Tue·Sep 5, 2023Tuesday·September 5, 2023

1. 01*

   Jet quenching in anisotropic flowing matter

   Matvey V. Kuzmin🇷🇺 · Xoán Mayo López🇪🇸 · Jared Reiten🇺🇸 · Andrey V. Sadofyev🇪🇸

   We study the interplay between the flow and hydrodynamic gradients in jet quenching at first order in opacity. We find that the mixed flow-gradient contributions in jet quenching are enhanced by the medium length, and survive in the eikonal limit, dominating over other medium evolution effects. The resulting modification to the jet quenching parameter and energy loss rate can be substantial, leading to ample phenomenological implications. We also compute the leading corrections to the jet broadening due to the flow velocity gradients, and consider the leading gradient effects in the medium-induced branching for general kinematics, extending the recent considerations of jets in inhomogeneous media. These results can be straightforwardly coupled to matter simulations, providing new opportunities for jet tomography in heavy-ion collisions.

   hep-phnucl-thPRD(2024)·43 citations
2. 02*

   Analytic three-loop QCD corrections to top-quark and semileptonic $b\to u$ decays

   Long-Bin Chen🇨🇳 · Hai Tao Li🇨🇳 · Zhao Li🇨🇳 · Jian Wang🇨🇳 · Yefan Wang🇨🇳 · Quan-feng Wu🇨🇳

   We present the first analytic results of N${}^3$LO QCD corrections to the top-quark decay width. We focus on the dominant leading color contribution, which includes light-quark loops. At NNLO, this dominant contribution accounts for 95% of the total correction. By utilizing the optical theorem, the N${}^3$LO corrections are related to the imaginary parts of the four-loop self-energy Feynman diagrams, which are calculated with differential equations. The results are expressed in terms of harmonic polylogarithms, enabling fast and accurate evaluation. The third-order QCD corrections decrease the LO decay width by 0.667%, and the scale uncertainty is reduced by half compared to the NNLO result. The most precise prediction for the top-quark width is now 1.321 GeV for $m_t=172.69$ GeV. Additionally, we obtain the third-order QCD corrections to the dilepton invariant mass spectrum and decay width in the semileptonic $b\to u$ transition.

   hep-phhep-exPRD(2024)·34 citations
3. 03*

   Quantum transport theory for neutrinos with flavor and particle-antiparticle mixing

   Kimmo Kainulainen🇫🇮 · Harri Parkkinen🇫🇮

   We derive quantum kinetic equations for mixing neutrinos including consistent forward scattering terms and collision integrals for coherent neutrino states. In practice, we reduce the general Kadanoff--Baym equations in a few clearly justified steps to a generalized density matrix equation that describes both the flavour- and particle-antiparticle coherences and is valid for arbitrary neutrino masses and kinematics. We then reduce this equation to a simpler particle-antiparticle diagonal limit and eventually to the ultra-relativistic limit. Our derivation includes simple Feynman rules for computing collision integrals with the coherence information. We also expose a novel spectral shell structure underlying the mixing phenomenon and quantify how the prior information on the system impacts on the QKE's, leading to a direct effect on its evolution. Our results can be used for example to accurately model neutrino distributions in hot and dense environments and to study the production and decay of mixing heavy neutrinos in colliders.

   hep-phastro-ph.HEhep-thJHEP(2024)·11 citations
4. 04*

   Tensor Loop Reduction via the Baikov Representation and an Auxiliary Vector

   Liang Zhang🇨🇳

   In this paper, we introduce a simple and efficient approach for the general reduction of one-loop integrals. Our method employs the introduction of an auxiliary vector and the identification of the tensor structure as an auxiliary propagator. This key insight allows us to express a wide range of one-loop integrals, encompassing both tensor structures and higher poles, in the Baikov representation. By establishing an integral-by-parts (IBP) relation, we derive a recursive formula that systematically solves the one-loop reduction problem, even in the presence of various degenerate cases. Our proposed strategy is characterized by its simplicity and effectiveness, offering a significant advancement in the field of one-loop calculations.

   hep-phhep-thPRD(2024)·3 citations
5. 05*

   Electromagnetic properties of the ${\Sigma }_c(2800{)}^{+}$ and ${\Lambda }_c(2940{)}^{+}$ states via light-cone QCD

   U. Özdem🇹🇷

   The ${\Sigma }_c(2800{)}^{+}$ and ${\Lambda }_c(2940{)}^{+}$ states are among the most interesting and intriguing particles whose internal structures have not yet been elucidated. Inspired by this, the magnetic dipole moments of the ${\Sigma }_c(2800{)}^{+}$ and ${\Lambda }_c(2940{)}^{+}$ states with quantum numbers $J^P={\frac{1}{2}}^{-}$ and $J^P={\frac{3}{2}}^{-}$, respectively, are analyzed in the framework of QCD light-cone sum rules, assuming that they have a molecule composed of a nucleon and a $D^{(\ast )}$ meson. The magnetic dipole moments are obtained as ${\mu }_{{\Sigma }_c^{+}}=0.26\pm 0.05{\mu }_N$ and ${\mu }_{{\Lambda }_c^{+}}=-0.31\pm 0.04{\mu }_N$. The magnetic dipole moment is the leading-order response of a bound system to a weak external magnetic field. It therefore offers an excellent platform to explore the inner organization of hadrons governed by the quark-gluon dynamics of QCD. Comparison of the findings of this analysis with future experimental results on the magnetic dipole moments of the ${\Sigma }_c(2800{)}^{+}$ and ${\Lambda }_c(2940{)}^{+}$ states may shed light on the nature and internal organization of these states. The electric quadrupole and magnetic octupole moments of the ${\Lambda }_c(2940{)}^{+}$ states have also been calculated, and these values are determined to be ${\mathcal{Q}}_{{\Lambda }_c^{+}}=(0.65\pm 0.25)\times 10^{-3}$~fm${}^2$ and ${\mathcal{O}}_{{\Lambda }_c^{+}}=-(0.38\pm 0.10)\times 10^{-3}$~fm${}^3$, respectively. The values of the electric quadrupole and magnetic octupole moments show a non-spherical charge distribution. We hope that our estimates of the electromagnetic properties of the ${\Sigma }_c(2800{)}^{+}$ and ${\Lambda }_c(2940{)}^{+}$ states, together with the results of other theoretical studies of the spectroscopic parameters of these states, will be useful for their search in future experiments and will help us to define the exact internal structures of these states.

