HEP Phenomenology·hep-ph
24 papers—18 primary·6 cross-listed·reconstructed*
Gil Paz🇺🇸
Effective field theories such as Heavy Quark Effective Theory (HQET) are indispensable tools in controlling the effects of the strong interaction. The increasing experimental precision requires the knowledge of higher dimensional operators. We present a general method that allows for an easy construction of HQET operators that contain two heavy quarks and any number of covariant derivatives.
Gil Paz🇺🇸
This talk discusses the theory of inclusive and exclusive radiative B decays, emphasizing the interplay of perturbative and non-perturbative effects and the importance CP and isospin asymmetries.
Hiren H. Patel🇺🇸 · Branimir Radovcic🇩🇪
In this paper, we numerically study the impact heavy field degrees of freedom have on vacuum metastability in a toy model, with the aim of better understanding how the decoupling theorem extends to semiclassical processes. We observe that decoupling applies to partial amplitudes associated with fixed final state field configurations emerging from the tunneling processes, characterized by a scale such as the inverse radius of a spherically symmetric bubble, and not directly on the total lifetime (as determined by the "bounce"). More specifically, tunneling amplitudes for bubbles with inverse radii smaller than the scale of the heavier fields are largely insensitive to their presence, while those for bubbles with inverse radii larger than that scale may be significantly modified.
The work is a brief review of the theory based on the gauge group in the presence of Heavy Leptons. Recent analysis have established a set of four possible variants for the 3-3-1HL, whose content arises according to the so-denoted variable . Since it has been argued about the presence of stable charged particles in this sort of models, we divide the different sectors of the Lagrangian between universal and specific vertices, and conclude that the omission of -dependent terms in the potential may induce to a discrete symmetry for the versions defined by . In the context of , where the new degrees of freedom have the same standard electric charges, additional Yukawa interactions may create decay channels into the SM sector. Furthermore, we introduce a method of diagonalization by parts in the Scalar sector motivated by a general consequence of the Goldstone theorem. In summary, we develop the most complete set of terms allowed by the symmetry group and resolve their definitive pieces in order to justify the model description present in the literature.
We revisit the radiative decays of the Higgs boson to a fermion pair where denotes a fermion in the Standard Model (SM). We include the chirality-flipping diagrams via the Yukawa couplings at the order , the chirality-conserving contributions via the top-quark loops of the order , and the electroweak loops at the order . The QED correction is about and contributes to the running of fermion masses at a similar level, which should be taken into account for future precision Higgs physics. The chirality-conserving electroweak-loop processes are interesting from the observational point of view. First, the branching fraction of the radiative decay is about a half of that of , and that of is more than four orders of magnitude larger than that of , both of which reach about . The branching fraction of is of the order . All the leptonic radiative decays are potentially observable at the LHC Run 2 or the HL-LHC. The kinematic distributions for the photon energy or the fermion pair invariant mass provide non-ambiguous discrimination for the underlying mechanisms of the Higgs radiative decay. We also study the process and evaluate the observability at the LHC. We find it comparable to the other related studies and better than the channel in constraining the charm-Yukawa coupling.
Anirban Biswas🇮🇳 · Sandhya Choubey🇮🇳 · Sarif Khan🇮🇳
The Standard Model (SM) is inadequate to explain the origin of tiny neutrino masses, the dark matter (DM) relic abundance and also the baryon asymmetry of the Universe. In this work to address all the three puzzles, we extend the SM by a local U gauge symmetry, three right-handed (RH) neutrinos for the cancellation of gauge anomalies and two complex scalars having nonzero U charges. All the newly added particles become massive after the breaking of U symmetry by the vacuum expectation value (VEV) of one of the scalar fields . The other scalar field , which does not have any VEV, becomes automatically stable and can be a viable DM candidate. Neutrino masses are generated using Type-I seesaw mechanism while the required lepton asymmetry to reproduce the observed baryon asymmetry, can be attained from the CP violating out of equilibrium decays of RH neutrinos in TeV scale. More importantly within this framework, we have studied in detail the production of DM via freeze-in mechanism considering all possible annihilation and decay processes. Finally, we find a situation when DM is dominantly produced from the annihilation of RH neutrinos, which are at the same time also responsible for neutrino mass generation and leptogenesis.
Arindam Das🇰🇷 · P. S. Bhupal Dev🇺🇸 · C. S. Kim🇰🇷
We use the LHC Higgs data to derive updated constraints on electroweak-scale sterile neutrinos that naturally occur in many low-scale seesaw extensions of the Standard Model to explain the neutrino masses. We also analyze the signal sensitivity for a new final state involving a single charged lepton and two jets with missing energy, which arises from the decay of sterile neutrinos produced through the Higgs and boson mediated processes at the LHC. Future prospects of these sterile neutrino signals in precision Higgs measurements, as well as at a future 100 TeV collider, are also discussed.
