HEP Phenomenology·hep-ph
20 papers—13 primary·7 cross-listed·reconstructed*
Noncommutative geometry has become popular mathematics for describing speculative physics beyond the Standard Model. Noncommutative QED has long been known to fit within the framework of the Standard-Model Extension (SME). We argue in this work that noncommutative gravity also fits within the SME framework.
John M. Campbell🇺🇸 · R. Keith Ellis🇬🇧 · Satyajit Seth🇬🇧
We revisit the next-to-next-to-leading order (NNLO) calculation of the Higgs boson+1~jet production process, calculated in the effective field theory. We perform a detailed comparison of the result calculated using the jettiness slicing method, with published results obtained using subtraction methods. The results of the jettiness calculation agree with the two previous subtraction calculations at benchmark points. The performance of the jettiness slicing approach is greatly improved by adopting a definition of 1-jettiness that accounts for the boost of the Born system. Nevertheless, the results demonstrate that power corrections in the jettiness slicing method remain significant. At large transverse momentum the effect of power corrections is much reduced, as expected.
Saurabh Bansal🇺🇸 · Antonio Delgado🇺🇸 · Christopher Kolda🇺🇸 · Mariano Quiros🇪🇸
We find new limits on the R-parity violating (RPV) couplings of the minimal supersymmetric standard model, using Drell-Yan differential cross sections at the LHC and electroweak precision measurements from LEP and SLC. Specifically, limits on six out of the nine -couplings, with , are obtained using Drell-Yan data, with the remaining three (for ) bounded by precision electroweak data. We also update the limits on all -couplings using electroweak data and find new bounds on and that are stronger than obtained elsewhere. A table of all current bounds on is given in an appendix.
D. Aristizabal Sierra🇨🇱 · V. De Romeri🇪🇸 · N. Rojas🇨🇱
The presence of new neutrino-quark interactions can enhance, deplete or distort the coherent elastic neutrino-nucleus scattering (CEvNS) event rate. The new interactions may involve CP violating phases that can potentially affect these features. Assuming light vector mediators, we study the effects of CP violation on the CEvNS process in the COHERENT sodium-iodine, liquid argon and germanium detectors. We identify a region in parameter space for which the event rate always involves a dip and another one for which this is never the case. We show that the presence of a dip in the event rate spectrum can be used to constraint CP violating effects, in such a way that the larger the detector volume the tighter the constraints. Furthermore, it allows the reconstruction of the effective coupling responsible for the signal with an uncertainty determined by recoil energy resolution. In the region where no dip is present, we find that CP violating parameters can mimic the Standard Model CEvNS prediction or spectra induced by real parameters. We point out that the interpretation of CEvNS data in terms of a light vector mediator should take into account possible CP violating effects. Finally, we stress that our results are qualitatively applicable for CEvNS induced by solar or reactor neutrinos. Thus, the CP violating effects discussed here and their consequences should be taken into account as well in the analysis of data from multi-ton dark matter detectors or experiments such as CONUS, -cleus or CONNIE.
Juan V. Guerrero🇺🇸 · Alberto Accardi🇺🇸
In perturbative QCD, the masses of the hadrons involved in high energy reactions can usually be neglected. However, in the case of Kaon production in electron-proton collisions at low (and not so low) beam energies this may not be a good approximation. In particular, a recent proposal to include hadron masses in theoretical calculations shows how these Hadron Mass Corrections (HMCs) can explain a large discrepancy observed in measurements performed at the HERMES and COMPASS experiments. In this talk, we present preliminary results of a spectator model calculation designed to test the range of validity of the approximations needed in the proposed factorization scheme. We focus on inclusive DIS scattering as a first step towards the analysis of HMCs in semi-inclusive processes.
