Wed·Feb 28, 2018Wednesday·February 28, 2018

1. 01*

   The impact of domain walls on the chiral magnetic effect in hot QCD matter

   Kirill Tuchin🇺🇸

   The Chiral Magnetic Effect (CME) -- the separation of positive and negative electric charges along the direction of the external magnetic field in quark-gluon plasma and other topologically non-trivial media -- is a consequence of the coupling of electrodynamics to the topological gluon field fluctuations that form metastable $CP$-odd domains. In phenomenological models it is usually assumed that the domains are uniform and the influence of the domain walls on the electric current flow is not essential. This paper challenges the latter assumption. A simple model consisting of a uniform spherical domain in a uniform time-dependent magnetic field is introduced and analytically solved. It is shown that (i) no electric current flows into or out of the domain, (ii) the charge separation current, viz. the total electric current flowing inside the domain in the external field direction, is a dissipative Ohm current, (iii) the CME effect can be produced either by the anomalous current or by the boundary conditions on the domain wall and (iv) the charge separation current oscillates in plasma long after the external field decays. These properties are qualitatively different from the CME in an infinite medium.

   hep-phnucl-thPRC(2018)·8 citations
2. 02*

   Hadronic Superpartners from Superconformal and Supersymmetric Algebra

   Marina Nielsen🇧🇷 · Stanley J. Brodsky🇺🇸

   Through the embedding of superconformal quantum mechanics into AdS space, it is possible to construct an effective supersymmetric QCD light-front Hamiltonian for hadrons, which includes a spin-spin interaction between the hadronic constituents. A specific breaking of conformal symmetry determines a unique effective quark-confining potential for light hadrons, as well as remarkable connections between the meson, baryon, and tetraquark spectra. The pion is massless in the chiral limit and has no supersymmetric partner. The excitation spectra of relativistic light-quark meson, baryon and tetraquark bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. Although conformal symmetry is strongly broken by the heavy quark mass, the basic underlying supersymmetric mechanism, which transforms mesons to baryons (and baryons to tetraquarks) into each other, still holds and gives remarkable connections across the entire spectrum of light, heavy-light and double-heavy hadrons. Here we show that all the observed hadrons can be related through this effective supersymmetric QCD, and that it can be used to identify the structure of the new charmonium states.

   hep-phPRD(2018)·62 citations
3. 03*

   Perturbative QCD Analysis of Exclusive Processes $e^{+}{e}^{-}\to VP$ and $e^{+}{e}^{-}\to TP$

   Cai-Dian Lü🇨🇳 · Wei Wang🇨🇳 · Ye Xing🇨🇳 · Qi-An Zhang🇨🇳

   We study the $e^{+}{e}^{-}\to VP$ and $e^{+}{e}^{-}\to TP$ processes in the perturbative QCD approach based on $k_T$ factorization, where the $P,V$ and $T$ denotes a light pseudo-scalar, vector and tensor meson, respectively. We point out in the case of $e^{+}{e}^{-}\to TP$ transition due to charge conjugation invariance, only three channels are allowed: $e^{+}{e}^{-}\to a_2^{\pm }{\pi }^{\mp }$, $e^{+}{e}^{-}\to K_2^{\ast \pm }{K}^{\mp }$ and the V-spin suppressed $e^{+}{e}^{-}\to K_2^{\ast 0}{\bar{K}}^0+{\overline{K}}_2^{\ast 0}{K}^0$. Cross sections of $e^{+}{e}^{-}\to VP$ and $e^{+}{e}^{-}\to TP$ at $\sqrt{s}=3.67$ GeV and $\sqrt{s}=10.58$ GeV are calculated and the invariant mass dependence is found to favor the $1/s^4$ power law. Most of our theoretical results are consistent with the available experimental data and other predictions can be tested at the ongoing BESIII and forthcoming Belle-II experiments.

