemes, including the proper time regularization scheme, the three dimensional momentum cutoff scheme, the four dimensional momentum cutoff scheme, and the Pauli-Villars regularization scheme. Furthermore, we check the theoretical constraints of pion generalised parton distributions required by the symmetries of quantum chromodynamics in different regularization schemes. The diagrams of pion parton distribution functions are plotted, in addition, we evaluate the Mellin moments of generalised parton distributions, which related to the electromagnetic and gravitational form factors of pion. Pion generalised parton distributions are continuous but not differential at , when considering the effect of D-term, generalised parton distributions become not continuous at in all the four regularization schemes. Generalised parton distributions in impact parameter space are considered, the width distribution of quark in the pion and the mean-squared are calculated. The light-front transverse-spin distributions are studied, when quark polarized in the light-front-transverse direction, the transverse-spin density is no longer symmetric around , the peaks shift to , we compare the average transverse shift and in different regularization schemes. The light-cone energy radius and the light-cone charge radius are also evaluated, we find that in the proper time regularization scheme the values of these quantities are the largest, in the three dimensional momentum cutoff scheme they are the smallest.
In this talk we discuss recent computations of the top quark mass dependence of QCD amplitudes describing Higgs boson production in gluon fusion. We compute terms in the expansion for a large top quark mass, which reduces the Feynman diagrams to products of massless integrals and massive tadpole integrals which contain the top mass dependence. In particular we discuss the real and virtual corrections to double Higgs production at NNLO, and the virtual corrections to single Higgs production at N3LO.
M. Mühlleitner🇩🇪 · J. Müller🇩🇪 · S.L. Williamson🇩🇪 · J. Wittbrodt🇸🇪
We present the CP-violating Next-to-2-Higgs-Doublet Model (CN2HDM) which is based on the extension of the CP-violating 2-Higgs-Doublet-Model (C2HDM) by a complex singlet field that obeys a discrete symmetry. The model thus features not only CP violation required for successful electroweak baryogenesis but also a Dark Matter (DM) candidate. The model has an extended Higgs sector with four CP-mixing visible neutral Higgs bosons, a DM candidate and a pair of oppositely charged Higgs bosons. The possibility of singlet and CP-odd admixtures to the observed Higgs boson in addition to the large number of visible scalar particles leads to an interesting Higgs phenomenology. We find that the model can easily provide 100\% of the DM relic density and investigate interesting LHC and DM observables within the model. We provide all the tools necessary to study the CN2HDM in detail and point out future research directions for this interesting benchmark model that can address some of the most pressing open questions of the Standard Model.
Francisco J. de Anda🇲🇽 · Omar Medina🇪🇸 · José W. F. Valle🇪🇸 · Carlos A. Vaquera-Araujo🇲🇽
The use of extra space-time dimensions provides a promising approach to the flavour problem. The chosen compactification of a 6-dimensional orbifold implies a remnant family symmetry . This makes interesting predictions for quark and lepton masses, for neutrino oscillations and neutrinoless double beta decay, providing also a very good global description of all flavour observables. Due to an auxiliary symmetry, we implement a scotogenic Majorana neutrino mass generation mechanism with a viable WIMP dark matter candidate.
C. Giunti🇮🇹 · Y.F. Li🇨🇳 · C.A. Ternes🇮🇹 · Z. Xin🇨🇳
We study the status of the reactor antineutrino anomaly in light of recent reactor flux models obtained with the conversion and summation methods. We present a new improved calculation of the IBD yields of the standard Huber-Mueller (HM) model and those of the new models. We show that the reactor rates and the fuel evolution data are consistent with the predictions of the Kurchatov Institute (KI) conversion model and with those of the Estienne-Fallot (EF) summation model, leading to a plausible robust demise of the reactor antineutrino anomaly. We show that the results of several goodness of fit tests favor the KI and EF models over other models that we considered. We also discuss the implications of the new reactor flux models for short-baseline neutrino oscillations due to active-sterile oscillations. We show that reactor data give upper bounds on active-sterile neutrino mixing that are not very different for the reactor flux models under consideration and are in tension with the large mixing required by the Gallium anomaly that has been refreshed by the recent results of the BEST experiment.
