HEP Phenomenology·hep-ph
40 papers—32 primary·8 cross-listed·reconstructed*
G. Pancheri🇮🇹 · Y. N. Srivastava🇮🇹 · O. Shekhovtsova🇺🇦
We recall a resummation procedure in QED to extract the zero momentum mode in soft photon emission and present an ansatz about a possible mechanism for the forward peak characterizing elastic proton proton scattering.
Axion dark matter inevitably generates electromagnetic radiation in quantum Hall effect experiments that use strong magnetic fields. Although these emissions are very weak, we have shown using a QCD axion model that they influence the plateau-plateau transition at low temperatures (below mK) in a system with a large surface area (greater than ) of two-dimensional electrons. By analyzing previous experiments that show saturation of the transition width as temperature and microwave frequency change, we provide evidence for the presence of axions. Notably, in most experiments without axion effects, the saturation frequency is less than GHz at temperatures of mK or higher and for system sizes of or smaller. Additionally, the frequency decreases with decreasing temperature or increasing system size. However, there are experiments that show a saturation frequency GHz despite a low temperature of 35 mK and a large surface area of for the Hall bar. This identical frequency of approximately GHz has also been observed in different plateau transitions and in Hall bars of varying sizes. These unexpected results are caused by axion microwaves. The saturation frequency of GHz implies an axion mass of eV. By comparing the axion effect with thermal effect on the width , we have shown the dominance of the axion effect over thermal effect at low temperature less than mK. The dominance of the axion effect is attributed to significant absorption of axion energy, which is proportional to the square of the number of electrons involved.
Jinglong Zhu🇨🇳 · Hiroyuki Umeeda🇨🇳
In this work, nontrivial analytic structure of the quark propagator is discussed for -meson inclusive decays. Attributed to invalidity of the standard Källén-Lehman spectral representation, complex conjugate poles alter the evaluation of decay rates, which lead to violation of quark-hadron duality. As phenomenological observables, widths in decay as well as the lifetime of the meson are discussed. In the presence of the mentioned nonanalytical contributions, the possibility for resolving the puzzle is addressed. It is demonstrated that there exists a parameter region, which explains and -meson lifetime simultaneously within 1 via the complex conjugate poles from a charm quark.
U. Özdem🇹🇷
The magnetic moments of the mesons provide significant insights into their inner structure and geometric shape. Furthermore, a comprehensive understanding of the electromagnetic characteristics of mesons is essential for advancing our knowledge of confinement and heavy flavor effects. In light of this, we proceed to extract the magnetic moments of the ground-state vector and axial-vector mesons through the medium of the QCD light-cone sum rules. The magnetic moments of the axial-vector and vector mesons are found to be , and , respectively. A comparison of our results for the vector meson with other theoretical predictions has revealed discrepancies between the various predictions, which could prove useful as a complementary tool for interpreting the vector meson. The current experimental data set is limited to a small number of observed states of beauty-charm mesons. However, theoretical studies can play a valuable role in elucidating their nature and guiding future experimental investigations.
Zbigniew Drogosz🇵🇱 · Wojciech Florkowski🇵🇱 · Natalia Łygan🇵🇱 · Radoslaw Ryblewski🇵🇱
A recently formulated extension of perfect spin hydrodynamics, which includes second-order corrections in the spin polarization tensor to the energy-momentum tensor and baryon current, is studied in the case of a one-dimensional boost-invariant expansion. The presence of second-order corrections introduces feedback from spin dynamics on the hydrodynamic background, constraining possible spin polarization configurations. However, as long as the magnitude of the spin polarization tensor remains small (below unity in natural units), the permitted spin dynamics differs very little from that found in the case without the second-order corrections.
Patrick Copinger🇬🇧 · James P. Edwards🇬🇧 · Anton Ilderton🇬🇧 · Karthik Rajeev🇬🇧
We revisit particle creation in strong fields, and backreaction on those fields, from an amplitudes perspective. We describe the strong field by an initial coherent state of photons which we explicitly evolve in time, thus going beyond the background field approximation, and then consider observables which quantify the effects of backreaction. We present expressions for the waveform, vacuum persistence probability, and number of produced photons at next-to-leading order, all of which are impacted by backreaction, along with the number and statistics of produced pairs. We find that converting between in-out (amplitude) and in-in (expectation value) expressions requires explicit resummation of an infinite number of disconnected loop diagrams.