   hep-phhep-exhep-latEPJC(2023)·13 citations
6. 06*

   Radiative $B$ to axial-vector meson decays at NLO in Soft-Collinear Effective Theory

   Arslan Sikandar🇵🇰 · M. Jamil Aslam🇵🇰 · Ishtiaq Ahmed🇵🇰 · Saba Shafaq🇵🇰

   The rare decay $B\to A\gamma$, with $A$ representing axial-vector mesons such as $K_1(1270),K_1(1400),b_1(1300),a_1(1260)$, is studied at next-to-leading order (NLO) in soft collinear effective theory (SCET). The large outgoing meson energy encourages the study of the decay with an appropriate factorization scheme that separates the factorizable and non-factorizable parts systematically. We have analyzed the leading-power and $\mathcal{O}({\alpha }_s)$ diagrams that contribute to matching to SCET${}_I$. The new intermediate theory is matched onto SCET${}_{II}$ and the running of SCET${}_I$ operators is performed to sum large perturbative logarithms. The values of soft-overlap function ${\zeta }_{\perp }$ for $K_1(1270,1400),a_1$ and $b_1$ mesons are estimated from the light cone-sum-rules (LCSR), and later using it the corresponding branching fractions for $B\to \left(K_1(1270,1400),a_1,b_1\right)\gamma$ decays are calculated. We find that in case of $B\to K_1(1270,1400)\gamma$ decays the results are in good agreement with their experimental measurements. Also the estimated values of the branching ratios of the $B\to (b_1,a_1)\gamma$ decays are potentially large to be measured at the LHCb and future B-factories.

   hep-phJ.Phys.G(2021)·4 citations
7. 07*

   $W$ and $Z$ Boson Pair Production at Electron-Positron Colliders in Gauge-Higgs Unification

   Naoki Yamatsu🇹🇼 · Shuichiro Funatsu🇯🇵 · Hisaki Hatanaka🇯🇵 · Yutaka Hosotani🇯🇵 · Yuta Orikasa🇨🇿

   We examine $W$ and $Z$ boson pair production processes at electron-positron collider experiments in the $SU(3{)}_C\times SO(5{)}_W\times U(1{)}_X$ gauge-Higgs unification (GHU) model. We find that the deviation of the total cross section for the $e^{-}{e}^{+}\to W^{-}{W}^{+}$ process from the Standard Model (SM) in the GHU model with parameter sets, which are consistent with the current experiments, is about 0.5% to 1.5% and 0.6% to 2.2% for $\sqrt{s}=250$GeV and 500GeV, respectively, depending on the initial electron and positron polarization. We find that for the $e^{-}{e}^{+}\to ZZ$ process the deviation from the SM in the GHU model is at most 1%. We find that unitality bound for the $e^{-}{e}^{+}\to W^{-}{W}^{+}$ process is satisfied in the GHU model as in the SM, as a consequence of the relationship among coupling constants.

   hep-phPRD(2023)·9 citations
8. 08*

   Contribution of Majoron to Hubble tension in gauged U(1)${}_{L_{\mu }-L_{\tau }}$ Model

   Kento Asai🇯🇵 · Tomoya Asano🇯🇵 · Joe Sato🇯🇵 · Masaki J. S. Yang🇯🇵

   In this paper, we analyze parameter regions that can alleviate the Hubble tension in the U(1)${}_{L_{\mu }-L_{\tau }}$ model with the broken lepton number U(1)${}_L$ symmetry. As new particles, this model has a U(1)${}_{L_{\mu }-L_{\tau }}$ gauge boson $Z^{\prime }$ and a Majoron $\varphi$, which can affect the early universe and the effective number of neutrino species $N_{\mathrm{eff}}$. If $Z^{\prime }$ and $\varphi$ simultaneously exist in the early universe, $Z^{\prime }$-$\varphi$ interaction processes such as $Z^{\prime }{\nu }_{\alpha }\leftrightarrow \varphi {\bar{\nu }}_{\beta }$ occur. The comparison of $N_{\mathrm{eff}}$ between the cases with and without the $Z^{\prime }$-$\varphi$ interaction processes shows that these processes make a small contribution of $\mathcal{O}(10^{-4})$ to $N_{\mathrm{eff}}$, and it does not need to be considered for the alleviation of the Hubble tension. Based on these facts, we calculated $N_{\mathrm{eff}}$ for various Majoron parameters without the $Z^{\prime }$-$\varphi$ interaction processes to search parameters that could alleviate the Hubble tension. As a result, we found that the U(1)${}_{L_{\mu }-L_{\tau }}$ gauge boson and Majoron can alleviate the Hubble tension in some parameter regions, and there is a non-trivial synergy contribution between $Z^{\prime }$ and $\varphi$. Moreover, the parameter region with a lighter mass $m_{\varphi }\lesssim 2$ MeV and a larger coupling $\lambda \gtrsim 10^{-8}$ is excluded because it predicts too large $N_{\mathrm{eff}}$, i.e. $N_{\mathrm{eff}}\gtrsim 3.5$. The favored and restricted regions of the Majoron parameters depend on the $Z^{\prime }$ parameters because of the presence of the $Z^{\prime }$ contribution and synergy one.

   hep-phPTEP(2024)·6 citations
9. 09*

   A dispersive estimate of the $a_0(980)$ contribution to hadronic light-by-light scattering in $(g-2{)}_{\mu }$

