Mon·Feb 25, 2019Monday·February 25, 2019

1. 01*

   Natural quark mixing and inverse seesaw in a left-right model with an axion

   Alex G. Dias🇧🇷 · Julio Leite🇧🇷

   We consider a minimal left-right model with a Peccei-Quinn symmetry, where generalised charge conjugation plays the role of the left-right symmetry. We show how the spontaneous breaking of the Peccei-Quinn symmetry by a scalar singlet can provide us with solutions not only to the strong CP and dark matter problems but can also help to generate naturally suppressed off-diagonal CKM elements and small neutrino masses via the inverse seesaw mechanism. For this, we make use of an economical scalar sector composed of a bi-doublet, two doublets and a singlet only. As a result of the new gauge bosons and neutrinos, the neutrinoless double beta decay, as well as lepton flavour violating processes, receives new contributions which can, in principle, become relevant due to the low-scale nature of the inverse seesaw mechanism. The model can easily accommodate all the current data on fermion masses and mixing even if the left-right scale is only high enough to evade the current experimental constraints.

   hep-phJHEP(2019)·3 citations
2. 02*

   Thick Branes in Extra Dimensions and Suppressed Dark Couplings

   Ricardo G. Landim🇺🇸 · Thomas G. Rizzo🇺🇸

   In this paper we show that the interaction between new light dark matter mediators and the SM particles can be naturally suppressed if one employs a single, flat extra dimension (ED). In this setup, the SM fields are localized in a finite width `fat' brane, similar to models of Universal Extra Dimensions (UED), while DM, in turn, is confined to a thin brane at the opposite end of the ED interval. Including brane localized kinetic terms on the fat brane for the mediator fields, the resulting coupling between the SM and these light mediators can be several orders of magnitude smaller than the corresponding ones between the mediators and DM which we assume to be a typical gauge coupling. We investigate the implications of this scenario for both vector (i.e., dark photon, DP) and scalar mediator fields in the 5-D bulk. In this setup kinetic mixing, which is usually employed to suppress light mediator couplings, is not required. Here we assume that the SM particles couple to the DP via their $B-L$ charges while the DP couples to the DM via a dark charge. Both the vector DP couplings and the corresponding Higgs portal couplings with the SM are shown to be natural small in magnitude with a size dependent on ratio of the 5-D compactification radius, $R^{-1}\sim 0.1-1$ GeV, and the SM brane thickness, $L^{-1}\sim 2-10$ TeV, a range chosen to avoid LHC and other experimental constraints. In this framework one can obtain the observed value of the DM relic abundance for a wide range of parameter choices, while the constrains due to direct DM detection and the invisible width of the Higgs do not impose significant challenges to the model. Finally, this mechanism can lead to distinct signatures in both present and upcoming experiments as it combines some common features of UED and DP models in a single ED setup.

   hep-phastro-ph.COhep-thJHEP(2019)·12 citations
3. 03*

   Flow and vorticity with varying chemical potential in relativistic heavy ion collisions

   Abhisek Saha🇮🇳 · Soma Sanyal🇮🇳

   We study the vorticity patterns in relativistic heavy ion collisions with respect to the collision energy. The collision energy is related to the chemical potential used in the thermal - statistical models that assume approximate chemical equilibrium after the relativistic collision. We use the multiphase transport model (AMPT) to study the vorticity in the initial parton phase as well as the final hadronic phase of the relativistic heavy ion collision. We find that as the chemical potential increases,the vortices are larger in size. Using different definitions of vorticity, we find that vorticity plays a greater role at lower collision energies than at higher collision energies. We also look at other effects of the flow patterns related to the bulk viscosity and the shear viscosity at different collision energies. We find that the shear viscosity obtained is almost a constant with a small decrease at higher collision energies. We also look at the elliptic flow as it is related to viscous effects in the final stages after the collision. Our results indicate that viscosity plays a greater role at higher chemical potential and lower collision energies.

