Wed·Feb 14, 2024Wednesday·February 14, 2024

1. 01*

   Neutrinoless double beta decay rates in the presence of light sterile neutrinos

   W. Dekens🇺🇸 · J. de Vries🇳🇱 · D. Castillo🇪🇸 · J. Menéndez🇪🇸 · E. Mereghetti🇺🇸 · V. Plakkot🇳🇱 · P. Soriano🇪🇸 · G. Zhou🇳🇱

   We investigate neutrinoless double-beta decay ($0\nu \beta \beta$) in minimal extensions of the Standard Model of particle physics where gauge-singlet right-handed neutrinos give rise to Dirac and Majorana neutrino mass terms. We argue that the standard treatment of these scenarios, based on mass-dependent nuclear matrix elements, is missing important contributions to the $0\nu \beta \beta$ amplitude. First, new effects arise from the exchange of neutrinos with very small (ultrasoft) momenta, for which we compute the associated nuclear matrix elements for the decays of ${}^{76}$Ge and ${}^{136}$Xe. These contributions can dominate the $0\nu \beta \beta$ rate in cases with light sterile neutrinos. The ultrasoft terms are also relevant in the more standard scenario of just three light Majorana neutrinos where they lead to a $10\%$ reduction of the total $0\nu \beta \beta$ amplitude. Secondly, we highlight the importance of short-range terms associated with medium-heavy sterile neutrinos and provide explicit formulae that can be used in phenomenological analyses. As examples we discuss impact of these new effects in several explicit scenarios, including a realistic $3+2$ model with two right-handed gauge-singlet neutrinos.

   hep-phnucl-thJHEP(2024)·32 citations
2. 02*

   Improvement and generalization of ABCD method with Bayesian inference

   Ezequiel Alvarez🇦🇷 · Leandro Da Rold🇦🇷 · Manuel Szewc🇺🇸 · Alejandro Szynkman🇦🇷 · Santiago A. Tanco🇦🇷 · Tatiana Tarutina🇦🇷

   To find New Physics or to refine our knowledge of the Standard Model at the LHC is an enterprise that involves many factors. We focus on taking advantage of available information and pour our effort in re-thinking the usual data-driven ABCD method to improve it and to generalize it using Bayesian Machine Learning tools. We propose that a dataset consisting of a signal and many backgrounds is well described through a mixture model. Signal, backgrounds and their relative fractions in the sample can be well extracted by exploiting the prior knowledge and the dependence between the different observables at the event-by-event level with Bayesian tools. We show how, in contrast to the ABCD method, one can take advantage of understanding some properties of the different backgrounds and of having more than two independent observables to measure in each event. In addition, instead of regions defined through hard cuts, the Bayesian framework uses the information of continuous distribution to obtain soft-assignments of the events which are statistically more robust. To compare both methods we use a toy problem inspired by $pp\to hh\to b\bar{b}b\bar{b}$, selecting a reduced and simplified number of processes and analysing the flavor of the four jets and the invariant mass of the jet-pairs, modeled with simplified distributions. Taking advantage of all this information, and starting from a combination of biased and agnostic priors, leads us to a very good posterior once we use the Bayesian framework to exploit the data and the mutual information of the observables at the event-by-event level. We show how, in this simplified model, the Bayesian framework outperforms the ABCD method sensitivity in obtaining the signal fraction in scenarios with $1\%$ and $0.5\%$ true signal fractions in the dataset. We also show that the method is robust against the absence of signal.