   Oleksandra Deineka🇩🇪 · Igor Danilkin🇩🇪 · Marc Vanderhaeghen🇩🇪

   A dispersive implementation of the $a_0(980)$ resonance to $(g-2{)}_{\mu }$ requires the knowledge of the double-virtual $S$-wave ${\gamma }^{\ast }{\gamma }^{\ast }\to \pi \eta /K{\bar{K}}_{I=1}$ amplitudes. To obtain these amplitudes we used a modified coupled-channel Muskhelischvili-Omnès formalism, with the input from the left-hand cuts and the hadronic Omnès function. The latter were obtained using a data-driven $N/D$ method in which the fits were performed to the different sets of experimental data on two-photon fusion processes with $\pi \eta$ and $K\bar{K}$ final states. This yields the preliminary dispersive estimate $a_{\mu }^{HLbL}[a_0(980){]}_{resc.}=-0.46(2)\times 10^{-11}$.

   hep-phEPJ Web Conf.(2024)·1 citation
10. 10*

    Probing Inelastic Signatures of Dark Matter Detection via Polarized Nucleus

    Zai Yun🇨🇳 · Junwei Sun🇨🇳 · Bin Zhu🇨🇳 · Xuewen Liu🇨🇳

    We investigate the inelastic signatures of dark matter-nucleus interactions, explicitly focusing on the ramifications of polarization, dark matter splitting, and the Migdal effect. Direct detection experiments, crucial for testing the existence of dark matter, encounter formidable obstacles such as indomitable neutrino backgrounds and the elusive determination of dark matter spin. To overcome these challenges, we explore the potential of polarized-target dark matter scattering, examining the impact of nonvanishing mass splitting and the role of the Migdal effect in detecting light dark matter. Our analysis demonstrates the valuable utility of the polarized triple-differential event rate as an effective tool for studying inelastic dark matter. It enables us to investigate both angular and energy dependencies, providing valuable insights into the scattering process.

    hep-phCPC(2024)·5 citations
11. 11*

    Review of Semileptonic $B$ Anomalies

    Bernat Capdevila🇬🇧 · Andreas Crivellin🇨🇭 · Joaquim Matias🇪🇸

    We review the current status and implications of the anomalies (i.e. deviations from the Standard Model predictions) in semi-leptonic $B$ meson decays, both in the charged and in the neutral current. In $b\to s{\ell }^{+}{\ell }^{-}$ transitions significant tensions between measurements and the Standard Model predictions exist. They are most pronounced in the branching ratios ${\mathcal{B}}_{B\to K{\mu }^{+}{\mu }^{-}}$ and ${\mathcal{B}}_{B_s\to \varphi {\mu }^{+}{\mu }^{-}}$ (albeit quite dependent on the form factors used) as well as in angular observables in $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ (the $P_5^{\prime }$ anomaly). Because the measurements of ${\mathcal{B}}_{B_s\to {\mu }^{+}{\mu }^{-}}$ and of the ratios $R_K$ and $R_{K^{\ast }}$ agree reasonably well with the SM predictions, this points towards (dominantly) lepton flavour universal New Physics coupling vectorially to leptons, i.e. contributions to $C_9^{\mathrm{U}}$. In fact, global fits prefer this scenario over the SM hypothesis by $5.8\sigma$. Concerning $b\to c\tau \nu$ transitions, $R(D)$ and $R(D^{\ast })$ suggest constructive New Physics at the level of $10\%$ (w.r.t. the Standard Model amplitude) with a significance above $3\sigma$. We discuss New Physics explanations of both anomalies separately as well as possible combined explanations. In particular, a left-handed vector current solution to $R(D^{(\ast )})$, either via the $U_1$ leptoquark or the combination of the scalar leptoquarks $S_1$ and $S_3$, leads to an effect in $C_9^{\mathrm{U}}$ via an off-shell penguin with the right sign and magnitude and a combined significance (including a tree-level effect resulting in $C_{9\mu }^{\mathrm{V}}=-C_{10\mu }^{\mathrm{V}}$ and $R(D^{(\ast )})$) of $6.3\sigma$. Such a scenario can be tested with $b\to s{\tau }^{+}{\tau }^{-}$ decays. Finally, we point out an interesting possible correlation of $R(D^{(\ast )})$ with non-leptonic $B$ anomalies.

    hep-phhep-exEur.Phys.J.ST(2023)·106 citations
12. 12*

    Photoproduction of $P$-wave doubly charmed baryon at future $e^{+}{e}^{-}$ collider

    Xi-Jie Zhan🇨🇳 · Xing-Gang Wu🇨🇳 · Xu-Chang Zheng🇨🇳

    The photoproduction of $P$-wave doubly charmed baryon (${\Xi }_{cc}$) is investigated in the context of future high-energy and high-luminosity $e^{+}{e}^{-}$ colliders. The direct photoproduction via the sub-process $\gamma +\gamma \to {\Xi }_{cc}+\bar{c}+\bar{c}$ and the resolved channel $\gamma +g\to {\Xi }_{cc}+\bar{c}+\bar{c}$ are considered. Within the framework of non-relativistic QCD, the calculation encompasses four $P$-wave $(cc)$-diquark configurations: $(cc{)}_{\bar{\text{3}}}[{}^1{P}_1]$, $(cc{)}_{\text{6}}[{}^3{P}_0]$, $(cc{)}_{\text{6}}[{}^3{P}_1]$ and $(cc{)}_{\text{6}}[{}^3{P}_2]$. The two $S$-wave states, $(cc{)}_{\bar{\text{3}}}[{}^3{S}_1]$ and $(cc{)}_{\text{6}}[{}^1{S}_0]$, are also included for comparison. The cross sections, as well as the differential distributions involving transverse momentum, rapidity, and angular variables, have been computed. Numerical results reveal that the resolved photoproduction process plays a significant role and can provide dominant contributions. The photoproduction rate of the $P$-wave ${\Xi }_{cc}$ is approximately one order of magnitude lower than that of the $S$-wave.