   hep-phhep-exPRD(2018)·10 citations
4. 04*

   Universal Freezeout Condition for Charged Hadrons in a Hybrid Approach

   O. S. K. Chaturvedi🇮🇳 · P. K. Srivastava🇮🇳 · Arpit Singh🇮🇳 · B. K. Singh🇮🇳

   Hadronic freezeout during the evolution of the medium created in heavy-ion collisions is an important phenomena. It is quite useful to find a universal freezeout condition for each and every nuclear collisions. In this article, we have constructed a hybrid model to calculate the ratio of transverse energy to total mean multiplicity $E_T/N_{ch}$, since this ratio can possibly act as a freezeout condition in heavy-ion collision experiments. Present hybrid model blends two approaches : Tsallis statistics and wounded quark approach. Recently, Tsallis statistics has been reliably used to obtain the transverse momentum distribution of charged hadrons produced in relativistic ion collisions. On the other side it has been shown that the pseudorapidity distribution of charged hadrons can be calculated satisfactorily using the wounded quark model (WQM). We have used this hybrid model to calculate the transverse energy density distributions, $d{E}_T/d\eta$ at midrapidity using charged particle pseudorapidity distributions, $d{N}_{ch}/d\eta$ and mean transverse momentum $⟨p_T⟩$ in various type of nuclear collisions. We found that present hybrid model satisfactorily explains the experimental data whether other models fail to reproduce the data at central and at peripheral collisions simultaneously. Finally, ratio of transverse energy to total mean multiplicity, $E_T/N_{ch}$ has been computed within hybrid model and compared with the available experimental data at RHIC and LHC energies. We observed no explicit dependence of $E_T/N_{ch}$ on energy as well as centrality and thus it can definitely act as a freezeout criteria.

   hep-phEPJA(2018)·3 citations
5. 05*

   Electromagnetic transition form factors of baryons in a relativistic Faddeev approach

   Reinhard Alkofer🇦🇹 · Christian S. Fischer🇩🇪 · Helios Sanchis-Alepuz🇦🇹

   The covariant Faddeev approach which describes baryons as relativistic three-quark bound states and is based on the Dyson-Schwinger and Bethe-Salpeter equations of QCD is briefly reviewed. All elements, including especially the baryons' three-body-wave-functions, the quark propagators and the dressed quark-photon vertex, are calculated from a well-established approximation for the quark-gluon interaction. Selected previous results of this approach for the spectrum and elastic electromagnetic form factors of ground-state baryons and resonances are reported. The main focus of this talk is a presentation and discussion of results from a recent investigation of the electromagnetic transition form factors between ground-state octet and decuplet baryons as well as the octet-only ${\Sigma }^0$ to $\Lambda$ transition.

   hep-phEPJ Web Conf.(2018)·3 citations
6. 06*

   Stability of neutrino parameters and self-complementarity relation with varying SUSY breaking scale

   Konsam Sashikanta Singh🇮🇳 · Subhankar Roy🇮🇳 · Ngangkham Nimai Singh🇮🇳

   The scale at which supersymmetry (SUSY) breaks ($m_s$) is still unknown. The present article, following a top-down approach, endeavors to study the effect of varying $m_s$ on the radiative stability of the observational parameters associated with the neutrino mixing. These parameters get additional contributions in the minimal supersymmetric model,(MSSM). A variation in $m_s$ will influence the bounds for which the Standard Model,(SM) and MSSM work and hence will account for the different radiative contributions received from both sectors respectively, while running the renormalization group equations,(RGE). The present work establishes the invariance of the self complementarity relation among the three mixing angles, ${\theta }_{13}+{\theta }_{12}\approx {\theta }_{23}$ against the radiative evolution. A similar result concerning the mass ratio, $m_2:m_1$ is also found to be valid. In addition to varying $m_s$, the work incorporates a range of different seesaw\,(SS) scales and tries to see how the latter affects the parameters.