Andreas Crivellin🇨🇭 · Francesco Saturnino🇨🇭
Several experiments revealed intriguing hints for lepton flavor universality (LFU) violating new physics (NP) in semi-leptonic meson decays, mainly in and transitions at the level. Leptoquarks (LQ) are prime candidates to address these anomalies as they contribute to semi-leptonic decays already at tree level while effects in other flavor observables, agreeing with the standard model (SM), are loop suppressed. In these proceedings we review the vector leptoquark singlet, contained in the famous Pati-Salam model, which is able to address both and data simultaneously. Due to the large couplings to tau leptons needed to account for the data, sizable loop effects arise which we include in our phenomenological analysis. Updating our previous result with the recent measurements of LHCb and BELLE we find an even better fit to data than before.
We analyse the pp and pp̄ elastic scattering amplitudes using the data of several CERN and FERMILAB experiments, revisiting ideas proposed by André Martin based on analytic continuation and crossing symmetry. Introducing a new form for the scaling function together with the analytical forms from COMPETE at we show that the data are consistent with the crossing symmetry of the scattering amplitudes from 23 GeV to 13 TeV for GeV. Analiticity and crossing symmetry automatically satisfy the dispersion relations and their derivatives. The real part reproduces the zero predicted by Martin, which is crucial to describe with precision the differential cross section in the forward range at high energies. Since the free parameters of the model are energy independent, the analytical form of the amplitude allows predictions for intermediate and higher energies.
I.R. Gabdrakhmanov🇷🇺 · D. Müller🇩🇪 · O.V. Teryaev🇷🇺
The inverse Radon transform allows to obtain partonic double distributions from (extended) generalized parton distributions. We express the extension of generalized parton distributions by their dual parts, generalized distribution amplitudes and study some aspects of the filtered backprojection (inverse Radon transform). We also show that single integral transforms, previously obtained in the context of wave function overlap representation, are valid for generalized parton distributions that do not possess such a representation. Utilizing Radyushkin`s double distribution ansatz, we study and compare the numerical evaluation of double distributions within the filtered backprojection and single integral transforms along the imaginary and real axes.
We report on recent theory progress in understanding the production of heavy quarkonium in heavy-ion collisions based on the in-medium heavy-quark potential extracted from lattice QCD simulations. On the one hand, the proper in-medium potential allows us to study the spectral properties of heavy quarkonium in thermal equilibrium, from which we estimate the to ratio in heavy-ion collisions. On the other hand, the potential provides a central ingredient in the description of the real-time evolution of heavy-quarkonium formulated in the open-quantum-systems framework.
The Glashow resonance is a rapid enhancement of the cross section for scattering of electron antineutrinos on electrons at the boson production threshold due to the -channel contribution. This resonance is being searched for at large volume neutrino detectors in which the reaction to be initiated by cosmic ray antineutrinos of energies about 6.3 PeV. The relatively small neutrino flux reaching the Earth together with the necessity of analyzing ultra-high-energy final states make such searches challenging. We argue here that the Glashow resonance may contribute to the process . By extending the method of the effective (equivalent) particles to the neutral leptons, we relate the distribution of the effective neutrinos in the electron to the total cross section for . Our approach gives a good fit to existing experimental data measured at the collider LEP at CERN and allows one to interpret these measurements as an observation of the Glashow resonance. We also discuss an advantage of future electron-positron colliders for probing the resonance.
Johann Brehmer🇺🇸 · Kyle Cranmer🇺🇸 · Irina Espejo🇺🇸 · Felix Kling🇺🇸 · Gilles Louppe🇧🇪 · Juan Pavez🇨🇱
One major challenge for the legacy measurements at the LHC is that the likelihood function is not tractable when the collected data is high-dimensional and the detector response has to be modeled. We review how different analysis strategies solve this issue, including the traditional histogram approach used in most particle physics analyses, the Matrix Element Method, Optimal Observables, and modern techniques based on neural density estimation. We then discuss powerful new inference methods that use a combination of matrix element information and machine learning to accurately estimate the likelihood function. The MadMiner package automates all necessary data-processing steps. In first studies we find that these new techniques have the potential to substantially improve the sensitivity of the LHC legacy measurements.