Arindam Das🇰🇷 · Yu Gao🇺🇸 · Teruki Kamon🇺🇸
In the inverse see-saw model the effective neutrino Yukawa couplings can be sizable due to a large mixing angle between the light and heavy neutrinos . When the right handed neutrino can be lighter than the Standard Model (SM) Higgs boson . It can be produced via the on-shell decay of the Higgs, at a significant branching fraction at the LHC. In such a process mass can be reconstructed in its dominant decays. We perform an analysis on this channel and its relevant backgrounds, among which the jets background is the largest. Considering the existing mixing constraints from the Higgs and electroweak precision data, the best sensitivity of the heavy neutrino search is achieved for benchmark mass at 100 and 110 GeV for upcoming high luminosity LHC runs.
Stefan Gieseke🇩🇪 · Patrick Kirchgaeßer🇩🇪 · Frasher Loshaj🇩🇪
We present a new model for soft interactions in the Monte Carlo event-generator Herwig. The soft diffractive final states are modeled on the basis of the cluster hadronization model and interactions between soft particles are modeled as multiple particle production with multiperipheral kinematics. We further present much improved results of mininum-bias measurements at different energies.
James Currie🇬🇧 · E.W.N. Glover🇬🇧 · Aude Gehrmann-De Ridder🇨🇭 · Thomas Gehrmann🇨🇭 · Alexander Huss🇨🇭 · Joao Pires🇩🇪
We study the single jet inclusive cross section up to next-to-next-to leading order in perturbative QCD, implemented in the parton-level event generator NNLOJET . Our results are fully differential in the jet transverse momentum and rapidity and we apply fiducial cuts for comparison with the available ATLAS 7 TeV 4.5 fb data for jet radius . For the theoretical calculation we employ the antenna subtraction method to reliably cancel all infrared divergences present at intermediate stages of the calculation. We present all results using the individual jet transverse momentum as the renormalization and factorization scale for each jet's contribution to the single jet inclusive cross section. Finally, we consider the differences between our predictions using this scale choice to those for the leading jet transverse momentum scale choice, , used in [14], with reference to the ATLAS data.
The CLAS Collaboration recently reported measured ratios of pion and kaon electroproduction cross sections from a proton target and extracted the ratios for light and strange quark--antiquark pairs, and . Within an extended chiral constituent quark formalism, we investigate contributions to those ratios from the nonperturbative mechanism due to all possible intrinsic Fock states in the proton; with . Our results are compared with the CLAS data and findings from other phenomenological approaches, offering insights into the manifestations of the genuine five--quark Fock states in the proton and its relevance to interpreting the experimental data.
M. Kuroda🇯🇵 · D. Schildknecht🇩🇪
We investigate the mass range of the quark-antiquark fluctuations of the photon that are active in producing the total photoabsorption cross section in the color dipole picture, emphasizing the notion of color transparency and saturation. We consider the implications of measurements at future extensions of the available electron-proton-scattering energy.
A. Lopez-Eiguren🇪🇸 · J. Urrestilla🇪🇸 · A. Achúcarro🇪🇸 · A. Avgoustidis🇬🇧 · C. J. A. P. Martins🇵🇹
We continue a comprehensive numerical study of semilocal string networks and their cosmological evolution. These can be thought of as hybrid networks comprised of (non-topological) string segments, whose core structure is similar to that of Abelian Higgs vortices, and whose ends have long--range interactions and behaviour similar to that of global monopoles. Our study provides further evidence of a linear scaling regime, already reported in previous studies, for the typical length scale and velocity of the network. We introduce a new algorithm to identify the position of the segment cores. This allows us to determine the length and velocity of each individual segment and follow their evolution in time. We study the statistical distribution of segment lengths and velocities for radiation- and matter-dominated evolution in the regime where the strings are stable. Our segment detection algorithm gives higher length values than previous studies based on indirect detection methods. The statistical distribution shows no evidence of (anti)correlation between the speed and the length of the segments.
Lu Meng🇨🇳 · Ning Li🇩🇪 · Shi-Lin Zhu🇨🇳
We present a systematic investigation of the possible molecular states composed of a pair of doubly charmed baryons () or one doubly charmed baryon and one doubly charmed antibaryon within the framework of the one-boson-exchange-potential model. For the spin-triplet systems, we take into account the mixing between the and channels. For the baryon-baryon system with and , where and represent the group representation and the isospin of the system, respectively, there exist loosely bound molecular states. For the baryon-antibaryon system with , and , there also exist deuteron-like molecules. The molecular states may be produced at LHC. The proximity of their masses to the threshold of two doubly charmed baryons provides a clean clue to identify them.