   hep-phcs.LGhep-exSciPost Phys.Core(2024)·8 citations
3. 03*

   Idealised Antenna Functions for Higher Order QCD Calculations

   Oscar Braun-White🇬🇧

   In this thesis, the infrared structure of squared matrix elements in quantum chromodynamics (QCD) is scrutinised. Specifically, the triple-collinear splitting functions are decomposed and improvements to antenna subtraction are sought through the construction of idealised antenna functions. The antenna-subtraction technique has demonstrated remarkable effectiveness in handling next-to-next-to-leading order (NNLO) infrared divergences for a wide range of QCD processes relevant for colliders. However, since antenna functions were historically extracted from matrix elements, they did not have uniform properties, which made the generation of subtraction terms complex. Antenna subtraction up to NNLO is reviewed, including the role of antenna functions. A general algorithm is detailed in order to re-build antenna functions, with idealised features, directly from a specified list of unresolved limits, for any number of real and virtual emissions. Using this general algorithm, together with the decomposition of the triple-collinear splitting functions, all the antenna functions required for NNLO QCD calculations in the final-final configuration are constructed and it is demonstrated that they form a consistent NNLO subtraction scheme. The idealised antenna functions should simplify the generation of subtraction terms and minimise the introduction of spurious limits. Additionally, the general algorithm sets out an initial blueprint for next-to-NNLO (N${}^3$LO) idealised antennae for use in N${}^3$LO QCD calculations.

   hep-ph1 citation
4. 04*

   The SM expected branching ratio for $h\to \gamma \gamma$ and an excess for $h\to Z\gamma$

   Xiao-Gang He🇨🇳 · Zhong-Lv Huang🇨🇳 · Ming-Wei Li🇨🇳 · Chia-Wei Liu🇨🇳

   The recent measurements of $h\to Z\gamma$ from ATLAS and CMS show an excess of the signal strength ${\mu }_Z=(\sigma \cdot \mathcal{B}{)}_{\mathrm{obs}}/(\sigma \cdot \mathcal{B}{)}_{\mathrm{SM}}=2.2\pm 0.7$, normalized as 1 in the standard model~(SM). If confirmed, it would be a signal of new physics (NP) beyond the SM. We study NP explanation for this excess. In general, for a given model, it also affects the process $h\to \gamma \gamma$. Since the measured branching ratio for this process agrees well with the SM prediction, the model is severely constrained. We find that a minimally fermion singlets and doublet extended NP model can explain simultaneously the current data for $h\to Z\gamma$ and $h\to \gamma \gamma$. There are two solutions. Although both solutions enhance the amplitude of $h\to Z\gamma$ to the observed one, in one of the solutions the amplitude of $h\to \gamma \gamma$ flips sign to give the observ ed branching ratio. This seems to be a contrived solution although cannot be ruled out simply using branching ratio measurements alone. However, we find another solution that naturally enhances $h\to Z\gamma$ to the measured value, but keeps the amplitude of $h\to \gamma \gamma$ close to its SM prediction. We also comment on the phenomenology associated with these new fermions.

   hep-phhep-exJHEP(2024)·14 citations
5. 05*

   Constructing model-agnostic likelihoods, a method for the reinterpretation of particle physics results

   Lorenz Gärtner🇩🇪 · Nikolai Hartmann🇩🇪 · Lukas Heinrich🇩🇪 · Malin Horstmann🇩🇪 · Thomas Kuhr🇩🇪 · Méril Reboud🇩🇪 · Slavomira Stefkova🇩🇪 · Danny van Dyk🇬🇧

   Experimental High Energy Physics has entered an era of precision measurements. However, measurements of many of the accessible processes assume that the final states' underlying kinematic distribution is the same as the Standard Model prediction. This assumption introduces an implicit model-dependency into the measurement, rendering the reinterpretation of the experimental analysis complicated without reanalysing the underlying data. We present a novel reweighting method in order to perform reinterpretation of particle physics measurements. It makes use of reweighting the Standard Model templates according to kinematic signal distributions of alternative theoretical models, prior to performing the statistical analysis. The generality of this method allows us to perform statistical inference in the space of theoretical parameters, assuming different kinematic distributions, according to a beyond Standard Model prediction. We implement our method as an extension to the pyhf software and interface it with the EOS software, which allows us to perform flavor physics phenomenology studies. Furthermore, we argue that, beyond the pyhf or HistFactory likelihood specification, only minimal information is necessary to make a likelihood model-agnostic and hence easily reinterpretable. We showcase that publishing such likelihoods is crucial for a full exploitation of experimental results.

   hep-phhep-exEPJC(2024)·20 citations
6. 06*

   Multiplicity dependence of the freezeout parameters in high energy hadron-hadron collisions

   Muhammad Ajaz🇵🇰 · Majid Shehzad🇵🇰 · Muhammad Waqas🇨🇳 · Haifa I. Alrebdi🇸🇦 · Momhammad Ayaz Ahmad🇳🇴 · Antalov Jagnandan🇳🇴 · Shawn Jagnandan🇳🇴 · Murad Badshah🇵🇰 · Jalal Hasan Baker🇸🇦 · Abdul Mosawir Quraishi🇸🇦

