New articles on High Energy Physics - Phenomenology


[1] 2205.06272

Supernova Fast Flavor Conversions in 1+1 D : Influence of Mu-tau neutrinos

In the dense supernova environment, neutrinos can undergo fast flavor conversions which depend on the large neutrino-neutrino interaction strength. It has been recently shown that both their presence and outcome can be affected when passing from the commonly used three neutrino species approach to the more general with six species. Here we build up on a previous work performed on this topic and, for the first time, perform a numerical simulation of flavor evolution in both space and time, assuming six neutrino species. We find that the results presented in our previous work remain qualitatively the same even for flavor evolution in space and time. This emphasizes the need for going beyond the simplistic approximation with three species when studying fast flavor conversions.


[2] 2205.06295

More Doublets and Singlets

I give an overview on models that extend the Standard Model scalar sector by additional gauge singlets or multiplets. I discuss current constraints on such models, as well as possible signatures and discovery prospects at current and future colliders.


[3] 2205.06332

Effects of Lorentz violation in the Higgs sector of the Minimal Standard Model Extension

A bound on the CPT-odd four vector coefficient $k^\mu_\phi$ that appears in Higgs sector of the Minimal Standard Model Extended (MSME) is presented. The analysis is based on the contributions arising from the sector in question to the anomalous dipole moment for leptons calculated at the one loop level, for which an analytical expression is obtained. The largest contribution of this Lorentz violating coefficient is on the lightest lepton, which results as a consequence of a strong non-decoupling effect. By using the experimental uncertainty of the electron anomalous dipole moment we predict that $|k^2_{ \phi\,R}|<3.29\times 10^{-29}$ GeV$^2$.


[4] 2205.06339

Master integrals for ${\cal O}(αα_s)$ corrections to $H \to ZZ^*$

We present analytic results for all the Feynman integrals relevant for ${\mathcal O}(\alpha \alpha_s)$ virtual corrections to $H \rightarrow ZZ^*$ decay. We use the method of differential equations to solve the master integrals while keeping the full dependence on the masses of all the particles including internal propagators. Due to the presence of four mass scales we encounter multiple square roots. We argue that all the occurring square roots can not be rationalized at the same time as a simultaneous rationalization brings us to integrals over $CY_3$ manifolds. Hence we rationalize only three square roots simultaneously and construct suitable ans\"atze to obtain dlog-forms containing the square root, after obtaining an epsilon-factorised form for the differential equations. We present the alphabet and the analytic form of all the boundary constants that appear in the solutions of the differential equations. The results for master integrals are expressed in terms of Chen's iterated integrals with dlog one-forms.


[5] 2205.06378

ACHILLES: A novel event generator for electron- and neutrino-nucleus scattering

We present a novel lepton-nucleus event generator: ACHILLES, A CHIcagoLand Lepton Event Simulator. The generator factorizes the primary interaction from the propagation of hadrons in the nucleus, which allows for a great deal of modularity, facilitating further improvements and interfaces with existing codes. We validate our generator against high quality electron-carbon scattering data in the quasielastic regime, including the recent CLAS/e4v reanalysis of existing data. We find good agreement in both inclusive and exclusive distributions. By varying the assumptions on the propagation of knocked out nucleons throughout the nucleus, we estimate a component of theoretical uncertainties. We also propose novel observables that will allow for further testing of lepton-nucleus scattering models. ACHILLES is readily extendable to generate neutrino-nucleus scattering events.


[6] 2205.06411

In-medium polarization tensor in strong magnetic fields (II): Axial Ward identity at finite temperature and density

We investigate the axial Ward identity (AWI) for massive fermions in strong magnetic fields. The divergence of the axial-vector current is computed at finite temperature and/or density with the help of a relation between the polarization and anomaly diagrams in the effective (1+1) dimensions realized in the lowest Landau level (LLL). We discuss delicate interplay between the vacuum and medium contributions that determines patterns of the spectral flow in the adiabatic limit and, more generally, the diabatic chirality production rate. We also establish an explicit relation between the AWIs from the LLL approximation and from the familiar triangle diagrams in the naive perturbative series with respect to the coupling constant.


