Thu·Jun 21, 2018Thursday·June 21, 2018

1. 01*

   Mu-tau reflection symmetry with a high scale texture-zero

   C. C. Nishi🇧🇷 · B. L. Sánchez-Vega🇧🇷 · G. Souza Silva🇧🇷

   The $\mu \tau$-reflection symmetric neutrino mass matrix can accommodate all known neutrino mixing angles, with maximal atmospheric angle fixed, and predicts all the unknown CP phases of the lepton sector but is unable to predict the absolute neutrino mass scale. Here we present a highly predictive scenario where $\mu \tau$-reflection is combined with a discrete abelian symmetry to enforce a texture-zero in the mass matrix of the heavy right-handed neutrinos that generate the light neutrino masses. Such a restriction reduces the free parameters of the low energy theory to zero and the absolute neutrino mass scale is restricted to few discrete regions, three in the few meV range and one extending up to around 30 meV. The heavy neutrino sector is dependent only on two free parameters which are further restricted to small regions from the requirement of successful leptogenesis. Mass degenerate heavy neutrinos are possible in one case but there is no resonant enhancement of the CP asymmetry.

   hep-phJHEP(2018)·29 citations
2. 02*

   COHERENT analysis of neutrino generalized interactions

   D. Aristizabal Sierra🇨🇱 · Valentina De Romeri🇪🇸 · N. Rojas🇨🇱

   Effective neutrino-quark generalized interactions are entirely determined by Lorentz invariance, so they include all possible four-fermion non derivative Lorentz structures. They contain neutrino-quark non-standard interactions as a subset, but span over a larger set that involves effective scalar, pseudoscalar, axial and tensor operators. Using recent COHERENT data, we derive constraints on the corresponding couplings by considering scalar, vector and tensor quark currents and assuming no lepton flavor dependence. We allow for mixed neutrino-quark Lorentz couplings and consider two types of scenarios in which: (i) one interaction at the nuclear level is present at a time, (ii) two interactions are simultaneously present. For scenarios (i) our findings show that scalar interactions are the most severely constrained, in particular for pseudoscalar-scalar neutrino-quark couplings. In contrast, tensor and non-standard vector interactions still enable for sizable effective parameters. We find as well that an extra vector interaction improves the data fit when compared with the result derived assuming only the standard model contribution. In scenarios (ii) the presence of two interactions relaxes the bounds and opens regions in parameter space that are otherwise closed, with the effect being more pronounced in the scalar-vector and scalar-tensor cases. We point out that barring the vector case, our results represent the most stringent bounds on effective neutrino-quark generalized interactions for mediator masses of order $\sim 1$GeV. They hold as well for larger mediator masses, case in which they should be compared with limits from neutrino deep-inelastic scattering data.

   hep-phhep-exPRD(2018)·179 citations
3. 03*

   Dilepton azimuthal correlations in $t\bar{t}$ production

   J.A. Aguilar-Saavedra🇪🇸

   The dilepton azimuthal correlation, namely the difference $\varphi$ between the azimuthal angles of the positive and negative charged lepton in the laboratory frame, provides a stringent test of the spin correlation in $t\bar{t}$ production at the Large Hadron Collider. We introduce a parameterisation of the differential cross section $d\sigma /d\varphi$ in terms of a Fourier series and show that the third-order expansion provides a sufficiently accurate approximation. This expansion can be considered as a `bridge' between theory and data, making it very simple to cast predictions in the Standard Model (SM) and beyond, and to report measurements, without the need to provide the numbers for the whole binned distribution. We show its application by giving predictions for the coefficients in the presence of (i) an anomalous top chromomagnetic dipole moment; (ii) an anomalous $tbW$ interaction. The methods presented greatly facilitate the study of this angular distribution, which is of special interest given the $3.2(3.7)\sigma$ deviation from the SM next-to-leading order prediction found by the ATLAS Collaboration in Run 2 data.

   hep-phhep-exJHEP(2018)·11 citations
4. 04*

   Parton distributions from nonlocal chiral SU(3) effective theory. I. Splitting functions

   Y. Salamu🇨🇳 · Chueng-Ryong Ji🇺🇸 · W. Melnitchouk🇺🇸 · A. W. Thomas🇦🇺 · P. Wang🇨🇳

   We present a new formulation of pseudoscalar meson loop corrections to nucleon parton distributions within a nonlocal covariant chiral effective field theory, including contributions from SU(3) octet and decuplet baryons. The nonlocal Lagrangian, constrained by requirements of local gauge invariance and Lorentz-invariant ultraviolet regularization, generates additional interactions associated with gauge links. We use these to compute the full set of proton $\to$ meson + baryon splitting functions, which in general contain on-shell and off-shell contributions, in addition to $\delta$-function terms at zero momentum, along with nonlocal contributions associated with the finite size of the proton. We illustrate the shapes of the various local and nonlocal functions numerically using a simple example of a dipole regulator.