M.D. Adzhymambetov🇺🇦 · S.V. Akkelin🇺🇦 · Yu.M. Sinyukov🇺🇦
Two-boson momentum correlations at fixed particle number constraint are studied in a simple analytically solvable model of a thermal expanding system. We show that the increase of expansion rate, as well as increase of particle multiplicity, enhances the ground-state contribution to particle momentum spectra and leads to suppression of the Bose-Einstein momentum correlations. The relations of these findings to the multiplicity-dependent measurements of the Bose-Einstein momentum correlations in high-multiplicity collision events at the LHC are discussed.
John Ellis🇬🇧 · Jason L. Evans🇨🇳 · Natsumi Nagata🇯🇵 · Dimitri V. Nanopoulos🇺🇸 · Keith A. Olive🇺🇸
We consider proton decay and in flipped SU(5) GUT models. We first study scenarios in which the soft supersymmetry-breaking parameters are constrained to be universal at some high scale above the standard GUT scale where the QCD and electroweak SU(2) couplings unify. In this case the proton lifetime is typically ~yrs, too long to be detected in the foreseeable future, and the supersymmetric contribution to is too small to contribute significantly to resolving the discrepancy between the experimental measurement and data-driven calculations within the Standard Model. However, we identify a region of the constrained flipped SU(5) parameter space with large couplings between the 10- and 5-dimensional GUT Higgs representations where decay may be detectable in the Hyper-Kamiokande experiment now under construction, though the contribution to is still small. A substantial contribution to is possible, however, if the universality constraints on the soft supersymmetry-breaking masses are relaxed. We find a `quadrifecta' region where observable proton decay co-exists with a (partial) supersymmetric resolution of the discrepancy and acceptable values of and the relic LSP density.
Over the last decade the gradient flow formalism became an important tool for lattice simulations of Quantum Chromodynamics. It offers remarkable renormalization properties which pave the way for cross-fertilization between perturbative and lattice calculations. In this contribution we discuss the perturbative approach. As first application we compute vacuum expectation values of flowed operators which could help to extract parameters like the strong coupling constant from lattice simulations. Afterwards, we apply the flowed operator product expansion to the time-ordered product of two currents which could be employed for an alternative first-principle evaluation of vacuum polarization functions on the lattice.
We propose a new approach that allows for the separate numerical calculation of the real and imaginary parts of finite loop integrals. We find that at one-loop the real part is given by the Loop-Tree Duality integral supplemented with suitable counterterms and the imaginary part is a sum of two-body phase space integrals, constituting a locally finite representation of the generalised optical theorem. These expressions are integrals in momentum space, whose integrands were specially designed to feature local cancellations of threshold singularities. Such a representation is well suited for Monte Carlo integration and avoids the drawbacks of a numerical contour deformation around remaining singularities. Our method is directly applicable to a range integrals with certain geometric properties but not yet fully generalised for arbitrary one-loop integrals. We demonstrate the computational performance with examples of one-loop integrals with various kinematic configurations, which gives promising prospects for an extension to multi-loop integrals.
Saumyen Kundu🇮🇳 · Atanu Guha🇮🇳 · Prasanta Kumar Das🇮🇳 · P. S. Bhupal Dev🇺🇸
We consider the possibility that dark matter (DM) only interacts with the Standard Model leptons, but not quarks at tree level, and analyze the future lepton collider prospects of such leptophilic DM in the monophoton and mono- (both leptonic and hadronic) channels. Adopting a model-independent effective field theory framework, we consider all possible dimension-six operators of scalar-pseudoscalar (SP), vector-axial vector (VA), and tensor-axial tensor (TAT) types for a fermionic DM and derive the collider sensitivities on the effective cutoff scale as a function of the DM mass. As a concrete example, we take the beam configurations of the International Linear Collider with TeV and ab integrated luminosity, including the effect of beam polarization, and show that it can probe leptophilic DM at level up to values of , , and TeV for the SP-, VA- and TAT-type operators, respectively. This is largely complementary to the direct and indirect searches for leptophilic DM and can potentially provide the best-ever sensitivity in the low-mass DM regime.
Luca Buonocore🇨🇭 · Massimiliano Grazzini🇨🇭 · Jürg Haag🇨🇭 · Luca Rottoli🇨🇭
We consider the associated production of a vector or Higgs boson with a jet in hadronic collisions. When the transverse momentum of the boson-jet system is much smaller than its invariant mass , the QCD perturbative expansion is affected by large logarithmic terms that must be resummed to all orders. We discuss the all-order resummation structure of the logarithmically enhanced contributions up to next-to-leading logarithmic accuracy. Resummation is performed at the differential level with respect to the kinematical variables of the boson-jet system. Soft-parton radiation produces azimuthal correlations that are fully accounted for in our framework. We present explicit analytical results for the resummation coefficients up to next-to-leading order and next-to-leading logarithmic accuracy, that include the exact dependence on the jet radius.