    hep-phJHEP(2023)·4 citations
13. 13*

    Three-body strong decays of the $Y(4230)$ via the light-cone QCD sum rules

    Zhi-Gang Wang🇨🇳

    We tentatively assign the $Y(4230)$ as the vector tetraquark state with a relative P-wave between the scalar diquark pair, and explore the three-body strong decays $Y(4230)\to {\bar{D}}^{\ast -}{D}^{\ast 0}{\pi }^{+}$, ${\bar{D}}^{\ast -}{D}^0{\pi }^{+}$, $J/\psi {\pi }^{+}{\pi }^{-}$ and $J/\psi K^{+}{K}^{-}$ with the light-cone QCD sum rules by assuming contact four-meson coupling constants. The resulting partial decay widths are too small to account for the experimental data, and we expect those decays take place through an intermediate meson. We can search for the intermediate states and precisely measure the branching fractions to diagnose the nature of the $Y$ states.

    hep-phInt.J.Mod.Phys.A(2023)·4 citations
14. 14*

    Solving the Naturalness Problem with Feeble Coupled Sectors

    J. Lorenzo Diaz-Cruz🇲🇽

    The discovery of a light Higgs boson means that whatever form new physics takes, it should keep stable the Higgs mass. Besides the well-known solutions to the naturalness problem (Supersymmetry, Conformal symmetry, Compositeness, etc), models that include heavy particles with feeble couplings to the Standard Model (SM) can be considered natural, since the corrections to the Higgs mass remains of the order of the electroweak (EW) scale. This solution can be used for model building too, with realizations that include the see-saw mechanism for neutrino masses and FIMP dark matter models, but it also holds for generic sectors that have Planck-suppressed couplings with the SM. One can also incorporate this solution within the SMEFT framework; the corresponding higher-dimensional operators induce small corrections to both the Higgs mass and its self-coupling, a prediction that can be tested at a future Higgs factory. We present a natural extension of the SMEFT that describes corrections to the SM, while also including a Feeble Coupled Sector aimed to account for the dark cosmos, with predictions for new signals that can be tested too.

    hep-phhep-th0 citations
15. 15*

    Exploring the Mass Radius of ${}^4$He and Implications for Nuclear Structure

    Rong Wang🇨🇳 · Chengdong Han🇨🇳 · Xurong Chen🇨🇳

    In this study, we determine the mass radius of ${}^4$He, a very light nucleus, by examining the near-threshold $\varphi$-meson photoproduction data of the LEPS Collaboration. To assess the gravitational form factor of ${}^4$He, we employ multiple models for the mass distribution, including Yukawa-type, exponential, Gaussian, and uniform functions. The mass radius of ${}^4$He is measured to be $1.70\pm 0.14$ fm, which is approximately equal to the charge radius of ${}^4$He. Surprisingly, in contrast to the findings of the proton, no noticeable discrepancy between the charge radius and the mass radius is noted for the ${}^4$He nucleus. The proton and neutron distributions within ${}^4$He are likely to be identical, confirming its regular tetrahedral structure in a new way. We propose exploring the difference between charge and mass radii as a new approach to examine the nuclear structure.

    hep-phPRC(2024)·20 citations
16. 16*

    Reconstructing parton distribution function based on maximum entropy method

    Sihan Zhang🇨🇳 · Xiaobin Wang🇨🇳 · Tao Lin🇨🇳 · Lei Chang🇨🇳

    A new method based on the maximum entropy principle for reconstructing the parton distribution function (PDF) from moments is proposed. Unlike traditional methods, the new method no longer needs to introduce any artificial assumptions. For the case of moments with errors, we introduce Gaussian functions to soften the constraints of moments. Through a series of tests, the effectiveness and reconstruction efficiency of this new method are evaluated comprehensively. And these tests indicate that this method is reasonable and can achieve high-quality reconstruction with at least the first six moments as input. Finally, we select a set of lattice QCD results regarding moments as input and provide reasonable reconstruction results for the pion.

    hep-phCPC(2024)·8 citations
17. 17*

    Accelerating Markov Chain Monte Carlo sampling with diffusion models

    N. T. Hunt-Smith🇦🇺 · W. Melnitchouk🇺🇸 · F. Ringer🇺🇸 · N. Sato🇺🇸 · A. W Thomas🇦🇺 · M. J. White🇦🇺

    Global fits of physics models require efficient methods for exploring high-dimensional and/or multimodal posterior functions. We introduce a novel method for accelerating Markov Chain Monte Carlo (MCMC) sampling by pairing a Metropolis-Hastings algorithm with a diffusion model that can draw global samples with the aim of approximating the posterior. We briefly review diffusion models in the context of image synthesis before providing a streamlined diffusion model tailored towards low-dimensional data arrays. We then present our adapted Metropolis-Hastings algorithm which combines local proposals with global proposals taken from a diffusion model that is regularly trained on the samples produced during the MCMC run. Our approach leads to a significant reduction in the number of likelihood evaluations required to obtain an accurate representation of the Bayesian posterior across several analytic functions, as well as for a physical example based on a global analysis of parton distribution functions. Our method is extensible to other MCMC techniques, and we briefly compare our method to similar approaches based on normalizing flows. A code implementation can be found at https://github.com/NickHunt-Smith/MCMC-diffusion.

    hep-phstat.MLComput.Phys.Commun.(2024)·13 citations
18. 18*

    The generation of baryon asymmetry and hypermagnetic field by the chiral vortical effect in the presence of sphalerons