   hep-phPRD(2018)·10 citations
7. 07*

   Lepton-flavour-violating gluonic operators: constraints from the LHC and low energy experiments

   Yi Cai🇨🇳 · Michael A. Schmidt🇦🇺 · German Valencia🇦🇺

   Effective operators provide a model-independent description of physics beyond the stan- dard model that is particularly useful given the absence of any signs of new physics at the Large Hadron Collider (LHC). We recast previous LHC analyses to set limits on lepton-flavour-violating gluonic effective operators of dimension 8 and compare our results to existing limits from low-energy precision experiments. Current LHC data constrains the scale $\Lambda$ of the effective operators to be larger than $\Lambda \gtrsim 0.5-1.6$ TeV depending on the flavour and thus provides the most stringent limit for all operators apart from parity-conserving operators of the form $GG\bar{\mu }{P}_{L,R}e$, where $\mu -e$ conversion in nuclei poses the most stringent constraint.

   hep-phJHEP(2018)·15 citations
8. 08*

   Search for excited muons at the future SPPC-based muon-proton colliders

   Abdullatif Caliskan🇹🇷

   We have investigated the production potential of the spin-1/2 excited muons, predicted by the preonic models, at the four SPPC (Super Proton-Proton Collider)-based muon-proton colliders in different center-of-mass energies. For the signal process \mu p\rightarrow\mu^{\star}X\rightarrow\mu\gamma X, the production cross-section and the decay width values of the excited muons have been calculated. The pseudorapidity and transverse momentum distributions of the final state particles of muons and photons have been obtained to be determine the kinematical cuts best suited for discovery of the excited muons. By applying these cuts we have gotten the discovery, observation and exclusion mass limits of the excited muons for two compositeness scale values. It is shown that the discovery limits on the excited muons in case the compositeness scale equals to 100 TeV are 2.7, 3.9, 3.1 and 6.7 TeV for center-of-mass energies of 10.3, 14.2, 14.6 and 20.2 TeV, respectively.

   hep-ph6 citations
9. 09*

   Complete two-loop QCD contributions to the lightest Higgs-boson mass in the MSSM with complex parameters

   Sophia Borowka🇨🇭 · Sebastian Paßehr🇫🇷 · Georg Weiglein🇩🇪

   Higher-order corrections to the MSSM Higgs-boson masses are desirable for accurate predictions currently testable at the LHC. By comparing the prediction with the measured value of the discovered Higgs signal, viable parameter regions can be inferred. For an improved theory accuracy, we compute all two-loop corrections involving the strong coupling for the Higgs-boson mass spectrum of the MSSM with complex parameters. Apart from the dependence on the strong coupling, these contributions depend on the weak coupling and Yukawa couplings, leading to terms of $\mathcal{O}\left(\alpha {\alpha }_s\right)$ and $\mathcal{O}\left(\sqrt{{\alpha }_{q_1}}\sqrt{{\alpha }_{q_2}}{\alpha }_s\right)$, ($q_{1,2}=t,b,c,s,u,d$). The full dependence on the external momentum and all relevant mass scales is taken into account. The calculation is performed in the Feynman-diagrammatic approach which is flexible in the choice of the employed renormalization scheme. For the phenomenological results presented here, a renormalization scheme consistent with higher-order corrections included in the code $\text{FeynHiggs}$ is adopted. For the evaluation of the results, a total of $513$ two-loop two-point integrals with up to five different mass scales are computed fully numerically using the program $\text{SecDec}$. A comparison with existing results in the limit of real parameters and/or vanishing external momentum is carried out, and the impact on the lightest Higgs-boson mass is discussed, including the dependence on complex phases. The new results will be included in the public code $\text{FeynHiggs}$.

   hep-phEPJC(2018)·44 citations
10. 10*

    ${ϵ}^{\prime }/ϵ$ Anomaly and Neutron EDM in $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ model with Charge Symmetry