   hep-phnucl-thIJMPE(2020)·7 citations
4. 04*

   Associated production of ${\chi }_c$ pairs with a gluon in the collinear-factorization approach

   Izabela Babiarz🇵🇱 · Wolfgang Schäfer🇵🇱 · Antoni Szczurek🇵🇱

   We calculate cross section for production of ${\chi }_c$ pairs in proton-proton collisions. The cross section for the $gg\to {\chi }_{c{J}_1}{\chi }_{c{J}_2}$ is considerably smaller (especially for ${\chi }_{c1}{\chi }_{c1}$ final state) than that obtained recently in the $k_T$-factorization approach. We calculate therefore next-to-leading order contributions with ${\chi }_c$ pair and one extra associated (mini-)jet. We find these contributions to be much larger than those for the $2\to 2$ contribution. Especially the emission of a leading gluon (carrying a large momentum fraction of one of the incoming gluons) are important. These emissions in the $k_T$-factorization approach are absorbed into the initial state unintegrated gluon distributions. A smaller contribution to the cross section comes from the production of central gluons emitted with rapidities between the ${\chi }_c$-mesons. They do lead, however, to an enhancement of the ${\chi }_c$-pair production at large rapidity distance between the mesons. Our present study explains the size of the cross section for the ${\chi }_c$ pair production obtained previously in the $k_T$-factorization approach. Several differential distributions are presented.

   hep-phPRD(2019)·4 citations
5. 05*

   HEJ 2: High Energy Resummation for Hadron Colliders

   Jeppe R. Andersen🇬🇧 · Tuomas Hapola🇬🇧 · Marian Heil🇬🇧 · Andreas Maier🇩🇪 · Jennifer Smillie🇬🇧

   We present HEJ 2, a new implementation of the High Energy Jets formalism for high-energy resummation in hadron-collider processes as a flexible Monte Carlo event generator. In combination with a conventional fixed-order event generator, HEJ 2 can be used to obtain greatly improved predictions for a number of phenomenologically important processes by adding all-order logarithmic corrections in $\hat{s}/p_{\perp }^2$. A prime example for such a process is the gluon-fusion production of a Higgs boson in association with widely separated jets, which constitutes the dominant background to Higgs boson production in weak-boson fusion.

   hep-phComput.Phys.Commun.(2019)·16 citations
6. 06*

   Transversity distributions from difference asymmetries in semi-inclusive DIS

   V. Barone🇮🇹 · F. Bradamante🇮🇹 · A. Bressan🇮🇹 · A. Kerbizi🇮🇹 · A. Martin🇮🇹 · A. Moretti🇮🇹 · J. Matousek🇮🇹 · G. Sbrizzai🇮🇹

   In recent years information on the transversity distribution $h_1$ has been obtained combining the Collins asymmetry results from semi-inclusive deep inelastic scattering (SIDIS) data on transversely polarized nucleon targets with the information on the fragmentation function of a transversely polarized quark from the asymmetries measured in $e^{+}{e}^{-}$ annihilation into hadrons. An alternative method was proposed long time ago, which does not require the $e^{+}{e}^{-}$ data, but allows one to get ratios of the $u$ and $d$ quark transversity distributions from the SIDIS data alone. The method utilizes the ratio of the difference of the Collins asymmetries of positively and negatively charged hadrons produced on transversely polarized proton and deuteron targets. We have applied this method to the COMPASS proton and deuteron data, and extracted the ratio $h_1^d/h_1^u$. The results are compared to those obtained in a previous point--by--point extraction based both on SIDIS and $e^{+}{e}^{-}$ data.

   hep-phPRD(2019)·11 citations
7. 07*

   Extraction of unpolarized quark transverse momentum dependent parton distributions from Drell-Yan/Z-boson production