    S. Abbaslu🇮🇷 · A. Rezaei🇮🇷 · S. Rostam Zadeh🇮🇷 · S. S. Gousheh🇮🇷

    We show how the temperature-dependent chiral vortical effect can generate hypermagnetic fields and matter-antimatter asymmetries, in the symmetric phase of the early Universe, in the temperature range $100\text{mbox}GeV\le T\le 10\text{mbox}TeV$, even in the presence of the weak sphaleron processes. We take into account all perturbative chirality-flip processes, as well as the nonperturbative Abelian and non-Abelian anomalous effects for all three generations. Using the constraints and conservation laws in the plasma, we reduce the number of required evolution equations. We also simplify the anomalous transport coefficients, accordingly. We consider both monochromatic and continuous spectra for the hypermagnetic and velocity fields to solve the anomalous magnetohydrodynamics equations. We then show that overlapping small transient fluctuations in the temperature of some matter degrees of freedom and vorticity of the plasma can generate a chiral vortical current, resulting in the generation of strong hypermagnetic fields and matter-antimatter asymmetries, all starting from zero initial values. We obtain the baryon asymmetry ${\eta }_B\simeq 5\times 10^{-10}$ and a positive helicity hypermagnetic field with amplitude $B_Y(x)\simeq 10^{19}G$, at the onset of the electroweak phase transition. Although the sphaleron processes tend to washout the generated $(\mathrm{B}+\mathrm{L})$ asymmetry, the anomalous processes prevail and the baryogenesis and leptogenesis occur without $(\mathrm{B}-\mathrm{L})$ violation.

    hep-ph0 citations
19. 19*

    Baryon correlations in Pythia

    Leif Lönnblad🇸🇪 · Harsh Shah🇸🇪

    We present the results from our investigation of angular correlations between baryon pairs in the PYTHIA8 event generator. We show how colour reconnection models and hadronization mechanisms influence such angular correlations and in particular address the effect of gluons on the baryon production mechanism in the Lund string fragmentation model. We conclude by discussing the new theoretical ideas in comparison with the ALICE pp collision results for the baryon angular correlations. We propose a hypothesis for suppressing baryons produced in gluon jets and show how that may influence the angular correlations.

    hep-phEPJC(2023)·8 citations
20. 20*

    ML-Based Top Taggers: Performance, Uncertainty and Impact of Tower & Tracker Data Integration

    Rameswar Sahu🇮🇳 · Kirtiman Ghosh🇮🇳

    Machine learning algorithms have the capacity to discern intricate features directly from raw data. We demonstrated the performance of top taggers built upon three machine learning architectures: a BDT that uses jet-level variables (high-level features, HLF) as input, while a CNN trained on the jet image, and a GNN trained on the particle cloud representation of a jet utilizing the 4-momentum (low-level features, LLF) of the jet constituents as input. We found significant performance enhancement for all three classes of classifiers when trained on combined data from calorimeter towers and tracker detectors. The high resolution of the tracking data not only improved the classifier performance in the high transverse momentum region, but the information about the distribution and composition of charged and neutral constituents of the fat jets and subjets helped identify the quark/gluon origin of sub-jets and hence enhances top tagging efficiency. The LLF-based classifiers, such as CNN and GNN, exhibit significantly better performance when compared to HLF-based classifiers like BDT, especially in the high transverse momentum region. Nevertheless, the LLF-based classifiers trained on constituents' 4-momentum data exhibit substantial dependency on the jet modeling within Monte Carlo generators. The composite classifiers, formed by stacking a BDT on top of a GNN/CNN, not only enhance the performance of LLF-based classifiers but also mitigate the uncertainties stemming from the showering and hadronization model of the event generator. We have conducted a comprehensive study on the influence of the fat jet's reconstruction and labeling procedure on the efficiency of the classifiers. We have shown the variation of the classifier's performance with the transverse momentum of the fat jet.

    hep-phhep-exSciPost Phys.(2024)·10 citations
21. 21*

    Perturbative effective field theory expansions for cosmological phase transitions

    Oliver Gould🇬🇧 · Tuomas V. I. Tenkanen🇸🇪

    Guided by previous non-perturbative lattice simulations of a two-step electroweak phase transition, we reformulate the perturbative analysis of equilibrium thermodynamics for generic cosmological phase transitions in terms of effective field theory (EFT) expansions. Based on thermal scale hierarchies, we argue that the scale of many interesting phase transitions is in-between the soft and ultrasoft energy scales, which have been the focus of studies utilising high-temperature dimensional reduction. The corresponding EFT expansions provide a handle to control the perturbative expansion, and allow us to avoid spurious infrared divergences, imaginary parts, gauge dependence and renormalisation scale dependence that have plagued previous studies. As a direct application, we present a novel approach to two-step electroweak phase transitions, by constructing separate effective descriptions for two consecutive transitions. Our approach provides simple expressions for effective potentials separately in different phases, a numerically inexpensive method to determine thermodynamics, and significantly improves agreement with the non-perturbative lattice simulations.

    hep-phastro-ph.COhep-thJHEP(2024)·61 citations
22. 22*

    Dead cone effect in charm and bottom quark jets

    Stefan Kluth🇩🇪 · Wolfgang Ochs🇩🇪 · Redamy Perez-Ramos🇫🇷

    The evolution of a heavy quark initiated jet is mainly ruled by gluon bremsstrahlung. As a consequence of the dead-cone effect, this radiation is suppressed in the forward direction at angles smaller than that proportional to the heavy quark mass $M_Q$, i.e. ${\Theta }_0=M_Q/E_Q$ at energy $E_Q$ of the primary quark. In this paper, we unveil this effect in charm and bottom quark jets using DELPHI and OPAL data from Z${}^0$ boson decays in $e^{+}{e}^{-}$ annihilation at center of mass energy 91.2 GeV. The analysis of the reconstructed heavy quark fragmentation function in momentum space shows the strong suppression of hadrons at high momenta in such events compared to light quark fragmentation by a factor $\lesssim 1/10$. The amount of this suppression is well reproduced by perturbative QCD (pQCD) within the Modified Leading Logarithmic Aproximation and the compact scheme of Local Parton Hadron Duality (MLLA-LPHD). As a new result, we obtain an almost perfect agreement between the light quark fragmentation functions expected at $W_0\propto M_Q$ from DELPHI and OPAL data with Pythia8 and shed light on the reasons for the existence of the ultra-soft gluon excess at small momentum fraction in comparison with pQCD predictions.

    hep-phhep-exNucl.Part.Phys.Proc.(2024)·3 citations
23. 23*

    Sphaleron damping and effects on vector and axial charge transport in high-temperature QCD plasmas