   We examined the transverse momentum spectra of various identified particles, across different multiplicity classes in proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 7 TeV. Utilizing the Tsallis and Hagedorn models, parameters relevant to the bulk properties of nuclear matter were extracted. Both models exhibit good agreement with experimental data. In our analyses, we observed a consistent decrease in the effective temperature for the Tsallis model and the kinetic or thermal freeze-out temperature for the Hagedorn model, as we transition from higher multiplicity (class-I) to lower multiplicity (class-X). Additionally, the transverse flow velocity experiences a decline from class-I to class-X. The normalization constant which represents the multiplicity of produced particles is observed to decrease as we move towards higher multiplicity classes. While the effective and kinetic freeze-out temperatures, as well as the transverse flow velocity, show a mild dependency on multiplicity for lighter particles, this relationship becomes more pronounced for heavier particles. Various particle species are observed to undergo decoupling from the fireball at distinct temperatures: lighter particles exhibit lower temperatures, while heavier ones show higher temperatures, thereby supporting the concept of multiple freeze-out scenarios. Moreover, we identified a positive correlation between the kinetic freeze-out temperature and transverse flow velocity, a scenario where particles experience stronger collective motion at higher freeze-out temperature. The reason for this positive correlation is that as the multiplicity increases, more energy is transferred into the system. This heightened energy causes greater excitation and pressure within the system, leading to a quick expansion.

   hep-phCPC(2024)·11 citations
7. 07*

   Constraints on Variation of the Weak Scale from Big Bang Nucleosynthesis

   Anne-Katherine Burns🇺🇸 · Venus Keus🇮🇪 · Marc Sher🇺🇸 · Tim M.P. Tait🇺🇸

   Recently, the EMPRESS collaboration has included new data in the extraction of the primordial ${}^4$He abundance from Big Bang Nucleosynthesis (BBN), resulting in a determination that differs from the previous value and from theoretical expectations. There have been several studies attempting to explain this anomaly which involve variation of fundamental constants between the time of BBN and the present. Since the Higgs vacuum expectation value (vev) is the only dimensionful parameter in the Standard Model and it is already known to vary during the electroweak phase transition, we consider the possibility that the vev is slightly different during BBN compared to its present value. A modification of the vev changes not only particle masses but also affects, through mass thresholds, the QCD confinement scale. We use the recently developed PRyMordial program to study this variation and its impact on the ${}^4$He and deuterium abundances. We find that bounds on $|\delta v/v|$ are approximately $0.01$, and that the EMPRESS result can be explained within $2\sigma$ if $0.008<\delta v/v<0.02$, but at the cost of worsening the current $2\sigma$ discrepancy in the deuterium abundance to over $3\sigma$.

   hep-phastro-ph.HEnucl-thPRD(2024)·14 citations
8. 08*

   Dark matter as the trigger of flavor changing neutral current decays of the top quark

   Adil Jueid🇰🇷 · Shinya Kanemura🇯🇵

   We suggest a simplified model that simultaneously addresses the dark-matter problem and give rise to top quark flavor changing neutral current (FCNC) interactions at the one-loop order. The model consists of two extra $SU(2{)}_L$ gauge singlets: a colored mediator of spin zero ($S$) and a right-handed fermion ($\chi$) both are odd under an ad-hoc $Z_2$ symmetry. The right-handed fermion plays the role of the dark-matter candidate. In this model, the presence of the two dark sector particles generates one-loop induced FCNC decays of the top quark into light quarks and bosons such as the gluon, the photon, the $Z$-boson or the Higgs boson. As a case study, we analyze the top quark FCNC decays into light quarks ($u$ or $c$) and a $Z$ or Higgs bosons. We then study the reliable solutions to the dark-matter problem by estimating the regions in the parameter space that are consistent with the \textsc{Planck} measurement of the dark-matter relic density. We also revisit the bounds from the searches of dark matter in events with at least one high-$p_T$ jet and large missing transverse energy at the Large Hadron Collider (LHC). We then define four benchmark points that are consistent with the existing constraints from collider experiments and cosmology. We finally estimate, for these benchmark scenarios, the rates of a broad range of channels that can be used to probe the connection between the top FCNC transitions and dark matter both at the HL-LHC and a future $100$ TeV collider.