   Valerio Bertone🇮🇹 · Ignazio Scimemi🇪🇸 · Alexey Vladimirov🇩🇪

   We present the extraction of unpolarized quark transverse momentum dependent parton distribution functions (TMDPDFs) and the non-perturbative part of TMD evolution kernel from the global analysis of Drell-Yan and $Z$-boson production data. The analysis is performed at the next-to-next-to-leading order (NNLO) in perturbative QCD, using the $\zeta$-prescription. The estimation of the error-propagation from the experimental uncertainties to non-perturbative function is made by the replica method. The importance of the inclusion of the precise LHC data and its influence on the determination of non-perturbative functions is discussed.

   hep-phJHEP(2019)·153 citations
8. 08*

   Compact Star of Holographic Nuclear Matter and GW170817

   Kilar Zhang🇹🇼 · Takayuki Hirayama🇯🇵 · Ling-Wei Luo🇹🇼 · Feng-Li Lin🇹🇼

   We use a holographic model of quantum chromodynamics to extract the equation of state (EoS) for the cold nuclear matter of moderate baryon density. This model is based on the Sakai-Sugimoto model in the deconfined Witten's geometry with the additional point-like D4-brane instanton configuration as the holographic baryons. Our EoS takes the following doubly-polytropic form: $ϵ=2.629{\mathcal{A}}^{-0.192}{p}^{1.192}+0.131{\mathcal{A}}^{0.544}{p}^{0.456}$ with $\mathcal{A}$ a tunable parameter of order $10^{-1}$, where $ϵ$ and $p$ are the energy density and pressure, respectively. The sound speed satisfies the causality constraint and breaks the sound barrier. We solve the Tolman-Oppenheimer-Volkoff equations for the compact stars and obtain the reasonable compactness for the proper choices of $\mathcal{A}$. Based on these configurations we further calculate the tidal deformability of the single and binary stars. We find our results agree with the inferred values of LIGO/Virgo data analysis for GW170817.

   hep-phastro-ph.HEgr-qchep-thPLB(2020)·21 citations
9. 09*

   Anomaly-free Model Building with Algebraic Geometry

   Johan Rathsman🇸🇪 · Felix Tellander🇸🇪

   We present a method to find anomaly-free gauged Froggatt-Nielsen type models using results from algebraic geometry. These methods should be of general interest for model building beyond the Standard Model (SM) when rational charges are required. We consider models with a gauged $U(1)$ flavor symmetry with one flavon and two Higgs doublets and three right-handed SM singlets to provide three model examples based on different physical assumptions. The models we study are: anomaly-free with no SM neutral heavy chiral fermions, anomaly-free with SM neutral heavy chiral fermions, and supersymmetric with SM neutral heavy chiral fermions where the anomalies cancel via the Green-Schwarz mechanism. With these different models we show how algebraic methods may be used in model building; both to reduce the charge constraints by calculation of Gröbner bases, and to find rational solutions to cubic equations using Mordell-Weil generators. Using these tools we find three phenomenologically viable models explaining the observed flavor structure.

   hep-phPRD(2019)·24 citations
10. 10*

    A non-universal $U(1{)}_X$ gauge extension to the MSSM

    J.S. Alvarado🇨🇴 · Carlos E. Diaz🇨🇴 · R. Martinez🇨🇴

    We propose a supersymmetric extension of the anomaly-free and three families nonuniversal $U(1)$ model, with the inclusion of four Higgs doublets and four Higgs singlets. The quark sector is extended by adding three exotic quark singlets, while the lepton sector includes two exotic charged lepton singlets, three right-handed neutrinos and three sterile Majorana neutrinos to obtain the fermionic mass spectrum. By implementing an additional ${\mathbb{Z}}_2$ symmetry, the Yukawa coupling terms are suited in such a way that the fermion mass hierarchy is obtained without fine-tuning. The effective mass matrix for SM neutrinos is fitted to current neutrino oscillation data to check the consistency of the model with experimental evidence, obtaining that the normal-ordering scheme is preferred over the inverse ones. The electron and up, down and strange quarks are massless at tree level, but they get masses through radiative correction at one loop level coming from the sleptons and Higgsinos contributions. We show that the model predicts a like-Higgs SM mass at electroweak scale by using the VEV according to the symmetry breaking and fermion masses.