    Lillian de Bruin🇺🇸 · Sören Schlichting🇩🇪

    We modify the anomalous hydrodynamic equations of motion to account for dissipative effects due to QCD sphaleron transitions. By investigating the linearized hydrodynamic equations, we show that sphaleron transitions lead to nontrivial effects on vector and axial charge transport phenomena in the presence of a magnetic field. Due to the dissipative effects of sphaleron transitions, a wavenumber threshold $k_{\mathrm{CMW}}$ emerges characterizing the onset of chiral magnetic waves. Sphaleron damping also significantly impacts the time evolution of both axial and vector charge perturbations in a QCD plasma in the presence of a magnetic field. Based on our analysis of the linearized hydrodynamic equations, we also investigate the dependence of the vector charge separation on the sphaleron transition rate, which may have implications for the experimental search for the Chiral Magnetic Effect in Heavy Ion Collisions.

    hep-phPRD(2024)·3 citations
24. 24*

    New mechanism for primordial black hole formation from the QCD axion

    Shuailiang Ge🇨🇳 · Jinhui Guo🇨🇳 · Jia Liu🇨🇳

    We present a new mechanism for the primordial black hole (PBH) production within the QCD axion framework. We take the case where the Peccei-Quinn symmetry breaks during inflation, resulting in a $N_{\mathrm{DW}}=1$ string-wall network that re-enters horizon sufficiently late. Therefore, closed axion domain walls naturally arising in the network are sufficiently large to collapse into PBHs. Our numerical simulation shows that $\sim 0.3\%$ of the total wall area is in the form of closed walls. In addition, the relic abundance of dark matter is dominantly accounted for by free axions from the collapse of open walls bounded by strings. In this framework, the abundance of PBH within dark matter is calculated to be $\sim 0.9\%$. This fraction remains unaffected by axion parameters or the re-entering horizon temperature, as it is determined by the fixed proportion of closed walls in the network, governed by the principles of percolation theory. The resultant PBHs uniformly share the same mass, which spans from about $10^{-9}$ to $1$ solar mass, corresponding to the classical QCD axion mass window $10^{-5}-10^{-2}$~eV and the re-entering horizon temperature $300-1$~MeV. Intriguingly, PBHs in this mechanism can naturally account for the ultrashort-timescale gravitational microlensing events observed by the OGLE collaboration.

    hep-phastro-ph.COPRD(2024)·28 citations
25. 25*

    Quasinormal modes of loop quantum black holes near the Planck scale

    Douglas M. Gingrich🇨🇦

    We compare four loop quantum gravity inspired black hole metrics near the Planck scale. Spin 0, 1/2, 1, and 2 field perturbations on these backgrounds are studied. The axial gravitational quasinormal modes are calculated and compared. The time evolution of the ringdown is examined. We also calculate the quasinormal modes in the eikonal limit and compare with the predictions from circular null geodesics.

    ↳ gr-qchep-phhep-thPRD(2024)·15 citations
26. 26*

    Two-Moment Neutrino Flavor Transformation with applications to the Fast Flavor Instability in Neutron Star Mergers

    Evan Grohs🇺🇸 · Sherwood Richers🇺🇸 · Sean M. Couch🇺🇸 · Francois Foucart🇺🇸 · Julien Froustey🇺🇸 · Jim Kneller🇺🇸 · Gail McLaughlin🇺🇸

    Multi-messenger astrophysics has produced a wealth of data with much more to come in the future. This enormous data set will reveal new insights into the physics of core collapse supernovae, neutron star mergers, and many other objects where it is actually possible, if not probable, that new physics is in operation. To tease out different possibilities, we will need to analyze signals from photons, neutrinos, gravitational waves, and chemical elements. This task is made all the more difficult when it is necessary to evolve the neutrino component of the radiation field and associated quantum-mechanical property of flavor in order to model the astrophysical system of interest -- a numerical challenge that has not been addressed to this day. In this work, we take a step in this direction by adopting the technique of angular-integrated moments with a truncated tower of dynamical equations and a closure, convolving the flavor-transformation with spatial transport to evolve the neutrino radiation quantum field. We show that moments capture the dynamical features of fast flavor instabilities in a variety of systems, although our technique is by no means a universal blueprint for solving fast flavor transformation. To evaluate the effectiveness of our moment results, we compare to a more precise particle-in-cell method. Based on our results, we propose areas for improvement and application to complementary techniques in the future.

    ↳ astro-ph.HEhep-phApJ(2024)·43 citations
27. 27*

    Evading no-go for PBH formation and production of SIGWs using Multiple Sharp Transitions in EFT of single field inflation

    Gourab Bhattacharya🇮🇳 · Sayantan Choudhury🇮🇳 · Kritartha Dey🇮🇳 · Saptarshi Ghosh🇮🇳 · Ahaskar Karde🇮🇳 · Navneet Suryaprakash Mishra🇮🇳

    Deploying \textit{multiple sharp transitions} (MSTs) under a unified framework, we investigate the formation of Primordial Black Holes (PBHs) and the production of Scalar Induced Gravitational Waves (SIGWs) by incorporating one-loop corrected renormalized-resummed scalar power spectrum. With effective sound speed parameter, $1\le c_s\le 1.17$, the direct consequence is the generation of PBH masses spanning $M_{\mathrm{PBH}}\sim \mathcal{O}(10^{-31}{M}_{\odot }-10^4{M}_{\odot })$, thus evading well known \textit{No-go theorem} on PBH mass. Our results align coherently with the extensive NANOGrav 15-year data and the sensitivities outlined by other terrestrial and space-based experiments (e.g.: LISA, HLVK, BBO, HLV(O3), etc.).