    Naoyuki Haba🇯🇵 · Hiroyuki Umeeda🇯🇵 · Toshifumi Yamada🇯🇵

    The Standard Model prediction for ${ϵ}^{\prime }/ϵ$ based on recent lattice QCD results exhibits a tension with the experimental data. We solve this tension through $W_R^{+}$ gauge boson exchange in the $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ model with `charge symmetry', whose theoretical motivation is to attribute the chiral structure of the Standard Model to the spontaneous breaking of $SU(2{)}_R\times U(1{)}_{B-L}$ gauge group and charge symmetry. We show that $M_{W_R}<58$ TeV is required to account for the ${ϵ}^{\prime }/ϵ$ anomaly in this model. Next, we make a prediction for the neutron EDM in the same model and study a correlation between ${ϵ}^{\prime }/ϵ$ and the neutron EDM. We confirm that the model can solve the ${ϵ}^{\prime }/ϵ$ anomaly without conflicting the current bound on the neutron EDM, and further reveal that almost all parameter regions in which the ${ϵ}^{\prime }/ϵ$ anomaly is explained will be covered by future neutron EDM searches, which leads us to anticipate the discovery of the neutron EDM.

    hep-phJHEP(2018)·29 citations
11. 11*

    Stress-testing the VBF approximation in multijet final states

    Francisco Campanario🇪🇸 · Terrance M. Figy🇺🇸 · Simon Plätzer🇦🇹 · Michael Rauch🇩🇪 · Peter Schichtel🇩🇪 · Malin Sjödahl🇸🇪

    We consider electro-weak Higgs plus three jets production at NLO QCD beyond strict VBF acceptance cuts. We investigate, for the first time, how accurate the VBF approximation is in these regions and within perturbative uncertainties, by a detailed comparison of full and approximate calculations. We find that a rapidity gap between the tagging jets guarantees a good approximation, while an invariant mass cut alone is not sufficient, which needs to be confronted with experimental choices. We also find that a significant part of the QCD corrections can be attributed to Higgs-Strahlungs-type topologies.

    hep-phPRD(2018)·25 citations
12. 12*

    Neutrino masses from Planck-scale lepton number breaking

    Alejandro Ibarra🇩🇪 · Patrick Strobl🇩🇪 · Takashi Toma🇩🇪

    We consider an extension of the Standard Model by right-handed neutrinos and we argue that, under plausible assumptions, a neutrino mass of $\mathcal{O}(0.1)\mathrm{eV}$ is naturally generated by the breaking of the lepton number at the Planck scale, possibly by gravitational effects, without the necessity of introducing new mass scales in the model. Some implications of this framework are also briefly discussed.

    hep-phPRL(2019)·20 citations
13. 13*

    Estimation on the neutrino masses by using neutrino oscillation parameters

    Wen-Jie Wu🇨🇳 · Xiang Zhou🇨🇳

    It has been shown that neutrino masses can be determined under the particle ansatz. In this paper, we give the general formulas of neutrino masses related to the neutrino oscillation parameters which show that there is a mass hierarchy transition. Using the best fit values measured by electron and muon neutrino oscillation experiments, the total neutrino mass is about 0.25 eV. According to the standard neutrino cosmology, the neutrino energy density is about 55 eV/cm${}^3$ and ${\Omega }_m{h}^2>{\Omega }_{\nu }{h}^2\sim 0.0055$.

    hep-phastro-ph.CO0 citations
14. 14*

    Solving the Hierarchy Problem Discretely

    Anson Hook🇺🇸

    We present a new solution to the Hierarchy Problem utilizing non-linearly realized discrete symmetries. The cancelations occur due to a discrete symmetry that is realized as a shift symmetry on the scalar and as an exchange symmetry on the particles with which the scalar interacts. We show how this mechanism can be used to solve the Little Hierarchy Problem as well as give rise to light axions.