    hep-phPRD(2019)·6 citations
11. 11*

    ParticleNet: Jet Tagging via Particle Clouds

    Huilin Qu🇺🇸 · Loukas Gouskos🇨🇭

    How to represent a jet is at the core of machine learning on jet physics. Inspired by the notion of point clouds, we propose a new approach that considers a jet as an unordered set of its constituent particles, effectively a "particle cloud". Such a particle cloud representation of jets is efficient in incorporating raw information of jets and also explicitly respects the permutation symmetry. Based on the particle cloud representation, we propose ParticleNet, a customized neural network architecture using Dynamic Graph Convolutional Neural Network for jet tagging problems. The ParticleNet architecture achieves state-of-the-art performance on two representative jet tagging benchmarks and is improved significantly over existing methods.

    hep-phcs.CVhep-exPRD(2020)·735 citations
12. 12*

    $Z^{\prime }$s in neutrino scattering at DUNE

    Peter Ballett🇬🇧 · Matheus Hostert🇬🇧 · Silvia Pascoli🇬🇧 · Yuber F. Perez-Gonzalez🇺🇸 · Zahra Tabrizi🇧🇷 · Renata Zukanovich Funchal🇧🇷

    Novel leptophilic neutral currents can be tested at upcoming neutrino oscillation experiments using two complementary processes, neutrino trident production and neutrino-electron ($\nu -e$) elastic scattering. Considering generic anomaly-free $U(1)$ extensions of the Standard Model, we discuss the characteristics of $\nu -e$ scattering as well as $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ trident production at the DUNE near detector in the presence of such BSM scenarios. We then determine the sensitivity of DUNE in constraining the well-known $L_e-L_{\mu }$ and $L_{\mu }-L_{\tau }$ models. We conclude that DUNE will be able to probe these leptophilic models with unprecedented sensitivity, covering unproved explanations of the $(g-2{)}_{\mu }$ discrepancy.

    hep-phPRD(2019)·89 citations
13. 13*

    Current and future perspectives of positronium and muonium spectroscopy as dark sectors probe

    Claudia Frugiuele🇮🇱 · Jesús Pérez-Ríos🇩🇪 · Clara Peset🇩🇪

    Positronium and Muonium are purely leptonic atoms and hence free of an internal sub-structure. This qualifies them as potentially well suited systems to probe the existence of physics beyond the Standard Model. We hence carry out a comprehensive study of the sensitivity of current Positronium and Muonium precision spectroscopy to several new physics scenarios. By taking properly into account existing experimental and astrophysical probes, we define clear experimental targets to probe new physics via precise spectroscopy. For Positronium we find that, in order for the spectroscopy bounds to reach a sensitivity comparable to the electron gyromagnetic factor, an improvement of roughly five orders of magnitude from state-of-the-art precision is required, which would be a challenge based on current technology. More promising is instead the potential reach of Muonium spectroscopy: in the next few years experiments like Mu-MASS at PSI will probe new regions of the parameter space testing the existence of medium/short range (MeV and above) spin-dependent and spin-independent dark forces between electrons and muons.