    ↳ astro-ph.COgr-qchep-phhep-thPhys.Dark Univ.(2024)·59 citations
28. 28*

    Constraining broad photon spectrum injections from exotic and astrophysical sources

    Sandeep Kumar Acharya🇬🇧 · Bryce Cyr🇬🇧 · Jens Chluba🇬🇧

    We study the evolution of photon injections with a power-law type spectrum inserted at various epochs of the universe, and obtain constraints on their parameter space from multiple different cosmological probes. Our work is motivated by the realistic possibility of having extended photon spectra from astrophysical and exotic sources. Going beyond a $\delta$-function like approximation, the physics becomes richer and the constraining power of cosmological probes starts to depend on the photon injection history in a complex way. As a toy model, we first consider a decaying particle scenario, and then generalize to a more model independent power law type injection in redshift. Different combinations of our parameters can be mapped to a wide variety of realistic astrophysical and exotic sources, providing useful benchmarks for study in future work.

    ↳ astro-ph.COastro-ph.HEhep-phMNRAS·4 citations
29. 29*

    Asymptotic analysis of Einstein-Æther theory and its memory effects: the linearized case

    Shaoqi Hou🇨🇳 · Anzhong Wang🇺🇸 · Zong-Hong Zhu🇨🇳

    This work analyzes the asymptotic behaviors of the asymptotically flat solutions of Einstein-æther theory in the linear case. The vacuum solutions for the tensor, vector, and scalar modes are first obtained, written as sums of various multipolar moments. The suitable coordinate transformations are then determined, and the so-called pseudo-Newman-Unti coordinate systems are constructed for all radiative modes. In these coordinates, it is easy to identify the asymptotic symmetries. It turns out that all three kinds of modes possess the familiar Bondi-Metzner-Sachs symmetries or the extensions as in general relativity. Moreover, there also exist the \emph{subleading} asymptotic symmetries parameterized by a time-independent vector field on a unit 2-sphere. The memory effects are also identified. The tensor gravitational wave also excites similar displacement, spin, and center-of-mass memories to those in general relativity. New memory effects due to the vector and scalar modes exist. The subleading asymptotic symmetry is related to the (leading) vector displacement memory effect, which can be viewed as a linear combination of the electric-type and magnetic-type memory effects. However, the scalar memory effect seems to have nothing to do with the asymptotic symmetries at least in the linearized theory.

    ↳ gr-qchep-phhep-thPRD(2024)·14 citations
30. 30*

    Resolving the $R_{\mathrm{pA}}$ and $v_2$ puzzle of $D^0$ mesons in $p-$Pb collisions

    Chao Zhang🇨🇳 · Zi-Wei Lin🇺🇸 · Liang Zheng🇨🇳 · Shusu Shi🇨🇳

    It has been difficult to reconcile the experimental data on the $D^0$ meson nuclear modification factor and elliptic flow in $p-$Pb collisions at LHC energies. Here we study these observables with the string melting version of a multi-phase transport model, which has been improved with the implementation of the Cronin effect (or transverse momentum broadening) and independent fragmentation for charm quarks. Using a strong Cronin effect allows us to provide the first simultaneous description of the $D^0$ meson $R_{\mathrm{pA}}$ and $v_2$ data at $p_{\mathrm{T}}\le$ 8 GeV$/c$. The model also provides a reasonable description of the $D^0$ meson $p_{\mathrm{T}}$ spectra and the low-$p_{\mathrm{T}}$ (below $\sim$ 2 GeV$/c$) charged hadron spectra in $p+p$ and $p-$Pb collisions as well as $R_{\mathrm{pA}}$ and $v_2$ in $p-$Pb collisions. We find that both parton scatterings and the Cronin effect are important for the $D^0$ meson $R_{\mathrm{pA}}$, while parton scatterings are mostly responsible for the $D^0$ meson $v_2$. Our results indicate that it is crucial to include the Cronin effect for the simultaneous description of the $D^0$ meson $R_{\mathrm{pA}}$ and $v_2$. Since the Cronin effect is expected to grow with the system size, this work implies that the Cronin effect could also be important for heavy hadrons in large systems.

    ↳ nucl-thhep-phPoS(2024)·4 citations
31. 31*

    Ab initio calculation of the alpha-particle monopole transition form factor

    Ulf-G. Meißner🇩🇪 · Shihang Shen🇩🇪 · Serdar Elhatisari🇹🇷 · Dean Lee🇺🇸

    We present a parameter-free ab initio calculation of the $\alpha$-particle monopole transition form factor in the framework of nuclear lattice effective field theory. We use a minimal nuclear interaction that was previously used to reproduce the ground state properties of light nuclei, medium-mass nuclei, and neutron matter simultaneously with no more than a few percent error in the energies and charge radii. The results for the monopole transition form factor are in good agreement with recent precision data from Mainz.

    ↳ nucl-thhep-lathep-phnucl-exPRL(2024)·35 citations
32. 32*

    Cosmological complexity of the modified dispersion relation

    Tao Li🇨🇳 · Lei-Hua Liu🇨🇳

    Complexity will be more and more essential in high-energy physics. It is naturally extended into the very early universe. Considering the universe as a quantum chaotic system, the curvature perturbation of the scalar field is identified with the two-mode squeezed state. By solving the Schr$\ddot{o}$dinger equation, one can obtain the numerical solutions of the angle parameter and squeezing parameter. The solution of the squeezing parameter mainly determines the evolution of complexity. Our numeric indicates that the complexity of the modified dispersion relation will have a non-linear pattern after the horizon exits. Meanwhile, its corresponding Lyapunov index is also larger compared with the standard case. During the inflationary period, the complexity will irregularly oscillate and its scrambling time is also shorter compared with the standard case. Since the modified dispersion relation can be dubbed as the consequences of various frameworks of quantum gravity, it could be applicable to these frameworks. Finally, one can expect the framework of quantum gravity will lead to the fruitful evolution of complexity, which guides us in distinguishing various inflationary models.