[7] 2205.06431

Recent dark matter results from the GAMBIT collaboration

In this proceeding, I present the results of a recent global fit of an effective field theory of dark matter, performed using the Global and Modular Beyond-the-Standard Model Inference Tool (GAMBIT). A Dirac fermion dark matter candidate is assumed to interact only with Standard Model quarks and gluons, through a general set of operators up to mass dimension 7. The results provide a reasonably up-to-date summary of our knowledge of possible WIMP interactions.


[8] 2205.06545

On Minimal realization of Topological Lorentz Structures with one-loop Seesaw extensions in A$_4$ Modular Symmetry

Topological classification of one-loop Weinberg operator leads to systematic categorization of one-loop neutrino mass models. All one-loop neutrino mass models must fall in one of these categories. Among these topological categories, loop extension of canonical seesaw scenarios is interesting in light of the current LHC run. Apart from one-loop contribution, these extensions result in dominant tree-level contribution to neutrino masses. In order to have dominant one-loop contribution, one requires suppression of tree-level contribution which cannot be accomplished using the cyclic, continuous or discrete flavor symmetries alone. The immediate remedy to obtain dominant one-loop contribution requires combination of flavor symmetries and enlarged field content. Alternatively, in this work, we propose a minimal way of realizing the topological structures with dominant one-loop contribution using modular variant of the permutation symmetries. In such a realization, no new fields are needed apart from those permitted by the topology itself. We have realized one such topological Lorentz structure(T4-2-$i$) pertaining to one-loop extension of Type-II seesaw using modular A$_4$ symmetry. Here, modular weights play an important role in suppressing tree-level terms and stabilizing the particles running in the loop($N_i$, $\rho$ and $\phi$), thus, making them suitable dark matter candidates. In fact, the model accommodates possibility of scalar or fermionic dark matter candidate depending on whichever is lightest. We have, also, analyzed the viability of the model under neutrino oscillation data and obtained model predictions for effective Majorana mass $M_{ee}$ and $CP$ violation.


[9] 2205.06642

Coherent pion production in neutrino (anti-neutrino)-nucleus interaction

We present a study of coherent pion production in neutrino-nucleus interactions using the formalism based on partially conserved axial current theorem which connects the neutrino-nucleus cross section to the pion-nucleus elastic scattering cross section. Pion-nucleus elastic scattering cross section is calculated using Glauber model which takes three inputs, nuclear densities, pion-nucleon cross section and $\alpha_{\pi N}$ which is the ratio of real to imaginary part of $\pi N$ forward scattering amplitude, for which the parametrizations are obtained from measured data. We calculate the differential and integrated cross sections for charge and neutral current coherent pion production in neutrino (anti-neutrino)-nucleus scattering for a range of nuclear targets from light to heavy materials such as lithium, carbon, hydrocarbon, oxygen, silicon, argon, iron and lead. The results of these cross section calculations are compared with the measured data and with the calculations from the Berger-Sehgal model and GENIE package. There is an excellent agreement between the calculated and measured cross sections with Glauber model. While GENIE and Berger-Sehgal model give a good description of the data in the lower energy range the present calculations describe the data in all energy ranges. Predictions are also made for upcoming experiments like INO and DUNE in the coherent region of neutrino cross section.


[10] 2205.06646

Safe $Z'$ for LFUV

It is demonstrated that accounting for lepton flavor universality violating anomalies in $B$ meson decays via $Z'$ models implies a Landau pole problem. A family of models is proposed that resolve both issues simultaneously, fix the metastability of the Higgs and are predictive up to the Planck scale.


[11] 2205.06669

Multi-step phase transitions and gravitational waves in the inert doublet model

The inert doublet model is a well-motivated extension of the Standard Model that contains a dark matter candidate and modifies the dynamics of the electroweak symmetry breaking. In order to detail its phenomenology, we perform a comprehensive study of cosmic phase transitions and gravitational wave signals implied by the framework, accounting for the latest results of collider experiments. We require the neutral inert scalar to constitute, at least, a subdominant part of the observed dark matter abundance. While most of the phase transitions proceed through a single step, we identify regions of the parameter space where the electroweak vacuum is reached after multiple phase transitions. The resulting gravitational wave spectrum is generally dominated by single-step transitions and, in part of the parameter space, falls within the reach of near-future gravitational wave detectors such as LISA or BBO. We find that direct detection experiments efficiently probe the part of parameter space associated with multi-step phase transitions, which remain unconstrained only in the Higgs resonance region testable with future monojet searches. The implications of the new determination of the $W$ boson mass are also discussed.