    hep-phhep-thPRL(2018)·177 citations
15. 15*

    A new leading contribution to neutrinoless double-beta decay

    V. Cirigliano🇺🇸 · W. Dekens🇺🇸 · J. de Vries🇳🇱 · M. L. Graesser🇺🇸 · E. Mereghetti🇺🇸 · S. Pastore🇺🇸 · U. van Kolck🇫🇷

    Within the framework of chiral effective field theory we discuss the leading contributions to the neutrinoless double-beta decay transition operator induced by light Majorana neutrinos. Based on renormalization arguments in both dimensional regularization with minimal subtraction and a coordinate-space cutoff scheme, we show the need to introduce a leading-order short-range operator, missing in all current calculations. We discuss strategies to determine the finite part of the short-range coupling by matching to lattice QCD or by relating it via chiral symmetry to isospin-breaking observables in the two-nucleon sector. Finally, we speculate on the impact of this new contribution on nuclear matrix elements of relevance to experiment.

    hep-phhep-latnucl-thPRL(2018)·209 citations
16. 16*

    Multi-peaked signatures of primordial gravitational waves from multi-step electroweak phase transition

    António P. Morais🇵🇹 · Roman Pasechnik🇸🇪 · Thibault Vieu🇵🇹

    The first-order electroweak phase transition in the early universe could occur in multiple steps leading to specific multi-peaked signatures in the primordial gravitational wave (GW) spectrum. We argue that these signatures are generic phenomena in multi-scalar extensions of the Standard Model. In a simple example of such an extension, we have studied the emergence of reoccurring and nested vacuum bubble configurations and their role in the formation of multiple peaks in the GW spectrum. The conditions for potential detectability of these features by the forthcoming generation of interferometers have been studied.

    hep-phgr-qchep-thPoS(2020)·30 citations
17. 17*

    Quantum Cosmic No-Hair Theorem and Inflation

    Nemanja Kaloper🇺🇸 · James Scargill🇺🇸

    We consider implications of the quantum extension of the inflationary no hair theorem. We show that when the quantum state of inflation is picked to ensure the validity of the EFT of fluctuations, it takes only $\mathcal{O}(10)$ efolds of inflation to erase the effects of the initial distortions on the inflationary observables. Thus the Bunch-Davies vacuum is a very strong quantum attractor during inflation. We also consider bouncing universes, where the initial conditions seem to linger much longer and the quantum `balding' by evolution appears to be less efficient.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2019)·25 citations
18. 18*

    Finite-temperature phase structure of SU(4) gauge theory with multiple fermion representations

    Venkitesh Ayyar🇺🇸 · Thomas DeGrand🇺🇸 · Daniel C. Hackett🇺🇸 · William I. Jay🇺🇸 · Ethan T. Neil🇺🇸 · Yigal Shamir🇮🇱 · Benjamin Svetitsky🇮🇱

    We investigate the phase structure of SU(4) gauge theory with the gauge field simultaneously coupled to two flavors of fermion in the fundamental representation and two flavors of fermion in the two-index antisymmetric representation. We find that the theory has only two phases, a low-temperature phase with both species of fermion confined and chirally broken, and a high-temperature phase with both species of fermion deconfined and chirally restored. The single phase transition in the theory appears to be first order, in agreement with theoretical predictions.

    ↳ hep-lathep-phPRD(2018)·56 citations
19. 19*

    Field theoretic renormalization study of interaction corrections to the universal ac conductivity of graphene

    S. Teber🇫🇷 · A. V. Kotikov🇷🇺

    The two-loop interaction correction coefficient to the universal ac conductivity of disorder-free intrinsic graphene is computed with the help of a field theoretic renormalization study using the BPHZ prescription. Non-standard Ward identities imply that divergent subgraphs (related to Fermi velocity renormalization) contribute to the renormalized optical conductivity. Proceeding either via density-density or via current-current correlation functions, a single well-defined value is obtained: $\mathcal{C}=(19-6\pi )/12)=0.01$ in agreement with the result first obtained by Mishchenko and which is compatible with experimental uncertainties.