   hep-phPRD(2024)·10 citations
9. 09*

   Field Redefinitions and Infinite Field Anomalous Dimensions

   Aneesh V. Manohar🇺🇸 · Julie Pagès🇺🇸 · Jasper Roosmale Nepveu🇩🇪

   Field redefinitions are commonly used to reduce the number of operators in the Lagrangian by removing redundant operators and transforming to a minimal operator basis. We give a general argument that such field redefinitions, while leaving the $S$-matrix invariant and consequently finite, lead not only to infinite Green's functions, but also to infinite field anomalous dimensions ${\gamma }_{\varphi }$. These divergences cannot be removed by counterterms without reintroducing redundant operators.

   hep-phhep-thJHEP(2024)·17 citations
10. 10*

    Axion dark matter from inflation-driven quantum phase transition

    Ameen Ismail🇺🇸 · Seung J. Lee🇰🇷 · Bingrong Yu🇺🇸

    We propose a new mechanism to produce axion dark matter from inflationary fluctuations. Quantum fluctuations during inflation are strengthened by a coupling of the axion kinetic term to the inflaton, which we parametrize as an effective curvature $\kappa$ in the axion equation of motion. A nonvanishing curvature breaks the scale invariance of the axion power spectrum, driving a quantum phase transition with $\kappa$ as the order parameter. The axion power spectrum is proportional to the inverse comoving horizon to the power of $\kappa$. For positive $\kappa$ the spectrum gets a red tilt, leading to an exponential enhancement of the axion abundance as the comoving horizon shrinks during inflation. This enhancement allows sufficient axion production to comprise the entire dark matter relic abundance despite the ultralight mass. Our mechanism predicts a significantly different parameter space from the usual misalignment mechanism. It allows for axion-like particle dark matter with a much lower decay constant and thus a larger coupling to Standard Model particles. Much of the parameter space can be probed by future experiments including haloscopes, nuclear clocks, CASPEr, and CMB-S4. We can also generate heavier QCD axion dark matter than the misalignment mechanism.

    hep-phastro-ph.COgr-qchep-ex+14 citations
11. 11*

    Constraining neutrino-DM interactions with Milky Way dwarf spheroidals and supernova neutrinos

    Sean Heston🇺🇸 · Shunsaku Horiuchi🇺🇸 · Satoshi Shirai🇯🇵

    We constrain the neutrino-dark matter cross section using properties of the dark matter density profiles of Milky Way dwarf spheroidal galaxies. The constraint arises from core-collapse supernova neutrinos scattering on dark matter as a form of energy injection, allowing the transformation of the dark matter density profile from a cusped profile to a flatter profile. We assume a standard cosmology of dark energy and cold, collisionless, and non-self-interacting dark matter. By requiring that the dark matter cores do not lose too much mass or overshoot constraints from stellar kinematics, we place an upper limit on the cross section of ${\sigma }_{\nu -\mathrm{DM}}(E_{\nu }=15\mathrm{MeV},m_{\chi }\lesssim 130\mathrm{GeV})\approx 3.4\times 10^{-23}\mathrm{c}{\mathrm{m}}^2$ and ${\sigma }_{\nu -\mathrm{DM}}(E_{\nu }=15\mathrm{MeV},m_{\chi }\gtrsim 130\mathrm{GeV})\approx 3.2\times 10^{-27}{\left(\frac{m_{\chi }}{1\mathrm{GeV}}\right)}^2\mathrm{c}{\mathrm{m}}^2$, which is stronger than previous bounds for these energies. Consideration of baryonic feedback or host galaxy effects on the dark matter profile can strengthen this constraint.