[12] 2205.06712

Coherent elastic neutrino-nucleus scattering -- First constraints/observations and future potential

The detection of coherent elastic neutrino-nucleus scattering (CE$\nu$NS) opens new possibilities for neutrino physics within and beyond the Standard Model. Following the initial discovery in 2017, several experimental attempts have emerged allowing this reaction channel to be studied with the full repertoire of modern detection technologies. As one of several reactor experiments, CONUS aims for an observation with antineutrinos emitted from the powerful $3.9$ GW$_{th}$ reactor of the nuclear power plant in Brokdorf (Germany). In particular, the application of ultra-low threshold, high-purity germanium detectors within a sophisticated shield design in close proximity to a nuclear reactor core represents an important step towards high-statistics neutrino detection with small-scale detectors. In addition to the conventional interaction, typical extensions of the Standard Model neutrino sector can be investigated with data provided from different neutrino sources and several target materials. Among these, new neutrino interactions as well as electromagnetic neutrino properties are of particular interest. This talk gives an overview of existing CE$\nu$NS results and highlights the advantage of using different neutrino sources and target materials. The example of CONUS is used to demonstrate the various capabilities of recent and future CE$\nu$NS measurements.


[13] 2205.06724

Spatial entanglement in two dimensional QCD: Renyi and Ryu-Takayanagi entropies

We derive a general formula for the replica partition function in the vacuum state, for a large class of interacting theories with fermions, with or without gauge fields, using the equal-time formulation on the light front. The result is used to analyze the spatial entanglement of interacting Dirac fermions in two-dimensional QCD. A particular attention is paid to the issues of infrared cut-off dependence and gauge invariance. The Renyi entropy for a single interval, is given by the rainbow dressed quark propagator to order ${\cal O}(N_c)$. The contributions to order ${\cal O}(1)$, are shown to follow from the off-diagonal and off mass-shell mesonic T-matrix, with no contribution to the central charge. The construction is then extended to mesonic states on the light front, and shown to probe the moments of the partonic PDFs for large light-front separations. In the vacuum and for small and large intervals, the spatial entanglement entropy following from the Renyi entropy, is shown to be in agreement with the Ryu-Takayanagi geometrical entropy, using a soft-wall AdS$_3$ model of two-dimensional QCD.


[14] 2205.06726

Diagram of High Energy Nuclear Collisions

Many new particles, mostly hadrons, are produced in high energy collisions between atomic nuclei. The most popular models describing the hadron production process are based on the creation, evolution and decay of resonances, strings or quark-gluon plasma. The validity of these models is under vivid discussion, and it seems that a common framework for this discussion is missing. Here we introduce the diagram of high energy nuclear collisions, where domains of the dominance of different hadron-production processes in the space of laboratory-controlled parameters, the collision energy and nuclear-mass number of colliding nuclei, are indicated. We argue, the recent experimental results locate boundaries between the domains, allowing for the first time to sketch an example diagram. Finally, we discuss the immediate implications for experimental measurements and model development following the sketch.