Xiaoyan Zhao🇨🇳 · Zuo-tang Liang🇨🇳 · Tianbo Liu🇨🇳 · Ya-jin Zhou🇨🇳
We investigate production in semi-inclusive deep-inelastic scattering using a polarized lepton beam and find that the spin transfer is significantly suppressed by target fragmentation. As further demonstrated by a model estimation, experimental data can be well described once the target fragmentation is taken into account, which alleviates the tension with calculations solely based on current fragmentation. Our findings suggest that, at the energies of existing fixed-target experiments, the separation of current and target fragmentation regions is not distinct. Spin transfer as well as other spin effects offers a sensitive probe into the origin of the produced hadron.
E. Richter-Was🇵🇱 · T. Yerniyazov🇵🇱 · Z. Was🇵🇱
The consecutive steps of H to tau tau cascade can be useful for the measurement of Higgs couplings and parity. The analysis methos of ATLAS and CMS Collaborations was to fit a one-dimensional distribution of the phi* angle, phi*, which is sensitive to transverse spin correlations and, hence, to the CP mixing angle, phi^CP. Machine Learning techniques (ML) offer opportunities to manage complex multidimensional signatures. The 4-momenta of the tau decay products can be used as input to the machine learning and to predict the CP-sensitive pseudo-observables and/or provide discrimination between different CP hypotheses. We show that the classification or regression methods can be used to train an ML model to predict the spin weight sensitive to the CP state of the decaying Higgs boson, parameters of the functional form of the spin weight, or the most preferred CP mixing angle of the analysed sample. The one-dimensional distribution of the predicted spin weight or the most preferred CP mixing angle of the experimental data can be examined further, with the statistical methods, to derive the measurement of the CP mixing state of the Higgs signal events. This paper extends our previous studies, with more details for the features and how proposed pseudo-observables can be used in the measurement.
Zbigniew Drogosz🇵🇱 · Wojciech Florkowski🇵🇱 · Mykhailo Hontarenko🇵🇱 · Radoslaw Ryblewski🇵🇱
Classical pseudo-gauge transformations are discussed in the context of hydrodynamic models of heavy-ion collisions. A decomposition of the pseudo-gauge transformation into Lorentz-invariant tensors is made, which allows for better interpretation of its physical consequences. For pseudo-gauge transformations connecting two symmetric energy-momentum tensors, we find that the super-potential must obey a conservation law of the form . This equation, referred to below as the STS condition, represents a constraint that is hardly possible to be satisfied for tensors constructed out of the basic hydrodynamic variables such as temperature, baryon chemical potential, and the hydrodynamic flow. However, in a special case of the boost-invariant flow, the STS condition is automatically fulfilled and a non-trivial residual pseudo-gauge transformation defined by a single scalar field is allowed. In this case the bulk and shear viscosity coefficients become pseudo-gauge dependent; however, their specific linear combination appearing in the equations of motion remains pseudo-gauge invariant. This finding provides new insights into the role of pseudo-gauge transformations and pseudo-gauge invariance.
Eduardo Lourenço Fabio de Lima🇧🇷
This work delves into the study of flavor invariants and, in special, invariants capable of detecting CP (Charge-Parity) violation. Through the mathematical tool of the Hilbert series, we systematically enumerate and explore flavor invariants that are unchanged under weak basis transformations. After reviewing the Hilbert series and the flavor invariants of the SM quark sector, we apply the tool of Hilbert series to the SM extended by a singlet vector-like quark (VLQ) of down-type. The introduction of these hypothetical particles leads to a simple extension of the SM that can be motivated by many problems, including the need for new sources of CP violation to explain the observed matter-antimatter asymmetry in the universe. We were successful in calculating the Hilbert series for the VLQ extension in the mass basis of the VLQ, where the spurion transformations are simpler. Based on the Hilbert series, we build and enumerate the basic flavor invariants with which all invariants can be constructed. For a generic basis, where the spurion transformations involve a larger group, we could only get the first few terms of the Hilbert series.
The Randall-Sundrum (RS) model offers a compelling framework to address the hierarchy problem and provides new sources of CP violation beyond the Standard Model (SM). The motivation for studying CP violation in the RS model arises from the insufficiency of CP-violating phases in the SM to account for the observed matter-antimatter asymmetry in the universe. In this work, we explore CP violation through flavour-violating di-Higgs couplings, which emerge due to the localization of bulk fermions and the Higgs near the TeV brane. The analysis focuses on the role of these couplings in di-Higgs production and decay processes, leading to enhanced CP-violating effects. Numerical simulations show that the predicted CP-violating observables are within experimental bounds and could be tested in future collider experiments. The study concludes that flavour-violating di-Higgs couplings in the RS model offer a promising avenue for discovering new sources of CP violation, with significant implications for both collider physics and the understanding of the matter-antimatter asymmetry.