Leila Ghasemzadeh🇮🇷 · Abolfazl Mirjalili🇮🇷 · S. Atashbar Tehrani🇮🇷
The polarized nucleon structure function in the nonsinglet case is investigated here by a new insight rather than conventional perturbative QCD (pQCD). For this purpose we note that the solution of the evolution equations in moment space involves noninteger powers of the coupling constant. Therefore it is possible to employ a new approach which is called fractional analytical perturbation theory Consequently, it is possible to remove the Landau singularities of the renormalized coupling, i.e., at the scales , using this approach. This provides an opportunity to continue the desired calculations toward small values of energy scales even less than the scale. To modify the analytical perturbation theory, a newer approach is introduced, called 2anQCD, in which the spectral function of the holomorphic coupling is parameterized in the low-energy region by two delta functions. This model gives us more reliable results for the considered QCD observables, even in the deep infrared region. We calculate the nonsinglet part of the polarized nucleon structure function, using the 2anQCD model, and compare it with the result from the underlying pQCD where both are in a new defined scheme, called the Lambert scheme. For this purpose we employ the anQCD package in the \textit{Mathematica} environment to establish the analytic (holomorphic) coupling constant. The results at various energy scales are also compared with the available experimental data, and it turns out that there is a good consistency between them. The results show that the obtained nucleon structure function at small energy scales has smoother behavior when using the 2anQCD model than the underlying pQCD. In fact the coupling constant in analytic QCD behaves moderately and it makes the result approach the available data in a better way.
Andrew J. Larkoski🇺🇸 · Eric M. Metodiev🇺🇸
Understanding jets initiated by quarks and gluons is of fundamental importance in collider physics. Efficient and robust techniques for quark versus gluon jet discrimination have consequences for new physics searches, precision studies, parton distribution function extractions, and many other applications. Numerous machine learning analyses have attacked the problem, demonstrating that good performance can be obtained but generally not providing an understanding for what properties of the jets are responsible for that separation power. In this paper, we provide an extensive and detailed analysis of quark versus gluon discrimination from first-principles theoretical calculations. Working in the strongly-ordered soft and collinear limits, we calculate probability distributions for fixed -body kinematics within jets with up through three resolved emissions (). This enables explicit calculation of quantities central to machine learning such as the likelihood ratio, the area under the receiver operating characteristic curve, and reducibility factors within a well-defined approximation scheme. Further, we relate the existence of a consistent power counting procedure for discrimination to ideas for operational flavor definitions, and we use this relationship to construct a power counting for quark versus gluon discrimination as an expansion in , the exponential of the fundamental and adjoint Casimirs. Our calculations provide insight into the discrimination performance of particle multiplicity and show how observables sensitive to all emissions in a jet are optimal. We compare our predictions to the performance of individual observables and neural networks with parton shower event generators, validating that our predictions describe the features identified by machine learning.
Gabriel Facini🇬🇧 · Kyrylo Merkotan🇩🇪 · Matthias Schott🇩🇪 · Alexander Sydorenko🇩🇪
Fiducial production cross sections measurements of Standard Model processes, in principle, provide constraints on new physics scenarios via a comparison of the predicted Standard Model cross section and the observed cross section. This approach received significant attention in recent years, both from direct constraints on specific models and the interpretation of measurements in the view of effective field theories. A generic problem in the reinterpretations of Standard Model measurements is the corrections applied to data to account for detector effects. These corrections inherently assume the Standard Model to be valid, thus implying a model bias of the final result. In this work, we study the size of this bias by studying several new physics models and fiducial phase-space regions. The studies are based on fast detector simulations of a generic multi-purpose detector at the Large Hadron Collider. We conclude that the model bias in the associated reinterpretations is negligible only in specific cases. An evaluation of potential migration effects, as well as a precise definition of the final state signatures, has to be performed before any new physics reinterpretation effort.
Jun Li🇨🇳 · Qing-Guo Huang🇨🇳
We update the constraints on the power spectra of primordial curvature perturbation and tensor perturbation including Planck data 2015 (P15) and recently released BICEP2/Keck data (BK15), Baryon Acoustic Oscillation data and the Type Ia supernovae data. We find that the upper limits of tensor-to-scalar ratio are , and at confidence level (CL) in the CDM+, CDM++ and CDM+++ models respectively, where and are the running of scalar spectral index and running of running. The inflation model with a concave potential is favored at more than CL. In addition, parametrizing the slow-roll parameter , where is the e-folding number before the end of inflation and taken in the range of and respectively, we conclude that the inflation model with a monomial potential is disfavored at more than CL, and both the Starobinsky inflation model and brane inflation model are still consistent with the data.