The central part of this thesis deals with the quantum chromodynamics (QCD) radiative corrections to some important observables associated with the Drell-Yan, scalar and pseudo-scalar Higgs boson productions at next-to-next-to-next-to-leading order (NLO) aiming to uplift the accuracy of theoretical results. The Higgs bosons are produced dominantly at the Large Hadron Collider (LHC) via gluon fusion through top quark loop, while one of the subdominant ones takes place through bottom quark annihilation whose contribution is equally important and must be included in precision studies. Here, we have computed analytically the inclusive cross section of the Higgs boson produced through this channel under the soft-virtual (SV) approximation at NLO QCD following an elegant formalism. Moreover, the differential rapidity distribution is another most important observable, which is expected to be measured in upcoming days at the LHC. This immediately calls for very precise theoretical predictions. The analytical expressions of the SV corrections to this observable at NLO for the Higgs boson, produced through gluon fusion, and leptonic pair in Drell-Yan (DY) production are computed and the numerical impacts of these results are demonstrated. In addition, the CP-odd/pseudo-scalar Higgs boson, which is one of the most prime candidates in BSM scenarios, is studied in great details, taking into account the QCD radiative corrections. We have computed the analytical results of the three loop QCD corrections to the pseudo-scalar Higgs boson production and consequently, obtained the inclusive production cross section at NLO under SV approximation. These indeed help to reduce the theoretical uncertainties arising from the renormalisation and factorisation scales and undoubtedly, improve the reliabilities of the theoretical results.
Luca Marzola🇪🇪 · Antonio Racioppi🇪🇪 · Ville Vaskonen🇪🇪
Thermal corrections in classically conformal models typically induce a strong first-order electroweak phase transition, thereby resulting in a stochastic gravitational wave background that could be detectable at gravitational wave observatories. After reviewing the basics of classically conformal scenarios, in this paper we investigate the phase transition dynamics in a thermal environment and the related gravitational wave phenomenology within the framework of scalar conformal extensions of the Standard Model. We find that minimal extensions involving only one additional scalar field struggle to reproduce the correct phase transition dynamics once thermal corrections are accounted for. Next-to-minimal models, instead, yield the desired electroweak symmetry breaking and typically result in a very strong gravitational wave signal.
Shivaramakrishna Singirala🇮🇳 · Rukmani Mohanta🇮🇳 · Sudhanwa Patra🇮🇳
We investigate the phenomenology of singlet scalar dark matter in a simple gauge extension of the Standard Model where the dark matter particle is charged under the symmetry. The non-trivial gauge anomalies are cancelled with the introduction of three exotic fermions with charges as , instead of right-handed neutrinos with in conventional model. Without the need of any ad-hoc discrete symmetry, the charge plays a crucial role in stabilizing the dark matter. We make a comprehensive study of dark matter phenomenology in the scalar and gauge portals separately. In the gauge-mediated regime, we invoke the LEP-II constraints and dilepton limits of ATLAS on the gauge parameters. A massless physical Goldstone plays a vital role in the scalar-portal dark matter observables, becomes a unique feature of the model. We show the mechanism of generating the light neutrino mass at one-loop level where the dark matter singlet runs in the loop. We shed light on the semi-annihilation and finally, we comment on indirect signals in this framework.
Luca Di Luzio🇬🇧 · Enrico Nardi🇮🇹 · Lorenzo Ubaldi🇮🇱
A gauge theory for a scalar multiplet transforming in the bi-fundamental representation preserves, for , an accidental symmetry firstly broken at operator dimension . Two configurations are possible for the vacuum expectation value of , which correspond to the (maximal) little groups and . In the first case the accidental gets also broken, yielding a pseudo Nambu-Goldstone boson with mass suppression controlled by , while in the second case a global remains unbroken. The strong CP problem is solved by coupling to new fermions carrying color. The first case allows for a Peccei-Quinn solution with protected up to order by the gauge symmetry. In the second case can get broken by condensates of the new strong dynamics, resulting in a composite axion. By coupling to fermions carrying only weak isospin, models for axion-like particles can be constructed.
Mahdi Eshgh🇮🇷 · Hussain Mehraban🇮🇷 · Sameer M. Ikhdair🇵🇸
We investigate the relativistic effects of a moving particle in the field of a pseudo-harmonic oscillatory ring-shaped potential under the spin and pseudo-spin symmetric Dirac wave equation. We obtain the bound state energy eigenvalue equation and the corresponding two-components spinor wave functions by using the formalism of Suppersymmetric Quantum Mechanics (SUSYQM). Furthermore, the non-relativistic limits are obtained by simply making a proper replacement of parameters. The thermodynamic properties are shortly studied. Our numerical results for the energy eigenvalues are presented too.