Kodai Sakurai🇯🇵 · Fuminobu Takahashi🇯🇵
We discuss the thermal production of axions in renormalizable models involving two Higgs doublet fields and a complex singlet field with a global Peccei-Quinn symmetry, i.e., DFSZ type axion models. We demonstrate that, when the reheating temperature exceeds the mass scale of heavy Higgs bosons, axions are efficiently produced through heavy Higgs boson decays and scatterings at temperatures comparable to the heavy Higgs boson mass scale. As a result, the abundance of thermally produced axions is independent of the reheating temperature, which should be contrasted with the KSVZ axion model. This is because thermal productions via renormalizable interactions are IR-dominated processes. We demonstrate that the heavy Higgs boson decays are the main channels for axion thermal productions among various processes in the DFSZ-type axion models, which were missed in the literature. Our results apply to the original DFSZ QCD axion model since the production mechanism does not depend on the axion mass. As an application of axion productions from the heavy Higgs boson decays, we calculate the contributions to for axions with a mass smaller than . Future measurements of could constrain model parameters in both axion and Higgs sectors. Focusing on axions with masses from keV to sub-GeV scale, we then discuss how cosmological observations such as X-ray and cosmic microwave background constrain the produced axion. We show that a large portion of the parameter space of the models can be explored even if the amount of the axion produced from the heavy Higgs bosons is much smaller than the observed cold dark matter abundance.
Detecting Beyond Standard Model (BSM) signals in high-energy particle collisions presents significant challenges due to complex data and the need to differentiate rare signal events from Standard Model (SM) backgrounds. This study investigates the efficacy of deep learning models, specifically Deep Neural Networks (DNNs) and Graph Neural Networks (GNNs), in classifying particle collision events as either BSM signal or background. The research utilized a dataset comprising 214,000 SM background and 10,755 BSM events. To address class imbalance, an undersampling method was employed, resulting in balanced classes. Three models were developed and compared: a DNN and two GNN variants with different graph construction methods. All models demonstrated high performance, achieving Area Under the Receiver Operating Characteristic curve (AUC) values exceeding . While the DNN model slightly outperformed GNNs across various metrics, both GNN approaches showed comparable results despite different graph structures. The GNNs' ability to explicitly capture inter-particle relationships within events highlights their potential for BSM signal detection.
Charmonia suppression has been considered as a smoking gun signature of quark-gluon plasma. However, the Large Hadron Collider has observed a lower degree of suppression as compared to the Relativistic Heavy Ion Collider energies, due to regeneration effects in heavy-ion collisions. Though proton collisions are considered to be the baseline measurements to characterize a hot and dense medium formation in heavy-ion collisions, LHC proton collisions with its new physics of heavy-ion-like QGP signatures have created new challenges. To understand this, the inclusive charmonia production at the forward rapidities in the dimuon channel is compared with the corresponding measurements in the dielectron channel at the midrapidity as a function of final state charged particle multiplicity. None of the theoretical models quantitatively reproduce the experimental findings leaving out a lot of room for theory. To circumvent this and find a reasonable understanding, we use machine learning tools to separate prompt and nonprompt charmonia and open charm mesons using the decay daughter track properties and the decay topologies of the mother particles. Using PYTHIA8 data, we train the machine learning models and successfully separate prompt and nonprompt charm hadrons from the inclusive sample to study various directions of their production dynamics. This study enables a domain of using machine learning techniques, which can be used in the experimental analysis to better understand charm hadron production and build possible theoretical understanding.
Wolfgang Altmannshofer🇺🇸 · Shibasis Roy🇮🇳
In light of the recent branching fraction measurement of the decay by Belle II and its poor agreement with the SM expectation, we analyze the effects of an axion-like particle (ALP) in meson decays. We assume a long-lived ALP with a mass of the order of the pion mass that decays to two photons. We focus on a scenario where the ALP decay length is of the order of meters such that the ALP has a non-negligible probability to decay outside the detector volume of Belle II, mimicking the signal. Remarkably, such an arrangement is also relevant for the long-standing puzzle by noting that the measured and decays could have a and component, respectively. We also argue based on our results that the required ALP-photon effective coupling belongs to a region of parameter space that can be extensively probed in future beam dump experiments like SHiP.