    hep-phastro-ph.GAastro-ph.HEPRD(2024)·24 citations
12. 12*

    Fuzzy Bounces

    Massimo Giovannini🇨🇭

    We observe that the energy and the enthalpy densities can be smeared by two fudge factors that are constrained by the contracted Bianchi identities. Depending on the analytic properties of the smearing functions the underlying cosmological solutions belong to two physically different classes, namely the bounces of the scale factor and the curvature bounces. While the curvature bounces are naturally compatible with a stage of accelerated expansion, the bounces of the scale factor demand an early phase of accelerated contraction even if a short inflationary stage may arise prior to the decelerated regime. Despite the regularity of the underlying solutions, gradient instabilities and singularities do occasionally appear in the evolution of curvature inhomogeneities. After deducing the specific criteria behind these occurrences, the background-independent conclusions are corroborated by a series of concrete examples associated with different forms of the smearing functions. The evolution of the curvature inhomogeneities restricts the ranges of the solutions that turn out to be unsuitable even for a limited description of the pre-inflationary initial data. The same observation holds in the case of the gauge-invariant evolution of the matter density contrast. It is however not excluded that a class of scenarios (mainly associated with the curvature bounces) could indeed avoid the potential instabilities. All in all the present analysis explore a general approach whose results are relevant in all the contexts where bouncing solutions are invoked either as complementary or as alternative to the conventional inflationary scenarios.

    ↳ gr-qcastro-ph.COhep-phhep-thClass.Quant.Grav.(2024)·2 citations
13. 13*

    Shadows of rotating hairy Kerr black holes coupled to time periodic scalar fields with non-flat target space

    Galin N. Gyulchev🇧🇬 · Ayush Roy🇬🇧 · Lucas G. Collodel🇩🇪 · Petya G. Nedkova🇧🇬 · Stoytcho S. Yazadjiev🇧🇬 · Daniela D. Doneva🇩🇪

    We study the shadows cast by rotating hairy black holes with two non-trivial time-periodic scalar fields having a non-flat Gaussian curvature of the target space spanned by the scalar fields. Such black holes are a viable alternative to the Kerr black hole, having a much more complicated geodesic structure and resulting shadows. We investigate how a nontrivial Gauss curvature alters the pictures for different amounts of scalar hair around the black holes, quantified by a normalized charge. Our results show that for high values of this charge, close to a boson star limit, chaotic shadows are observed with multiple small disconnected components for all considered Gaussian curvatures. For moderately large amounts of scalar hair and corresponding normalized charge, although the shadows still exhibit chaotic behavior, a dominant shadow component emerges, the size and shape of which are substantially influenced by the Gaussian curvature. For instance, highly chaotic shadows for flat target space, start developing a large central shadow region with the increase of the Gauss curvature even for black holes with substantially heavy scalar hair. For lower values of the normalized charge, the shadows resemble qualitatively the Kerr black hole while the Gaussian curvature has a small impact on their properties.

    ↳ gr-qchep-phPRD(2024)·10 citations
14. 14*

    Finite density QCD equation of state: critical point and lattice-based $T^{\prime }$-expansion

    Micheal Kahangirwe🇺🇸 · Steffen A. Bass🇺🇸 · Elena Bratkovskaya🇩🇪 · Johannes Jahan🇺🇸 · Pierre Moreau🇺🇸 · Paolo Parotto🇺🇸 · Damien Price🇺🇸 · Claudia Ratti🇺🇸 · Olga Soloveva🇩🇪 · Mikhail Stephanov🇺🇸

    We present a novel construction of the QCD equation of state (EoS) at finite baryon density. Our work combines a recently proposed resummation scheme for lattice QCD results with the universal critical behavior at the QCD critical point. This allows us to obtain a family of equations of state in the range $0\le {\mu }_B\le 700$ MeV and 25 MeV $\le T\le 800$ MeV, which match lattice QCD results near ${\mu }_B=0$ while featuring a critical point in the 3D Ising model universality class. The position of the critical point can be chosen within the range accessible to beam-energy scan heavy-ion collision experiments. The strength of the singularity and the shape of the critical region are parameterized using a standard parameter set. We impose stability and causality constraints and discuss the available ranges of critical point parameter choices, finding that they extend beyond earlier parametric QCD EoS proposals. We present thermodynamic observables, including baryon density, pressure, entropy density, energy density, baryon susceptibility and speed of sound, that cover a wide range in the QCD phase diagram relevant for experimental exploration.

    ↳ nucl-thhep-phPRD(2024)·38 citations

* 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.