Sally Dawson🇺🇸 · Samuel Homiller🇺🇸 · Matthew Sullivan🇺🇸
The use of the SMEFT Lagrangian to quantify possible Beyond the Standard Model (BSM) effects is standard in LHC and future collider studies. One of the usual assumptions is to truncate the expansion with the dimension- operators. The numerical impact of the next terms in the series, the dimension- operators, is unknown in general. We consider a specific BSM model containing a charge- heavy vector-like quark and compute the operators generated at dimension-. The numerical effects of these operators are studied for the process, where they contribute at tree level and we find effects at the level for allowed values of the parameters.
In this contribution we consider the recent computation of the gauge coupling -function at four loops and the Yukawa matrix -function at three loops in the most general, renormalizable and four-dimensional quantum field theory. Furthermore, we discuss ambiguities and divergences arising in Yukawa matrix -functions.
Gauthier Durieux🇨🇭 · Matthew McCullough🇨🇭 · Ennio Salvioni🇨🇭
We investigate radiatively stable classes of pseudo-Nambu-Goldstone boson (pNGB) potentials for approximate spontaneously broken . Using both the one-loop effective action and symmetry, it is shown that a Gegenbauer polynomial potential is radiatively stable, being effectively an `eigenfunction' from a radiative perspective. In Gegenbauer pNGB models, one naturally and automatically obtains , where is the order of the Gegenbauer polynomial. For a Gegenbauer Higgs boson, this breaks the usual correlation between Higgs coupling corrections and `' tuning. Based on this, we argue that to conclusively determine whether or not the Higgs is a composite pNGB in scenarios with up to fine-tuning will require going beyond both the Higgs coupling precision and heavy resonance mass reach of the High-Luminosity LHC.
Katherine Fraser🇺🇸 · Samuel Homiller🇺🇸 · Rashmish K. Mishra🇺🇸 · Bryan Ostdiek🇺🇸 · Matthew D. Schwartz🇺🇸
Anomaly detection relies on designing a score to determine whether a particular event is uncharacteristic of a given background distribution. One way to define a score is to use autoencoders, which rely on the ability to reconstruct certain types of data (background) but not others (signals). In this paper, we study some challenges associated with variational autoencoders, such as the dependence on hyperparameters and the metric used, in the context of anomalous signal (top and ) jets in a QCD background. We find that the hyperparameter choices strongly affect the network performance and that the optimal parameters for one signal are non-optimal for another. In exploring the networks, we uncover a connection between the latent space of a variational autoencoder trained using mean-squared-error and the optimal transport distances within the dataset. We then show that optimal transport distances to representative events in the background dataset can be used directly for anomaly detection, with performance comparable to the autoencoders. Whether using autoencoders or optimal transport distances for anomaly detection, we find that the choices that best represent the background are not necessarily best for signal identification. These challenges with unsupervised anomaly detection bolster the case for additional exploration of semi-supervised or alternative approaches.
X. Chen🇨🇭 · A. Huss🇨🇭 · S. P. Jones🇬🇧 · M. Kerner🇨🇭 · J.-N. Lang🇨🇭 · J. M. Lindert🇬🇧 · H. Zhang🇨🇭
We present calculations of Higgs boson production via gluon-gluon fusion in association with one or two additional jets at next-to-leading order in QCD. The calculation of H+jet is exact in the treatment of the top-quark mass, whereas for the H+2 jets calculation the two-loop virtual amplitudes are approximated via a reweighting with leading-order mass effects, while keeping all top-quark mass effects in the real radiation contributions. For H+jet production, this study extends a previous calculation, revealing an error in the previous results. For total and differential cross sections, we present new results and compare the QCD corrections with the infinite top-mass limit, for which we find a strikingly good agreement if all amplitudes are rescaled by the leading-order mass dependence.