Genessa Benton🇺🇸 · Diogo Boito🇧🇷 · Maarten Golterman🇺🇸 · Alexander Keshavarzi🇬🇧 · Kim Maltman🇨🇦 · Santiago Peris🇪🇸
A key issue affecting the attempt to reduce the uncertainty on the Standard Model prediction for the muon anomalous magnetic moment is the current discrepancy between lattice-QCD and data-driven results for the hadronic vacuum polarization. Progress on this issue benefits from precise data-driven determinations of the isospin-limit light-quark-connected (lqc) and strange-plus-light-quark-disconnected (s+lqd) components of the related RBC/UKQCD windows. In this paper, using a strategy employed previously for the intermediate window, we provide data-driven results for the lqc and s+lqd components of the short- and long-distance RBC/UKQCD windows. Comparing these results with those from the lattice, we find significant discrepancies in the lqc parts but good agreement for the s+lqd components. We also explore the impact of recent CMD-3 cross-section results, demonstrating that an upward shift in the -peak region of the type seen in the CMD-3 data serves to eliminate the discrepancies for the lqc components without compromising the good agreement between lattice and data-driven s+lqd results.
Shinsuke Kawai🇰🇷 · Nobuchika Okada🇺🇸
We investigate the flavour sector of the supersymmetric Grand Unified Theory (GUT) model using machine learning techniques. The minimal model is known to predict fermion masses that disagree with observed values in nature. There are two well-known approaches to address this issue: one involves introducing a 45-representation Higgs field, while the other employs a higher-dimensional operator involving the 24-representation GUT Higgs field. We compare these two approaches by numerically optimising a loss function, defined as the ratio of determinants of mass matrices. Our findings indicate that the 24-Higgs approach achieves the observed fermion masses with smaller modifications to the original minimal model.
Rui Gao🇨🇳 · Jin Hao🇨🇳 · Chun-Gui Duan🇨🇳 · Zhi-Hui Guo🇨🇳 · J.A.Oller🇪🇸 · Hai-Qing Zhou🇨🇳
We pursue the calculation of the model-independent component of the axion-photon-photon coupling in the chiral perturbation theory up to next-to-leading order, with the emphasis on the isospin breaking effect. The mixing of the ---axion system is revised as well by working out the complete linear isospin-breaking terms. Our calculation shows that the isospin-breaking correction to the axion-photon-photon coupling amounts to more than 15%, comparing with the result in the isospin limit.
Jing-Jing Zhang🇫🇷 · Zhi-Long Han🇨🇳 · Ang Liu🇨🇳 · Feng-Lan Shao🇨🇳
The new gauge boson in is widely considered as the mediator of dark matter. In this paper, we propose the conversion-driven dark matter in . The dark sector contains two Dirac fermions and with charge 0 and , respectively. A symmetry is also introduced to ensure the stability of dark matter. The mass term induces the mixing of dark fermion. Then the lightest dark fermion becomes the dark matter candidate, whose coupling to is suppressed by the mixing angle . Instead of freezing-out via pair annihilation, we show that the observed relic abundance can be obtained through the conversion processes. We then explore the feasible parameter space of conversion-driven dark matter in . Under various experimental constraints, the conversion-driven dark matter prefers the region with and ~GeV, which is within the reach of future Belle II, FASER and SHiP.
Tingting Dai🇨🇳 · Huiqiang Ding🇨🇳 · Luan Cheng🇨🇳 · Weining Zhang🇨🇳 · Enke Wang🇨🇳
We investigate the boundary effect of QGP droplet and self-similarity effect of hadrons on QGP-hadron phase transition. In intermediate or low energy collisions, when the transverse momentum is below QCD scale, QGP cannot be produced. However, if the transverse momentum fluctuates to a relatively large value, small scale QGP droplet is produced. The modified MIT bag model with multiple reflection expansion method is employed to study the QGP droplet with the curved boundary effect. It is found that the energy density, entropy density and pressure of QGP with the influence are smaller than those without the influence. In hadron phase, we propose Two-Body Fractal Model (TBFM) to study the self-similarity structure, arising from the resonance, quantum correlation and interaction effects. It is observed that energy density, entropy density and pressure increase due to the self-similarity structure. We calculate the transverse momentum spectra of pions with the self-similarity structure influence, showing a good agreement with the experimental data. Considering both the boundary effect and self-similarity structure influence, our model predicts an increase in the transition temperature compared to scenarios without these two effects in HIAF energy region .
This article revisits the validity of tree-level statements regarding the Yukawa sector of various minimal-renormalisable \(SU(5)\) frameworks at the loop level. It is well-known that an \(SU(5)\) model with only the \(45_{\mathrm{H}}\) dimensional irreducible representation~(irrep) contributing to the Yukawa sector is highly incompatible in yielding the low-energy observables. However, this study shows that when one-loop corrections from heavy degrees of freedom are included in the various Yukawa vertices, the model can reproduce the charged fermion mass spectrum and mixing angles within the assumed experimental uncertainty. The fitted Yukawa couplings remain within the perturbative range. The scenario also necessitates mass splitting among various scalars of dimensional irrep, with some of the scalars' mass deviating significantly from the matching scale \((M_{GUT})\), collectively providing substantial threshold corrections. The effect of the lightest scalar on the RGE evolution of the SM parameters has also been considered. It is shown that this scenario reproduces the SM spectrum at low energy. As an extension, the minimal \(SU(5)\) model with only the \(45_{\mathrm{H}}\) irrep is augmented with the \(15_{\mathrm{H}}\)-dimensional irrep, which also successfully reproduces the observed charged and neutral fermion mass spectra. Finally, the study considers an alternative \(SU(5)\) model incorporating both \(5_{\mathrm{H}}\) and \(15_{\mathrm{H}}\) irreps, which also yields the desired fermion mass spectra and mixing angles. This work demonstrates the viability of a minimal \(SU(5)\) Yukawa sector in different setups when quantum corrections are considered.