    hep-phhep-exphysics.atom-phPRD(2019)·49 citations
14. 14*

    Ameliorating Higgs Induced Flavor Constraints on TeV Scale $W_R$

    Rabindra N. Mohapatra🇺🇸 · Guanwen Yan🇺🇸 · Yongchao Zhang🇺🇸

    In the TeV scale minimal left-right symmetric model (LRSM) for neutrino masses, there is a tension between the flavor changing Higgs effects which prefer an $SU(2{)}_R$ breaking scale $v_R\gtrsim (15-25)$ TeV depending on whether the theory is kept invariant under charge conjugation ($Q_L\to (Q_R{)}^c$) or under parity ($Q_L\to Q_R$) respectively and an LHC accessible few-TeV range mass of $W_R$ boson which would require $v_R\lesssim 10(15)$ TeV if $g_R/g_L=1(0.65)$. This requires one quartic coupling in the scalar potential to go non-perturbative, posing a theoretical problem if the $W_R$ is discovered at LHC. We propose a simple extension of the minimal LRSM that adds a $B-L=0$ scalar triplet and study how this can ameliorate this tension. We find that such a model is also constrained from various considerations and implies a lower bound on the $W_R$ mass of 8.1 (5.26) TeV for the parity case with $g_R/g_L=1(0.65)$ and 4.85 (3.16) TeV for the case of charge conjugation, if the flavor constraints have to be avoided while keeping all couplings perturbative. These mass ranges are accessible at the high-luminosity LHC. The model also implies new decay mode of $W_R$ to two scalars which is absent in the minimal LRSM. Finally we comment on the impact of such a scalar multiplet for a class of dark matter extension of LRSM discussed in the literature recently.

    hep-phhep-exNPB(2019)·8 citations
15. 15*

    Making dark matter out of light: freeze-in from plasma effects

    Cora Dvorkin🇺🇸 · Tongyan Lin🇺🇸 · Katelin Schutz🇺🇸

    Dark matter (DM) could couple to particles in the Standard Model (SM) through a light vector mediator. In the limit of small coupling, this portal could be responsible for producing the observed DM abundance through a mechanism known as freeze-in. Furthermore, the requisite DM-SM couplings provide a concrete benchmark for direct and indirect searches for DM. In this paper, we present updated calculations of the relic abundance for DM produced by freeze-in through a light vector mediator. We identify an additional production channel: the decay of photons that acquire an in-medium plasma mass. These plasmon decays are a dominant channel for DM production for sub-MeV DM masses, and including this channel leads to a significant reduction in the predicted signal strength for DM searches. Accounting for production from both plasmon decays and annihilations of SM fermions, the DM acquires a highly non-thermal phase space distribution which impacts the cosmology at later times; these cosmological effects will be explored in a companion paper.

    hep-phastro-ph.COPRD(2019)·197 citations
16. 16*

    All-in-one Relaxion, a unified solution to five BSM puzzles

    R.S. Gupta🇬🇧 · J.Y. Reiness🇬🇧 · M. Spannowsky🇬🇧

    We present a unified relaxion solution to the five major outstanding issues in particle physics: the hierarchy problem, dark matter, matter-antimatter asymmetry, neutrino masses and the strong CP problem. The only additional field content in our construction with respect to standard relaxion models is an up-type vector-like fermion pair and three right-handed neutrinos charged under the relaxion shift symmetry. The observed dark matter abundance is generated automatically by oscillations of the relaxion field that begin once it is misaligned from its original stopping point after reheating. The matter-antimatter asymmetry arises from spontaneous baryogenesis induced by the CPT violation due to the rolling of the relaxion after reheating. The CPT violation is communicated to the baryons and leptons via an operator, ${\partial }_{\mu }\varphi J^{\mu }$, where $J^{\mu }$ consists of right-handed neutrino currents arising naturally from a simple neutrino mass model. Finally, the strong CP problem is solved via the Nelson-Barr mechanism, i.e. by imposing CP as a symmetry of the Lagrangian that is broken only spontaneously by the relaxion. The CP breaking is such that although an $\mathcal{O}(1)$ strong CKM phase is generated, the induced strong CP phase is much smaller, i.e., within experimental bounds.

    hep-phPRD(2019)·25 citations
17. 17*

    Fluctuations and correlations in thermal QCD

    E. Megias🇪🇸 · E. Ruiz Arriola🇪🇸 · L.L. Salcedo🇪🇸

    We study the equation of state, fluctuations and static correlators of electric charge, baryon number and strangeness, by considering a realization of the Hadron Resonance Gas model in the light flavor sector of QCD. We emphasize the importance of these observables to study, within this approach, the possible existence of exotic and missing states in the hadron spectrum. Some preliminary results for the baryon spectrum have been obtained within a relativistic quark-diquark model, leading to an overall good agreement with the spectrum obtained with other quark models. Finally, it is conjectured, within the Hadron Resonance Gas approach, the existence of a singularity in the correlators at zero temperature, which turns out to be analogous to the divergence of the partition function at the Hagedorn temperature.