By comparing the two- and three-flavor Nambu--Jona-Lasinio (NJL) models, we demonstrate that the naively expected vacuum superconductivity (VSC) in constant magnetic field is disfavored due to the splitting magnetic catalysis effect (MCE) to chiral condensates with different quark flavors. Based on the simple two-flavor NJL model, we illuminate, in the lowest Landau level approximation, the similar origins of and ( meson with spin ) mass reductions with smaller and their different features at larger . With the full Landau levels, the two-flavor NJL model is found to be invalid to study the magnetic field effect to meson with physical vacuum mass . Then, restricted to meson mass below two-quark threshold in vacuum, that is , it is found that mass decreases and then increases with slowly, and mass vanishing point is delayed to larger compared to the point particle result. In the more realistic three-flavor NJL model, all the quark masses split in strong magnetic field as a combinatorial result of their different current masses and electric charges. By choosing a vacuum mass closer to the physical one, meson mass is found to be consistent with the LQCD results semi-quantitatively in smaller region but increase in larger region. These features are mainly outcomes of the interplay between the coupling effect and splitting MCE to the composite and quarks, which definitely disfavors VSC when the latter dominates. Furthermore, mesonic flavor mixing is modified by among the neutral pseudoscalars: and , which is very important to suppress the mass enhancement of the effective mass eigenstates at large .
Stefano Bolognesi🇮🇹 · Kenichi Konishi🇮🇹
Dynamics and symmetry realization in various chiral gauge theories in four dimensions are investigated, generalizing a recent work by M. Shifman and the present authors, by relying on the standard 't Hooft anomaly matching conditions and on some other general ideas. These requirements are so strong that the dynamics of the systems are severely constrained. Color-flavor or color-flavor-flavor locking, dynamical Abelianization, and combinations of these, are powerful ideas which often leads to solutions of the anomaly matching conditions. Moreover, a conjecture is made on generation of a mass hierarchy associated with symmetry breaking in chiral gauge theories, which has no analogues in vector-like gauge theories such as QCD.
Tommy Ohlsson🇸🇪 · Shun Zhou🇨🇳
We investigate how to define in a consistent way the probabilities of the transitions between the "flavor" states of the two-level quantum system, which is described by a non-Hermitian but parity and time-reversal (PT) symmetric Hamiltonian. Explicit calculations are carried out to demonstrate the conservation of probability if a proper definition of the final state is adopted. Finally, this formalism is applied to two-flavor neutrino oscillations and in vacuum, where the exact PT symmetry requires the vacuum mixing angle to be maximal, which is compatible with current neutrino oscillation experiments. A possible generalization to the three-flavor case is briefly discussed.
Andrea Cristofoli🇩🇰 · N.E.J. Bjerrum-Bohr🇩🇰 · Poul H. Damgaard🇩🇰 · Pierre Vanhove🇫🇷
We describe the computation of post-Minkowskian Hamiltonians in General Relativity from scattering amplitudes. Using a relativistic Lippmann-Schwinger equation, we relate perturbative amplitudes of massive scalars coupled to gravity to the post-Minkowskian Hamiltonians of classical General Relativity to any order in Newton's constant. We illustrate this by deriving an Hamiltonian for binary black holes without spin up to 2nd order in the post-Minkowskian expansion and demonstrate explicitly the equivalence with the recently proposed method based on an effective field theory matching.
Matías Fernández🇺🇾 · Marcela Peláez🇺🇾
We investigate the influence of the different vertices of two-point correlation functions in the infrared regime of Yang-Mills theory using a phenomenological description. This regime is studied in Landau-gauge and using perturbation theory within a phenomenological massive model. We perform a one-loop calculation for two-point correlation functions taking into account the different role of the various interactions in the infrared. Our results show a good agreement with the lattice data.
* 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.