Shohini Bhattacharya🇺🇸 · Yoshitaka Hatta🇺🇸 · Jakob Schoenleber🇺🇸
We discuss the nonlocal generalization of the QCD chiral anomaly along the light-cone and derive relations between twist-two, twist-three and twist-four generalized parton distributions (GPDs) mediated by the anomaly. We further establish the connection to the `anomaly pole' in the GPD recently identified in the perturbative calculation of the Compton scattering amplitudes, and demonstrate its cancellation at the GPD level. Our work helps elucidate the previously unexplored connection between GPDs, the chiral anomaly, and the mass generation of the meson.
Linlin Huang🇨🇳 · Mamiya Kawaguchi🇨🇳 · Yadikaer Maitiniyazi🇨🇳 · Shinya Matsuzaki🇨🇳 · Akio Tomiya🇯🇵 · Masatoshi Yamada🇨🇳
We perform a functional renormalization group analysis of a four-fermion model with and violation to explore the nonperturbative infrared dynamics of quantum chromodynamics (QCD) within the Wilsonian renormalization group framework, particularly in the context of spontaneous -violation models. Our analysis of the fixed-point structure reveals that, in the large- limit, the -violating parameter is dynamically induced and approaches (where is the number of flavors) as the system enters the chirally broken phase. This behavior arises due to criticality and the large anomalous dimensions of the -violating four-fermion couplings. Furthermore, this trend appears to persist beyond the leading large- approximation, provided that the infrared dynamics of QCD remains dominated by the scalar condensate of the quark bilinear, as expected. Notably, our findings highlight that -violating four-fermion interactions, which are perturbatively irrelevant, can become relevant in the chirally broken phase through nonperturbative effects, with potential implications for spontaneous -violation scenarios.
Luis A. Anchordoqui🇺🇸 · Ignatios Antoniadis🇹🇭 · Dieter Lust🇩🇪 · Karem Peñaló Castillo🇺🇸
We reexamine a dynamical dark matter model with Kaluza-Klein (KK) towers of gravitons and neutrinos fitting together in the dark dimension. We show that even though gravitational decays of neutrino KK towers have little impact in cosmology the weak decay channel could have significant cosmological effects. Taking conservative upper bounds on the dark matter decay rate into two photons before recombination and on the number of effective extra neutrino species we derive constraints on the conversion rate from active to sterile species despite the dependence of the mixing angle on the KK mode mass. We also provide counterarguments to a recent claim suggesting that the bounds on rule out micron-sized extra dimensions.
As a straightforward application of the recently calculated two-loop heavy quarkonium Hamiltonian, we evaluate the two-loop term of the heavy quarkonium potential. Compared to a previous calculation we find a small difference in the coefficient of the maximally non-abelian color factor . We further examine this coefficient carefully.
Thomas Dave🇬🇧 · William J. Torres Bobadilla🇬🇧
We analytically calculate one- and two-loop helicity amplitudes in massless QED, by adopting a four-dimensional tensor decomposition. We draw our attention to four-fermion and Compton scattering processes to higher orders in the dimensional regulator, as required for theoretical predictions at NLO. We organise loop amplitudes by proposing an efficient algorithm at integrand level to group Feynman graphs into integral families. We study the singular structure of these amplitudes and discuss the correspondence between QED and QCD processes. We present our results in terms of generalised polylogarithms up to transcendental weight six.
Wei Wang🇨🇳 · Ji Xu🇨🇳 · Qi-An Zhang🇨🇳 · Shuai Zhao🇨🇳
The heavy meson light-cone distribution amplitude (LCDA), as defined in full QCD, plays a key role in the collinear factorization for exclusive heavy meson production and in lattice computations of the LCDA within heavy-quark effective theory (HQET). In addition to its dependence on the renormalization scale, the QCD LCDA also evolves with the heavy quark mass. We derive a partial differential equation to characterize the mass evolution of the heavy meson QCD LCDA, examining the heavy quark mass dependence through its solution. Our results link the internal structure of heavy mesons across different quark masses, offering significant implications for lattice calculations and enabling the extrapolation of results from lower to higher quark masses.