    hep-phhep-latnucl-thNucl.Part.Phys.Proc.(2018)·1 citation
18. 18*

    Soft Gluon Resummation in $t$-channel single top quark production at the LHC

    Qing-Hong Cao🇨🇳 · Peng Sun🇨🇳 · Bin Yan🇺🇸 · C.-P. Yuan🇺🇸 · Feng Yuan🇺🇸

    We present a detailed phenomenological study of the multiple soft gluon radiation for the $t$-channel single top and anti-top quark production at the Large Hadron Collider (LHC). By applying the transverse momentum dependent factorization formalism, large logarithms introduced by small total transverse momentum $q_{\perp }$ of the single-top (anti-top) plus one-jet final state system are resummed to all orders in the expansion of the strong interaction coupling at the accuracy of Next-to-Leading Logarithm. We discuss various kinematical distributions which are sensitive to this effect and find that soft gluon radiation become more important when the final state jet is required to be in the forward region. We show that the main difference from PYTHIA prediction lies on the inclusion of the exact color coherence effect between the initial and final states in our resummation calculation. We further propose to apply the experimental observable ${\varphi }^{\ast }$ to test the effect of multiple gluon radiation in the single-top and anti-top events. The bottom quark mass effect and jet rapidity distribution are also discussed.

    hep-phhep-ex12 citations
19. 19*

    Gravitational waves from compact dark matter objects in the solar system

    C. J. Horowitz🇺🇸 · M. A. Papa🇺🇸 · S. Reddy🇺🇸

    Dark matter could be composed of compact dark objects (CDOs). A close binary of CDOs orbiting in the interior of solar system bodies can be a loud source of gravitational waves (GWs) for the LIGO and VIRGO detectors. We perform the first search ever for this type of signal and rule out close binaries, with separations of order 300 m, orbiting near the center of the Sun with GW frequencies (twice the orbital frequency) between 50 and 550 Hz and CDO masses above $\approx 10^{-9}{M}_{\odot }$. This mass limit is eight orders of magnitude lower than the mass probed in a LIGO search at extra galactic distances.

    ↳ gr-qcastro-ph.HEastro-ph.IMhep-phPLB(2020)·27 citations
20. 20*

    Constraints on Superconducting Cosmic Strings from the Global $21$-cm Signal before Reionization

    Robert Brandenberger🇨🇦 · Bryce Cyr🇨🇦 · Rui Shi🇨🇳

    Electromagnetic radiation from the cusp region of superconducting cosmic strings leads to a radio excess in the photon spectrum in the early universe and can produce a deep absorption feature in the global 21cm signal before the epoch of reionization. We study the constraints on the parameter space of superconducting strings which can be derived by demanding that the absorption feature is not larger in amplitude than what has recently been reported by the EDGES collaboration.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2019)·50 citations
21. 21*

    On Non-Perturbative Unitarity in Gravitational Scattering

    Ivo Sachs🇩🇪 · Tung Tran🇩🇪

    We argue that the tree-level graviton-scalar scattering in the Regge limit is unitarized by non-perturbative effects within General Relativity. At Planckian energy the back reaction of the incoming graviton on the background geometry produces a non-perturbative plane wave which, in turn, softens the UV-behavior. Our amplitude then interpolates between the perturbative graviton-scalar scattering at low energy and scattering on a classical plane wave in the Regge limit.