[15] 2205.06746

Dispersive derivation of the pion distribution amplitude

We derive the dependence of the leading-twist pion light-cone distribution amplitude (LCDA) on a parton momentum fraction $x$ by directly solving the dispersion relations for the moments with inputs from the operator product expansion (OPE) of the corresponding correlation function. It is noticed that these dispersion relations must be organized into those for the Gegenbauer coefficients first in order to avoid the ill-posed problem appearing in the conversion from the moments to the Gegenbauer coefficients. Given the values of various condensates in the OPE, we find that a solution for the pion LCDA, which is stable in the Gegenbauer expansion, exists. Moreover, the solution from summing contributions up to 18 Gegenbauer polynomials is smooth, and can be well approximated by a function proportional to $x^p(1-x)^p$ with $p\approx 0.45$ at the scale $\mu=2$ GeV. Turning off the condensates, we get the asymptotic form, independent of the scale $\mu$, for the pion LCDA as expected. We then solve for the pion LCDA at a different scale $\mu=1.5$ GeV with the condensate inputs at this $\mu$, and demonstrate that the result is consistent with the one obtained by evolving the Gegenbauer coefficients from $\mu=2$ GeV to 1.5 GeV. That is, our formalism is compatible with the QCD evolution. The strength of the above approach that goes beyond analyses limited to only the first few moments of a LCDA in conventional QCD sum rules is highlighted. The precision of our results can be improved systematically by including higher-order and higher-power terms in the OPE.


[16] 2205.06270

An Effective Bias Expansion for 21 cm Cosmology in Redshift Space

A near-future detection of the 21cm signal from the epoch of reionization will provide unique opportunities to probe the underlying cosmology, provided that such cosmological information can be extracted with precision. To this end, we further develop effective field theory (EFT) inspired techniques for the 21cm brightness temperature field during the epoch of reionization, incorporating renormalized bias and a treatment of redshift space distortions. Notably, we confirm that in redshift space, measures of the 21cm brightness, e.g the power spectrum, should have irreducible contributions that lack a bias coefficient and therefore contain direct, astrophysics-free information about the cosmological density field; in this work, we study this effect beyond linear order. To validate our theoretical treatment, we fit the predicted EFT Fourier-space shapes to the THESAN suite of hydrodynamical simulations of reionization at the field level, where the considerable number of modes prevents overfitting. We find agreement at the level of a few percent between the 21cm power spectrum from the EFT fits and simulations over the wavenumber range $k \lesssim 0.8$ h/Mpc and neutral fraction $x_\mathrm{HI} \gtrsim 0.4$, which is imminently measurable by the Hydrogen Epoch of Reionization Array (HERA) and future experiments. The ability of the EFT to describe the 21cm signal extends to simulations that have different astrophysical prescriptions for reionization as well as simulations with interacting dark matter.


[17] 2205.06273

From Rotating to Charged Black Holes and Back Again

The mild form of the Weak Gravity Conjecture (WGC) requires higher derivative corrections to extremal charged black holes to increase their charge-to-mass ratio. This allows decay via emission of a smaller extremal black hole. In this paper, we investigate if similar constraints hold for extremal rotating black holes. We do so by considering the leading higher derivative corrections to the four-dimensional Kerr black hole and five-dimensional Myers-Perry black hole. We use a known mapping of these rotating solutions to a four-dimensional non-rotating dyonic Kaluza-Klein black hole and impose the WGC on this charged solution. Going back again to the rotating solutions, this fixes the sign of the corrections to the rotating extremality bounds. The sign of the corrections is non-universal, depending on the black hole under consideration. We argue that this is not at odds with black hole decay, because of the presence of a superradiant instability that persists in the extremal limit. When this instability is present, the WGC is implied for the four-dimensional charged black hole.


[18] 2205.06274

A perfect fluid hydrodynamic picture of domain wall velocities at strong coupling

We show that for a range of strongly coupled theories with a first order phase transition, the domain wall or bubble velocity can be expressed in a simple way in terms of a perfect fluid hydrodynamic formula, and thus in terms of the equation of state. We test the predictions for the domain wall velocities using the gauge/gravity duality.


[19] 2205.06377

Dibaryon resonances and short-range $NN$ interaction

The dibaryon concept for the nuclear force is considered, assuming that the main attraction between the nucleons at medium distances is determined by the $s$-channel exchange of an intermediate six-quark (dibaryon) state. To construct the respective $NN$ interaction model, a microscopic six-quark description of the $NN$ system is used, in which symmetry aspects play a special role. The interaction within the dibaryon model includes a superposition of $t$-channel long-range one-pion exchange and $s$-channel dibaryon exchange. This interaction model is shown to give a good description of both elastic phase shifts and inelasticities of $NN$ scattering in various partial waves in a broad energy range from zero to 600-800 MeV and even higher. It is shown also that the suggested coupling between the external $NN$ channel and internal $6q$ channel leads to a dressing of the intermediate dibaryon state. Finally, the parameters of the dressed dibaryons corresponding to the best fit of $NN$ scattering data turn out to be very close to the parameters of the observed dibaryon resonances in those $NN$ partial configurations where their existence has been experimentally confirmed.