Emilio J. Estrada🇲🇽 · Juan Manuel Márquez🇲🇽 · Diego Portillo-Sánchez🇲🇽 · Pablo Roig🇲🇽
We analyze the protonbox contribution to the hadronic lightbylight part of the muon's anomalous magnetic moment, which is the first reported baryonic contribution to this piece. We follow the quarkloop analysis, incorporating the relevant datadriven and lattice proton form factors. Although the heavy mass expansion would yield a contribution of , the damping of the form factors in the regions where the kernel peaks, explains our finding , two orders of magnitude smaller than the forthcoming uncertainty on the measurement and on its Standard Model prediction.
Jason Aebischer🇨🇭 · Tejhas Kapoor🇫🇷 · Jacky Kumar🇺🇸
Sterile neutrinos are well-motivated beyond the Standard Model (BSM) particles. The Standard Model Effective Field Theory (SMEFT) augmented with these new fields is known as the SMEFT. We present the first code for solving the renormalization group equations (RGEs) of the SMEFT in an automated way. For this purpose, we have implemented the SMEFT as a new effective field theory (EFT) in the Wilson coefficient exchange format WCxf. Furthermore, we included anomalous dimensions depending on the gauge couplings and Yukawas in the python package wilson. This novel version of wilson allows a consistent inclusion of SMEFT renormalization group (RG) running effects above the electroweak (EW) scale in phenomenological studies involving sterile neutrinos. Moreover, this new release allows us to study EW, strong, and Yukawa running effects separately within the SMEFT.
Bohdan Grzadkowski🇵🇱 · Anna Socha🇫🇷
A quantum theory of massive Abelian vector bosons with non-minimal couplings to gravity has been studied within an evolving, isotropic, and homogeneous gravitational background. The vectors may play a role of dark matter if stabilizing symmetry is imposed. In order to construct a gauge invariant theory of massive vectors that couple to the Ricci scalar and Ricci tensor, a generalization of the Stuckelberg mechanism has been invoked. Constraints that ensure consistency of the model had been formulated and corresponding restrictions upon the space of non-minimal couplings have been found. Canonical quantization of the theory in evolving gravitational background was adopted. Mode equations for longitudinally and transversally-polarized vector bosons were derived and solved numerically. Regions of exponential growth in the solutions of the mode equations have been determined and discussed in detail. The spectral energy density for the three polarizations has been calculated, and the UV divergence of the integrated total energy density has been addressed. Finally, assuming their stability, the present abundance of the vector bosons has also been calculated.
Paulina Knees🇦🇷 · Essodjolo Kpatcha🇪🇸 · Iñaki Lara🇵🇱 · Daniel E. López-Fogliani🇦🇷 · Carlos Muñoz🇪🇸
We analyse relevant signals expected at the LHC for a squark of the first two families as the lightest supersymmetric particle (LSP). The discussion is established in the framework of the SSM, where the presence of -parity violating couplings involving right-handed neutrinos solves simultaneously the -problem and the accommodation of neutrino masses and mixing angles. The squarks are pair produced and decay dominantly to a neutrino and a quark. They also have two sub-dominant three body decays to quark, Higgs and neutrino/charged lepton. The decays can be prompt or displaced, depending on the regions of the parameter space of the model. We focus the analyses on squarks of right up-type, right down-type, and left up-type; since squarks of left down-type cannot be the LSP because of D-term contributions. We compare the predictions of these scenarios with ATLAS and CMS searches for prompt and long-lived particles. To analyse the parameter space we sample the SSM for a squark LSP, paying special attention to reproduce the current experimental data on neutrino and Higgs physics, as well as flavour observables. Because of the contribution of squark-squark final states to the production cross section, the results depend on the squark family. In particular, for a right strange squark LSP, the lower limit on the mass is GeV, corresponding to an upper limit on the decay length of mm, and for a right (left) scharm LSP, the limits are () GeV and () mm. However, the first family of squarks as LSP turns out to be excluded, unless the gluino is heavier than TeV, which produces a limit on the squark mass of GeV.