    ↳ hep-thgr-qchep-phEPJC(2019)·5 citations
22. 22*

    The three-loop Adler $D$-function for $\mathcal{N}=1$ SQCD regularized by dimensional reduction

    S.S.Aleshin🇷🇺 · A.L.Kataev🇷🇺 · K.V.Stepanyantz🇷🇺

    The three-loop Adler $D$-function for $\mathcal{N}=1$ SQCD in the $\overline{\text{mbox}DR}$ scheme is calculated starting from the three-loop result recently obtained with the higher covariant derivative regularization. For this purpose, for the theory regularized by higher derivatives we find a subtraction scheme in which the Green functions coincide with the ones obtained with the dimensional reduction and the modified minimal subtraction prescription for the renormalization of the SQCD coupling constant and of the matter superfields. Also we calculate the $D$-function in the $\overline{\text{mbox}DR}$ scheme for all renormalization constants (including the one for the electromagnetic coupling constant which appears due to the SQCD corrections). It is shown that the results do not satisfy the NSVZ-like equation relating the $D$-function to the anomalous dimension of the matter superfields. However, the NSVZ-like scheme can be constructed with the help of a properly tuned finite renormalization. It is also demonstrated that the three-loop $D$-function defined in terms of the bare couplings with the dimensional reduction does not satisfy the NSVZ-like equation for an arbitrary renormalization prescription. We also investigate a possibility to present the results in the form of the $\beta$-expansion and the scheme dependence of this expansion.

    ↳ hep-thhep-phJHEP(2019)·17 citations
23. 23*

    Observing Eccentricity Oscillations of Binary Black Holes in LISA

    Lisa Randall🇺🇸 · Zhong-Zhi Xianyu🇺🇸

    The tidal force from a third body near a binary system could introduce long-term oscillations in the binary's eccentricity, known as Kozai-Lidov oscillations. We show that the Kozai-Lidov oscillations of stellar-mass black hole binaries have the potential to be observed by LISA. Detections of such binaries will give insights into binary formation channels and also provide an important benchmark of observing Kozai-Lidov oscillations directly.

    ↳ astro-ph.HEgr-qchep-ph58 citations
24. 24*

    The flavor composition of astrophysical neutrinos after 8 years of IceCube: an indication of neutron decay scenario?

    Andrea Palladino🇩🇪

    In this work we present an updated study of the flavor composition suggested by astrophysical neutrinos observed by IceCube. The main novelties compared to previous studies are the following: 1) we use the most recent measurements, namely 8 years of throughgoing muons and 7.5 years of High Energy Starting Events (HESE); 2) we consider a broken power law spectrum, in order to be consistent with the observations between 30 TeV and few PeV; 3) we use the throughgoing muon flux to predict the number of astrophysical HESE tracks. We show that accounting for the three previous elements, the result favors surprisingly the hypothesis of neutrinos produced by neutron decay, disfavoring the standard picture of neutrinos from pion decay at 2.0$\sigma$ and the damped muons regime at $2.6\sigma$, once the atmospheric background is considered. Although the conventional scenario is not yet completely ruled out in the statistically and alternative interpretations are also plausible, such as an energy spectrum characterized by a non trivial shape, this intriguing result may suggest new directions for both theoretical interpretation and experimental search strategies.

    ↳ astro-ph.HEhep-phEPJC(2019)·31 citations
25. 25*

    Some new hints on cosmic-ray propagation from AMS-02 nuclei spectra

    Jia-Shu Niu🇨🇳 · Hui-Fang Xue🇨🇳

    In this work, we considered 2 schemes (a high-rigidity break in primary source injections and a high-rigidity break in diffusion coefficient) to reproduce the newly released AMS-02 nuclei spectra (He, C, N, O, Li, Be, and B) when the rigidity larger than 50 GV. The fitting results show that current data set favors a high-rigidity break at $\sim 325\mathrm{GV}$ in diffusion coefficient rather than a break at $\sim 365\mathrm{GV}$ in primary source injections. Meanwhile, the fitted values of the factors to rescale the cosmic-ray (CR) flux of secondary species/components after propagation show us that the secondary flux are underestimated in current propagation model. It implies that we might locate in a slow diffusion zone, in which the CRs propagate with a small value of diffusion coefficient compared with the averaged value in the galaxy. Another hint from the fitting results show that extra secondary CR nuclei injection may be needed in current data set. All these new hints should be paid more attention in future research.

    ↳ astro-ph.HEhep-phJCAP(2020)·6 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.