Latham Boyle🇨🇦 · Neil Turok🇨🇦
The standard model is a remarkably consistent and complete quantum field theory but its coupling to gravity and the Higgs field remain problematic, as reflected in the cosmological constant problem, the Weyl anomaly, and the hierarchy puzzle. We point out that 36 conformally-coupled dimension-zero scalar fields can simultaneously cancel the vacuum energy and both terms in the Weyl anomaly, if the Higgs field is emergent. The cancellation is highly non-trivial: given the standard model gauge group , it requires precisely Weyl fermions, {\it i.e.}, three generations of standard model fermions, including right-handed neutrinos. Due to a large additional gauge symmetry, the new scalars contribute no new local degrees of freedom or particle states. Their only physical state is their vacuum state, in which they possess a scale invariant power spectrum extending to long wavelengths. This suggests a new explanation for the primordial scalar perturbations in cosmology, not requiring inflation. We also discuss how the Higgs field might emerge as a composite object.
The large-momentum effective theory (LaMET) framework has been widely used to determine the Bjorken- dependence of parton distribution functions (PDFs) in lattice-QCD hadron-structure calculations. In this proceeding, I highlighted selected recent lattice-QCD results on parton distributions from MSULat group. We use clover valence fermions on ensembles generated by MILC Collaboration with lattice spacing , 0.09, and 0.12 fm, with , and with pion masses including 135, 220 and 310 MeV and flavors of highly improved staggered dynamical quarks. Results include the continuum-physical isovector nucleon PDF, a first study of the strange and charm PDFs and the pion and kaon valence-quark PDFs. We also reported results on the and dependence of nucleon isovector unpolarized and helicity GPDs calculated directly at physical pion mass; we also make a comparison of the GPDs with the traditional moment methods from other lattice calculations.
Primordial Black Holes (PBH) can form in the early universe and might comprise a significant fraction of the dark matter. Interestingly, they are accompanied by the generation of Gravitational Wave (GW) signals and they could contribute to the merger events currently observed by the LIGO/Virgo Collaboration (LVC). In this thesis, we study the PBH scenario, addressing various properties at the formation epoch and the computation of abundance beyond the Gaussian paradigm, while also developing the theoretical description of PBH evolution through accretion and mergers, with particular focus on modelling their GW signatures. In a second part, we compare the primordial scenario with current GW data, seizing the possible contribution of PBH binaries to LVC signals and forecasting the potential of future GW detectors, such as Einstein Telescope and LISA, to detect mergers of primordial binaries and the stochastic GW background induced at second order by the PBH formation mechanism.
This thesis deals with the study of properties and interactions of light mesons. Specifically, we focus on hadronic decay and scattering processes, which are dominated by effects of the strong interaction in the low-energy regime. A peculiarity of the strong interaction is that perturbative expansions fail at hadronic energy scales. Thus, genuine nonperturbative tools are essential to obtain first-principles predictions. Here we use Lattice Field Theory, and Effective Field Theories. The mathematical formulation of Quantum Chromodynamics (QCD) and the methods to resolve its dynamics will be addressed in Chapter 1. The research of this dissertation is divided in two parts. Chapter 2 describes our study of the 't Hooft limit of QCD using lattice simulations, while in Chapter 3 we consider processes that involve multiparticle states. The 't Hooft limit provides a simplification of nonabelian gauge theories that leads to nonperturbative predictions. We will analyze the scaling with the number of colours of various observables, such as meson masses, decay constants and weak matrix elements. A question we address is the origin of the long-standing puzzle of the rule, that is, the large hierarchy in the isospin amplitudes of the weak decay. Regarding multiparticle processes, we will discuss generalizations of the Lüscher formalism to explore three-particle processes from lattice simulations. The focus will be on our contributions, such as our implementation of the finite-volume formalism that includes higher partial waves, and the first application of the formalism to a full lattice QCD spectrum. We will also comment on the extension of the approach to generic three-pion systems. A summary in Spanish will be given in Chapter 4. The final part of the thesis (Part II) includes the peer-reviewed publications in their original published form.
Siddharth Mishra-Sharma🇺🇸 · Kyle Cranmer🇺🇸
The nature of the Fermi gamma-ray Galactic Center Excess (GCE) has remained a persistent mystery for over a decade. Although the excess is broadly compatible with emission expected due to dark matter annihilation, an explanation in terms of a population of unresolved astrophysical point sources e.g., millisecond pulsars, remains viable. The effort to uncover the origin of the GCE is hampered in particular by an incomplete understanding of diffuse emission of Galactic origin. This can lead to spurious features that make it difficult to robustly differentiate smooth emission, as expected for a dark matter origin, from more "clumpy" emission expected for a population of relatively bright, unresolved point sources. We use recent advancements in the field of simulation-based inference, in particular density estimation techniques using normalizing flows, in order to characterize the contribution of modeled components, including unresolved point source populations, to the GCE. Compared to traditional techniques based on the statistical distribution of photon counts, our machine learning-based method is able to utilize more of the information contained in a given model of the Galactic Center emission, and in particular can perform posterior parameter estimation while accounting for pixel-to-pixel spatial correlations in the gamma-ray map. This makes the method demonstrably more resilient to certain forms of model misspecification. On application to Fermi data, the method generically attributes a smaller fraction of the GCE flux to unresolved point sources when compared to traditional approaches. We nevertheless infer such a contribution to make up a non-negligible fraction of the GCE across all analysis variations considered, with at least of the excess attributed to unresolved point sources in our baseline analysis.