[20] 2205.06475

Inflation and primordial gravitational waves in scale-invariant quadratic gravity

In scale-invariant models of fundamental physics all mass scales are generated via spontaneous symmetry breaking. In this work, we study inflation in scale-invariant quadratic gravity, in which the Planck mass is generated classically by a scalar field, which evolves from an unstable fixed point to a stable one thus breaking scale-invariance. We investigate the dynamics by means of dynamical system standard techniques. By computing the spectral indices and comparing them with data, we put some constraints on the three dimensionless parameters of the theory. We show that certain regions of the parameter space will be within the range of future CMB missions like CMB-S4, LiteBIRD and STPol. The second half of the paper is dedicated to the analysis of inflationary first-order tensor perturbations and the calculation of the power spectrum of the gravitational waves. We comment on our results and compare them with the ones of mixed Starobinsky-Higgs inflation.


[21] 2205.06585

Double Hawking temperature: from black hole to de Sitter

The double Hawking temperature $T=2T_H$ appears in some approaches to the Hawking radiation, when the radiation is considered in terms of the quantum tunneling. We consider the origin of such temperature for the black hole horizon and also for the cosmological horizon in de Sitter spacetime. In case the black hole horizon, there are two contributions to the tunneling process of radiation, each being governed by the temperature $T=2T_H$. These processes are coherently combined to produce the radiation with the Hawking temperature $T_H$. This can be traditionally interpreted as the pair creation of two entangled particles, of which one goes towards the centre of the black hole, while the other one escapes from the black hole. In case of the cosmological horizon, the temperature $T=2T_H$ is physical. While the creation of the entangled pair is described by the Hawking temperature, the de Sitter spacetime allows for the another process, in which only single (non-entangled) particle inside the cosmological horizon is created. This process is characterized by the local temperature $T=2T_H$. Such single particle process is suppressed in case of the black hole horizon.


[22] 2205.06591

Notes on the experimental observation of the Unruh effect

The incorporation of classical general relativity into quantum field theory yields a surprising result -- thermodynamic particle production. One such phenomenon, known as the Unruh effect, causes empty space to effervesce a thermal bath of particles when viewed by an observer undergoing uniformly accelerated motion. These systems will have a Rindler horizon which produces this Unruh radiation at the Fulling-Davies-Unruh temperature. For accelerated charges, the emission and absorption of this radiation will imprint the FDU temperature on photons emitted in the laboratory. Each of these photons will also change the Rindler horizon in accordance with the Bekenstein-Hawking area-entropy law. In this essay, we will discuss these aspects of acceleration-induced thermality which have been experimentally observed in a high energy channeling experiment carried out by CERN-NA63.


[23] 2205.06707

Background Effective Action with Nonlinear Massive Gauge Fixing

We combine a recent construction of a BRST-invariant, nonlinear massive gauge fixing with the background field formalism. The resulting generating functional preserves background-field invariance as well as BRST invariance of the quantum field manifestly. The construction features BRST-invariant mass parameters for the quantum gauge and ghost fields. The formalism employs a background Nakanishi-Lautrup field which is part of the nonlinear gauge-fixing sector and thus should not affect observables. We verify this expectation by computing the one-loop effective action and the corresponding beta function of the gauge coupling as an example. The corresponding Schwinger functional generating connected correlation functions acquires additional one-particle reducible terms that vanish on shell. We also study off-shell one-loop contributions in order to explore the consequences of a nonlinear gauge fixing scheme involving a background Nakanishi-Lautrup field. As an application, we show that our formalism straightforwardly accommodates nonperturbative information about propagators in the Landau gauge in the form of the so-called decoupling solution. Using this nonperturbative input, we find evidence for the formation of a gluon condensate for sufficiently large coupling, whose scale is set by the BRST-invariant gluon mass parameter.