Mahdi Eshghi🇮🇷 · Hussain Mehraban🇮🇷 · Sameer M. Ikhdair🇵🇸
We present a more general form of the Schrödinger equation in curvilinear space that is exposed to external fields. Thereby, we solve the wave equation with the Cornell plus harmonic potentials (CHP) under the influence of the magnetic and Aharonov-Bohm (AB) flux fields using curvilinear coordinates system in such space. With this requirement, the energy spectrum and the corresponding wave functions are calculated by means of the series method. The mass spectrum of both charmonium and bottomonium states consisting of quark and antiquark are calculated. In addition, the main thermodynamic functions such as the free energy, the mean energy, the entropy, the specific heat, the persistent currents and magnetization are obtained by using the characteristic function. We draw the resulting energy states and the thermodynamic quantities versus some potential parameters, magnetic field and temperature to see their numerical behaviors. Finally, we give some discussions to our results.
We study the emission of soft photons coupling to high energy fixed angle scattering processes at first order in the electromagnetic coupling but to all loop orders in a class of theories without soft divergences, including massive and massless Yukawa and scalar theories. We adapt a method introduced by del Duca for quantum electrodynamics to show that subleading corrections to the soft photon theorem are sensitive to the structure of non leading external jets of collinear lines. Our techniques are based on a power counting analysis of loop integrals and an application of jet Ward identities. We also apply Grammer and Yennie's decomposition to isolate separately gauge invariant contributions to the soft photon expansion. These are interpreted as infrared sensitive matrix elements coupling to a field strength tensor.
Stephon Alexander🇺🇸 · Evan McDonough🇨🇦 · Robert Sims🇺🇸
We study the production of primordial circular ("V-mode") polarization in axion inflation coupled to fermions and gauge fields, with special attention paid to (p)reheating. We construct the power spectrum of , and find a blue-tilted spectrum with index . This is independent of the dominant decay channel of the inflaton (direct fermion vs. direct photon production)
Evan Berkowitz🇩🇪 · David Brantley🇺🇸 · Chris Bouchard🇬🇧 · Chia Cheng Chang🇺🇸 · M. A. Clark🇺🇸 · Nicholas Garron🇬🇧 · Balint Joo🇺🇸 · Thorsten Kurth🇺🇸 · Chris Monahan🇺🇸 · Henry Monge-Camacho🇺🇸 · Amy Nicholson🇺🇸 · Kostas Orginos🇺🇸 and 3 other authors
We report on a lattice QCD calculation of the nucleon axial charge, , using Möbius Domain-Wall fermions solved on the dynamical HISQ ensembles after they are smeared using the gradient-flow algorithm. The calculation is performed with three pion masses, MeV. Three lattice spacings ( fm) are used with the heaviest pion mass, while the coarsest two spacings are used on the middle pion mass and only the coarsest spacing is used with the near physical pion mass. On the MeV, fm point, a dedicated volume study is performed with . Using a new strategy motivated by the Feynman-Hellmann Theorem, we achieve a precise determination of with relatively low statistics, and demonstrable control over the excited state, continuum, infinite volume and chiral extrapolation systematic uncertainties, the latter of which remains the dominant uncertainty. Our final determination at 2.6\% total uncertainty is , with the first uncertainty including statistical and systematic uncertainties from fitting and the second including model selection systematics related to the chiral and continuum extrapolation. The largest reduction of the second uncertainty will come from a greater number of pion mass points as well as more precise lattice QCD results near the physical pion mass.
George M. Fuller🇺🇸 · Alexander Kusenko🇯🇵 · Volodymyr Takhistov🇺🇸
We show that some or all of the inventory of -process nucleosynthesis can be produced in interactions of primordial black holes (PBHs) with neutron stars (NSs) if PBHs with masses make up a few percent or more of the dark matter. A PBH captured by a neutron star (NS) sinks to the center of the NS and consumes it from the inside. When this occurs in a rotating millisecond-period NS, the resulting spin-up ejects of relatively cold neutron-rich material. This ejection process and the accompanying decompression and decay of nuclear matter can produce electromagnetic transients, such as a kilonova-type afterglow and fast radio bursts. These transients are not accompanied by significant gravitational radiation or neutrinos, allowing such events to be differentiated from compact object mergers occurring within the distance sensitivity limits of gravitational wave observatories. The PBH-NS destruction scenario is consistent with pulsar and NS statistics, the dark matter content and spatial distributions in the Galaxy and Ultra Faint Dwarfs (UFD), as well as with the -process content and evolution histories in these sites. Ejected matter is heated by beta decay, which leads to emission of positrons in an amount consistent with the observed 511-keV line from the Galactic Center.
* 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.