Brian Batell🇺🇸 · Amit Bhoonah🇺🇸 · Wenjie Huang🇺🇸
Heavy right-handed neutrinos are highly motivated due to their connection with the origin of neutrino masses via the seesaw mechanism. If the right-handed neutrino Majorana mass is at or below the weak scale, direct experimental discovery of these states is possible in laboratory experiments. However, there is no a priori basis to expect right-handed neutrinos to be so light since the Majorana mass is a technically natural parameter and could comfortably reside at any scale, including at scales far above the weak scale. Here we explore the possibility that the right-handed neutrino Majorana mass originates from electroweak symmetry breaking. Working within an effective theory with two Higgs doublets, nonzero lepton number is assigned to the bilinear operator built from the two Higgs fields, which is then coupled to the right-handed neutrino mass operator. In tandem with the neutrino Yukawa coupling, following electroweak symmetry breaking a seesaw mechanism operates, generating the light SM neutrino masses along with right-handed neutrinos with masses below the electroweak scale. This scenario leads to novel phenomenology in the Higgs sector, which may be probed at the LHC and at future colliders. There are also interesting prospects for neutrinoless double beta decay and lepton flavor violation. We also explore some theoretical aspects of the scenario, including the technical naturalness of the effective field theory and ultraviolet completions of the right-handed neutrino Majorana mass.
Tian Lin🇨🇳 · Mattia Bruno🇮🇹 · Xu Feng🇨🇳 · Lu-Chang Jin🇺🇸 · Christoph Lehner🇩🇪 · Chuan Liu🇨🇳 · Qi-Yuan Luo🇨🇳
We develop a method to compute the pion transition form factor directly at arbitrary space-like photon momenta and use it to determine the -pole contribution to the hadronic light-by-light scattering in the anomalous magnetic moment of the muon. The calculation is performed using eight gauge ensembles generated with 2+1 flavor domain wall fermions, incorporating multiple pion masses, lattice spacings, and volumes. By introducing a pion structure function and performing a Gegenbauer expansion, we demonstrate that about 98\% of the -pole contribution can be extracted in a model-independent manner, thereby ensuring that systematic effects are well controlled. After applying finite-volume corrections, as well as performing chiral and continuum extrapolations, we obtain the final result for the -pole contribution to the hadronic light-by-light scattering in the muon's anomalous magnetic moment, , and the decay width, eV.
Peng-Ju Wu🇨🇳 · Xin Zhang🇨🇳
The cosmic curvature is an important parameter related to the inflationary cosmology and the ultimate fate of the universe. In this work, we adopt the non-CMB observations to constrain in the CDM model and its extensions. The DESI baryon acoustic oscillation, DES type Ia supernova, cosmic chronometer, and strong gravitational lensing time delay data are considered. We find that the data combination favors an open universe in the CDM model, specifically at the confidence level, which is in tension with the Planck CMB result supporting our universe being slightly closed. In the CDM extensions, the data combination is consistent with a spatially flat universe. However, the central value of is positive and has a significant deviation from zero. We adopt the Akaike information criterion to compare different cosmological models. The result shows that non-flat models fit the observational data better than the flat CDM model, which adds evidence to the argument that flat CDM is not the ultimate model of cosmology.
Joan Solà Peracaula🇪🇸 · Cristian Moreno-Pulido🇪🇸
The cosmological constant term (CC), , is a pivotal ingredient in the standard model of cosmology or CDM, but it is a rigid quantity for the entire cosmic history. This is unnatural and inconsistent. Different theoretical and phenomenological conundrums suggest that the CDM necessitates further theoretical underpinning to cope with modern observations. An interesting approach is the framework of the `running vacuum model' (RVM). It endows with cosmic dynamics within a fundamental framework since it is based on QFT. In the RVM, the vacuum energy density (VED) appears as a series of powers of the Hubble function and its derivatives, . In the current universe, changes as . Higher order effects , on the other hand, can be responsible for a new mechanism of inflation (RVM-inflation). On the practical side the RVM can alleviate the cosmological tensions on and . An intriguing smoking gun signature of the RVM is that its equation of state can mimic quintessence, as recently observed by DESI, so the vacuum can be the sought-for dynamical DE. At a deeper theoretical level, the RVM-renormalized form of the VED can avoid extreme fine tuning related to the well-known cosmological constant problem. Overall, the RVM has the capacity to impinge positively on relevant theoretical and practical aspects of modern cosmology.
Cheng-Jun Xia🇨🇳 · Yu-Ting Rong🇨🇳 · Ting-Ting Sun🇨🇳
We propose a new theoretical framework to investigate the properties of finite nuclei based on an extended Nambu-Jona-Lasinio (eNJL) model, where the Dirac sea, the spontaneous chiral symmetry breaking, and the quark degrees of freedom are considered by extending the SU(3) NJL model and treating baryons as clusters of quarks. The eNJL model can then be readily adopted to examine the matter states ranging from baryonic matter to quark matter in a unified manner. In this work, by assuming spherically symmetric finite nuclei and neglecting the center-of-mass or rotational corrections, we systematically investigate the properties of finite nuclei based on the eNJL model with additional pairing correlations. It is found that our model generally reproduces the binding energies of the 2495 nuclei () from the 2016 Atomic Mass Evaluation (AME2016) with the root-mean-square deviations MeV. The deviations are mainly attributed to the too large shell gaps at magic numbers , 50, and 82 as well as the spurious shell closures at , 58, and 92. Meanwhile, the obtained charge radii of 906 nuclei are systematically smaller than the experimental values with root-mean-square deviations fm. In our future study, we expect to reduce the uncertainties of our predictions by carefully calibrating the density dependence of coupling constants and considering deformations with microscopic collective corrections from the nucleons in the Fermi sea and quarks in the Dirac sea.