    ↳ gr-qcastro-ph.COhep-phhep-th+1PLB(2024)·20 citations
33. 33*

    Chiral crossover vs chiral density wave in dense nuclear matter

    Savvas Pitsinigkos🇬🇧 · Andreas Schmitt🇬🇧

    We employ a model based on nucleonic and mesonic degrees of freedom to discuss the competition between isotropic and anisotropic phases in cold and dense matter. Assuming isotropy, the model exhibits a chiral phase transition which is of second order in the chiral limit and becomes a crossover in the case of a realistic pion mass. This observation crucially depends on the presence of the nucleonic vacuum contribution. Allowing for an anisotropic phase in the form of a chiral density wave can disrupt the smooth crossover. We identify the regions in the parameter space of the model where a chiral density wave is energetically preferred. A high-density re-appearance of the chiral density wave with unphysical behavior, as seen in previous studies, is avoided by a suitable renormalization scheme. A nonzero pion mass tends to disfavor the anisotropic phase compared to the chiral limit and we find that, within our model, the chiral density wave is only realized for baryon densities of at least about 6 times nuclear saturation density.

    ↳ nucl-thhep-phPRD(2024)·9 citations
34. 34*

    On the anisotropies of the cosmological gravitational-wave background from pulsar timing array observations

    Ran Ding🇨🇳 · Chi Tian🇨🇳

    Significant evidence for a stochastic gravitational-wave background has recently been reported by several Pulsar Timing Array observations. These studies have shown that, in addition to astrophysical explanations based on supermassive black hole binaries (SMBHBs), cosmological origins are considered equally important sources for these signals. To further explore these cosmological sources, in this study, we discuss the anisotropies in the cosmological gravitational wave background (CGWB) in a model-independent way. Taking the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 15-year dataset as a benchmark, we estimate the angular power spectra of the CGWB and their cross-correlations with cosmic microwave background (CMB) fluctuations and weak gravitational lensing. We find that the NANOGrav 15-year data implies suppressed Sachs-Wolf (SW) effects in the CGBW spectrum, leading to a marginally negative cross-correlation with the CMB at large scales. This procedure is applicable to signals introduced by different early universe processes and is potentially useful for identifying unique features about anisotropies of CGWB from future space-based interferometers and astrometric measurements.

    ↳ astro-ph.COhep-phJCAP(2024)·10 citations
35. 35*

    Binary neutron star mergers in massive scalar-tensor theory: Quasi-equilibrium states and dynamical enhancement of the scalarization

    Hao-Jui Kuan🇩🇪 · Karim Van Aelst🇩🇪 · Alan Tsz-Lok Lam🇩🇪 · Masaru Shibata🇩🇪

    We study quasi-equilibrium sequences of binary neutron stars in the framework of Damour-Esposito-Farese-type scalar-tensor theory of gravity with a massive scalar field, paying particular attention to the case where neutron stars are already spontaneously scalarized at distant orbits, i.e., in the high coupling constant case. Although scalar effects are largely quenched when the separation $a$ is $\gtrsim 3$--$6$ times of the Compton length-scale that is defined by the scalar mass, we show that the interaction between the scalar fields of the two neutron stars generates a scalar cloud surrounding the binary at the price of orbital energy when $a\lesssim 3$--$6$ times of the Compton length-scale. This enables us to constrain the scalar mass $m_{\varphi }$ from gravitational-wave observations of binary neutron star mergers by inspecting the dephasing due to such phenomenon. In particular, the event GW170817 is suggestive of a constraint of $m_{\varphi }\gtrsim 10^{-11}$ eV and the coupling strength should be mild if the neutron stars in this system were spontaneously scalarized.

    ↳ gr-qchep-phPRD(2023)·24 citations
36. 36*

    Evolution of Efimov States

    Sebastian M. Dawid🇺🇸 · Md Habib E Islam🇺🇸 · Raúl A. Briceño🇺🇸 · Andrew W. Jackura🇺🇸

    The Efimov phenomenon manifests itself as an emergent discrete scaling symmetry in the quantum three-body problem. In the unitarity limit, it leads to an infinite tower of three-body bound states with energies forming a geometric sequence. In this work, we study the evolution of these so-called Efimov states using relativistic scattering theory. We identify them as poles of the three-particle $S$ matrix and trace their trajectories in the complex energy plane as they evolve from virtual states through bound states to resonances. We dial the scattering parameters toward the unitarity limit and observe the emergence of the universal scaling of energies and couplings -- a behavior known from the non-relativistic case. Interestingly, we find that Efimov resonances follow unusual, cyclic trajectories accumulating at the three-body threshold and then disappear at some values of the two-body scattering length. We propose a partial resolution to this "missing states" problem.

    ↳ nucl-thhep-lathep-phphysics.atom-phPRA(2024)·29 citations
37. 37*

    Thermodynamics of an updated hadronic resonance list and influence on hadronic transport

    Jordi Salinas San Martín🇺🇸 · Renan Hirayama🇩🇪 · Jan Hammelmann🇩🇪 · Jamie M. Karthein🇺🇸 · Paolo Parotto🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Claudia Ratti🇺🇸 · Hannah Elfner🇩🇪

    Hadron lists based on experimental studies summarized by the Particle Data Group (PDG) are a crucial input for the equation of state and thermal models used in the study of strongly-interacting matter produced in heavy-ion collisions. Modeling of these strongly-interacting systems is carried out via hydrodynamical simulations, which are followed by hadronic transport codes that also require a hadronic list as input. To remain consistent throughout the different stages of modeling of a heavy-ion collision, the same hadron list with its corresponding decays must be used at each step. It has been shown that even the most uncertain states listed in the PDG from 2016 are required to reproduce partial pressures and susceptibilities from Lattice Quantum Chromodynamics with the hadronic list known as the PDG2016+. Here, we update the hadronic list for use in heavy-ion collision modeling by including the latest experimental information for all states listed in the Particle Data Booklet in 2021. We then compare our new list, called PDG2021+, to Lattice Quantum Chromodynamics results and find that it achieves even better agreement with the first principles calculations than the PDG2016+ list. Furthermore, we develop a novel scheme based on intermediate decay channels that allows for only binary decays, such that PDG2021+ will be compatible with the hadronic transport framework SMASH. Finally, we use these results to make comparisons to experimental data and discuss the impact on particle yields and spectra.

    ↳ nucl-thhep-phnucl-ex27 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.