Carlos Bravo-Prieto🇪🇸 · Julien Baglio🇨🇭 · Marco Cè🇨🇭 · Anthony Francis🇨🇭 · Dorota M. Grabowska🇨🇭 · Stefano Carrazza🇮🇹
We propose and assess an alternative quantum generator architecture in the context of generative adversarial learning for Monte Carlo event generation, used to simulate particle physics processes at the Large Hadron Collider (LHC). We validate this methodology by implementing the quantum network on artificial data generated from known underlying distributions. The network is then applied to Monte Carlo-generated datasets of specific LHC scattering processes. The new quantum generator architecture leads to a generalization of the state-of-the-art implementations, achieving smaller Kullback-Leibler divergences even with shallow-depth networks. Moreover, the quantum generator successfully learns the underlying distribution functions even if trained with small training sample sets; this is particularly interesting for data augmentation applications. We deploy this novel methodology on two different quantum hardware architectures, trapped-ion and superconducting technologies, to test its hardware-independent viability.
Tetyana Pitik🇩🇰 · Irene Tamborra🇩🇰 · Charlotte R. Angus🇩🇰 · Katie Auchettl🇦🇺
The Zwicky Transient Facility (ZTF) follow-up campaign of alerts released by the IceCube Neutrino Observatory has led to the likely identification of the transient AT2019fdr as the source of the neutrino event IC200530A. AT2019fdr was initially suggested to be a tidal disruption event in a Narrow-Line Seyfert 1 galaxy. However, the combination of its spectral properties, color evolution, and feature-rich light curve suggests that AT2019fdr may be a Type IIn superluminous supernova. In the latter scenario, IC200530A may have been produced via inelastic proton-proton collisions between the relativistic protons accelerated at the forward shock and the cold protons of the circumstellar medium. Here, we investigate this possibility and find that at most muon neutrino and antineutrino events are expected to be detected by the IceCube Neutrino Observatory within days of discovery in the case of excellent discrimination of the atmospheric background. After correcting for the Eddington bias, which occurs when a single cosmic neutrino event is adopted to infer the neutrino emission at the source, we conclude that IC200530A may originate from the hydrogen-rich superluminous supernova AT2019fdr.
Maarten Van Damme🇧🇪 · Julius Mildenberger🇮🇹 · Fabian Grusdt🇩🇪 · Philipp Hauke🇮🇹 · Jad C. Halimeh🇮🇹
With recent progress in quantum simulations of lattice-gauge theories, it is becoming a pressing question how to reliably protect the gauge symmetry that defines such models. In a recent work [J. C. Halimeh \textit{et al.}, arXiv:2108.02203], an experimentally feasible gauge-protection scheme has been proposed that is based on the concept of a \textit{local pseudogenerator}, which is required to act identically to the full gauge-symmetry generator in the target gauge sector, but not necessarily outside of it. The scheme has been analytically and numerically shown to reliably stabilize lattice gauge theories in the presence of perturbative errors on finite-size analog quantum-simulation devices. In this work, through uniform matrix product state calculations, we demonstrate the efficacy of this scheme for nonperturbative errors in analog quantum simulators up to all accessible evolution times in the thermodynamic limit, where it is \textit{a priori} neither established nor expected that this scheme will succeed. Our results indicate the presence of an emergent gauge symmetry in an adjusted gauge theory even in the thermodynamic limit, which is beyond our analytic predictions. Additionally, we show through quantum circuit model calculations that gauge protection with local pseudogenerators also successfully suppresses gauge violations on finite quantum computers that discretize time through Trotterization. Our results firm up the robustness and feasibility of the local pseudogenerator as a viable tool for enforcing gauge invariance in modern quantum simulators and NISQ devices.
* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.