    ↳ cond-mat.mes-hallhep-phhep-thJHEP(2018)·15 citations
20. 20*

    Multi-messenger gamma-ray counterpart of the IceCube neutrino signal

    A.Neronov🇨🇭 · M.Kachelriess🇳🇴 · D.V. Semikoz🇫🇷

    A signal of high-energy extraterrestrial neutrinos from unknown source(s) was recently discovered by the IceCube experiment. Neutrinos are always produced together with gamma-rays, but the gamma-ray flux from extragalactic sources is suppressed due to attenuation in the intergalactic medium. We report the discovery of a gamma-ray excess at high Galactic latitudes starting at energies 300 GeV in the data of the Fermi telescope. We show that the multi-TeV gamma-ray diffuse emission has spectral characteristics at both low and high Galactic latitudes compatible with those of the IceCube high neutrino signal in the same sky regions. This suggests that these gamma-rays are the counterpart of the IceCube neutrino signal, implying that a sizable part of the IceCube neutrino flux originates from the Milky Way. We argue that the diffuse neutrino and gamma-ray signal at high Galactic latitudes originates either from previously unknown nearby cosmic ray "PeVatron" source(s), an extended Galactic CR halo or from decays of heavy dark matter particles.

    ↳ astro-ph.HEhep-phPRD(2018)·49 citations
21. 21*

    Insights on Dark Matter from Hydrogen during Cosmic Dawn

    Julian B. Muñoz🇺🇸 · Abraham Loeb🇺🇸

    The origin and composition of the cosmological dark matter remain a mystery. However, upcoming 21-cm measurements during cosmic dawn, the period of the first stellar formation, can provide new clues on the nature of dark matter. During this era, the baryon-dark matter fluid is the slowest it will ever be, making it ideal to search for dark matter elastically scattering with baryons through massless mediators, such as the photon. Here we explore whether dark-matter particles with an electric "minicharge" can significantly alter the baryonic temperature and, thus, affect 21-cm observations. We find that the entirety of the dark matter cannot be minicharged at a significant level, lest it interferes with Galactic and extragalactic magnetic fields. However, if minicharged particles comprise a subpercent fraction of the dark matter, and have charges $ϵ\sim 10^{-6}$---in units of the electron charge---and masses $m_{\chi }\sim 1-60$ MeV, they can significantly cool down the baryonic fluid, and be discovered in 21-cm experiments. We show how this scenario can explain the recent result by the EDGES collaboration, which requires a lower baryonic temperature than possible within the standard model, while remaining consistent with all current observations.

    ↳ astro-ph.COhep-phNature(2018)·353 citations
22. 22*

    The Bright and Choked Gamma-Ray Burst Contribution to the IceCube and ANTARES Low-Energy Excess

    Peter B. Denton🇩🇰 · Irene Tamborra🇩🇰

    The increasing statistics of the high-energy neutrino flux observed by the IceCube Observatory points towards an excess of events above the atmospheric neutrino background in the 30--400 TeV energy range. Such an excess is compatible with the findings of the ANTARES Telescope and it would naturally imply the possibility that more than one source class contributes to the observed flux. Electromagnetically hidden sources have been invoked to interpret this excess of events at low energies. By adopting a unified model for the electromagnetically bright and choked gamma-ray bursts and taking into account particle acceleration at the internal and collimation shock radii, we discuss whether bright and choked bursts are viable candidates. Our findings suggest that, although producing a copious neutrino flux, choked and bright astrophysical jets cannot be the dominant sources of the excess of neutrino events. A fine tuning of the model parameters or distinct scenarios for choked jets should be invoked in order to explain the low-energy neutrino data of IceCube and ANTARES.

    ↳ astro-ph.HEhep-phJCAP(2018)·25 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.