This work applies a reduced basis method to study the continuum physics of a finite quantum system -- either few or many-body. Specifically, I develop reduced-order models, or emulators, for the underlying inhomogeneous Schrödinger equation and train the emulators against the equation's bound-state-like solutions at complex energies. The emulators rapidly and accurately interpolate and extrapolate the matrix elements of the Hamiltonian resolvent operator (Green's function) across a parameter space that includes both complex energy and other real-valued physical inputs in the Schrödinger equation. The spectra, discretized and compressed as the result of emulation, and the associated resolvent matrix elements (or amplitudes), have the defining characteristics of non-Hermitian quantum mechanics calculations, featuring complex eigenenergies with negative imaginary parts and branch cuts moved below the real axis in the complex energy plane. Therefore, one now has a method that extracts continuum physics from bound-state-like calculations and emulates those extractions in the input parameter space. Building on a prior Letter [arXiv:2408.03309], this article provides the full theoretical details, a comprehensive analysis of the method's performance, and a brief discussion of how it can be coupled with existing continuum approaches to perform emulations in their input parameter spaces.
In a multi-field/fluid cosmological system consisting of minimally coupled canonical scalar fields, non-canonical scalar fields, and barotropic perfect fluids, we introduce a new definition for the effective speed of sound of the entire system to describe the evolution of cosmological perturbations. This effective speed of sound is not only gauge-invariant but also a background-dependent quantity; it can, therefore, be treated as a parameter to quantify perturbations in such multi-field/fluid systems. It is with this effective speed that the gauge-invariant Bardeen potential and the curvature perturbation propagate at scales much smaller than the sound horizon. Furthermore, the effective speed of sound defined in this paper generalizes the one provided by Garriga and Mukhanov for a single non-canonical scalar field to a system consisting of multiple minimally coupled barotropic perfect fluids, canonical scalar fields, and non-canonical scalar fields. Moreover, as in the single pure-kinetic non-canonical scalar field case, this effective speed of sound for the total system equals the total adiabatic speed of sound when the dynamics are driven by multiple pure-kinetic non-canonical scalar fields. This makes such a system tantamount to a system of equivalent multi-barotropic perfect fluids. We also derive a set of equations governing the evolution of perturbations in a general multi-field/fluid universe. Using these equations, we demonstrate that in the large-scale limit (), initially adiabatic perturbations remain adiabatic at those scales throughout the evolution, extending this well-known result to a general multi-field/fluid system containing non-canonical scalar fields. Consequently, at those scales, such a multi-field/fluid universe dynamically behaves as if it contains only a single barotropic perfect fluid.
Peng Zhang🇨🇳 · Jing-Yuan Chen🇨🇳
Since the inception of lattice QCD, a natural definition for the Yang-Mills instanton on lattice has been long sought for. In a recent work, one of authors showed the natural solution has to be organized in terms of bundle gerbes in higher homotopy theory / higher category theory, and introduced the principles for such a categorical construction. To pave the way towards actual numerical implementation in the near future, nonetheless, an explicit construction is necessary. In this paper we provide such an explicit construction for gauge theory, with technical aspects inspired by Lüscher's 1982 geometrical construction. We will see how the latter is in a suitable sense a saddle point approximation to the full categorical construction. The generalization to will be discussed. The construction also allows for a natural definition of lattice Chern-Simons-Yang-Mills theory in three spacetime dimensions.
Rico Zöllner🇩🇪 · Burkhard Kämpfer🇩🇪
A core-corona decomposition of compact (neutron) star models is compared to recent NICER data of masses and radii. It is in particular interesting to capture the outlier XTE~J1814-338. Instead of integrating the TOV equations from the center to surface, we follow here another pathway by accommodating all uncertainties of the equation(s) of state (EoS) at supra-nuclear density or/and an unknown dark matter admixture in a parameterization of the core by its radius , the included mass and the pressure at . The corona, which may be dubbed also envelope or halo or outer crust, is assumed to be of standard-model matter where the EoS is supposed to be faithfully known.
* 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.