   hep-phnucl-thPRD(2019)·30 citations
5. 05*

   Shear viscosity of ultrarelativistic Boson systems in the presence of a Bose-Einstein condensate

   Zhengyu Chen🇨🇳 · Carsten Greiner🇩🇪 · Zhe Xu🇨🇳 · Pengfei Zhuang🇨🇳

   We calculate for the first time the shear viscosity of ultrarelativistic Boson systems in the presence of a Bose-Einstein condensate (BEC). Two different methods are used. One is the Grad's method of moments and another is the Green-Kubo relation within a kinetic transport approach. In this work we consider a Boson system with isotropic elastic collisions and a gluon system with elastic scatterings described by perturbation QCD (pQCD). The results show that the presence of a BEC lowers the shear viscosity. This effect becomes stronger for the increasing proportion of the BEC in the Boson system and is insensitive to the detail of interactions.

   hep-phnucl-thPRC(2019)·6 citations
6. 06*

   Proton shape fluctuations and its relation to DIS

   Heikki Mäntysaari🇫🇮

   We review the recent progress in extracting the proton fluctuating substructure by studying exclusive processes at HERA, and the applications of these developments in the interpretation of the LHC heavy ion data. The possibilities to extract the proton geometry directly from the LHC high-multiplicity proton-nucleus and proton-proton collision data is also discussed.

   hep-phnucl-thPoS(2018)·0 citations
7. 07*

   Next-to-Leading Order QCD Corrections to Inclusive Heavy-Flavor Production in Polarized Deep-Inelastic Scattering

   Felix Hekhorn🇩🇪 · Marco Stratmann🇩🇪

   We report on a recently completed, first calculation of the full next-to-leading order QCD corrections for heavy flavor contributions to the inclusive structure function $g_1$ in longitudinally polarized deep-inelastic scattering. All results are derived with largely analytical methods and retain the full dependence on the heavy quark's mass. As a first phenomenological application, inclusive charm production at a future electron-ion collider and its sensitivity to the polarized gluon distribution is studied. Theoretical uncertainties due to the residual dependence on unphysical factorization and renormalization scales are estimated.

   hep-phPoS(2018)·2 citations
8. 08*

   Neutrino phenomenology from leptogenesis

   Franco Buccella🇮🇹 · Damiano F. G. Fiorillo🇮🇹 · Gennaro Miele🇮🇹 · Stefano Morisi🇮🇹 · Ofelia Pisanti🇮🇹 · Pietro Santorelli🇮🇹

   Assuming a type-I seesaw mechanism for neutrino mass generation and invoking a baryogengesis via leptogenesis scenario, we consider a reasonable hierarchical structure for Dirac neutrino mass matrix, similar to up-type quark mass matrix. These hypotheses imply a relevant connection between high scale CP violation and low energy one. By requiring a compact heavy neutrino mass spectrum, which allows to circumvent Davidson-Ibarra limit, one can obtain an efficient leptogenesis restricting the allowed region for low energy neutrino parameters. Once the oscillating parameters are taken inside a $3\sigma$ range, through the numerical resolution of the leptogenesis Boltzmann equations one gets the following allowed intervals for the lightest neutrino mass and the Dirac CP phase: $-0.90\pi <\delta <-0.75\pi$ and $m_1\sim (0.002-0.004)$ eV.

   hep-phEPJC(2018)·2 citations
9. 09*

   Disentangling genuine from matter-induced CP violation in neutrino oscillations

   J. Bernabeu🇪🇸 · A. Segarra🇪🇸

   We prove that, in any flavor transition, neutrino oscillation CP violating asymmetries in matter have two disentangled components: i) a CPT-odd T-invariant term, non-vanishing iff there are interactions with matter; ii) a T-odd CPT-invariant term, non-vanishing iff there is genuine CP violation. As function of the baseline, these two terms are distinct L-even and L-odd observables to separately test (i) matter effects sensitive to the neutrino hierarchy and (ii) genuine CP violation in the neutrino sector. For the golden ${\nu }_{\mu }\to {\nu }_e$ channel, the different energy distributions of the two components provide a signature of their separation. At long baselines, they show oscillations in the low energy region, with zeros at different positions and peculiar behavior around the zeros. We discover a magic energy $E=(0.91\pm 0.01)$ GeV at L = 1300 km with vanishing CPT-odd term and maximal genuine CP asymmetry proportional to $\sin \delta$, with $\delta$ the weak CP phase. For energies above 1.5 GeV, the sign of the CP asymmetry discriminates the neutrino hierarchy.

   hep-phPRL(2018)·17 citations
10. 10*

    Hadronic decays of a light Higgs-like scalar

    Alexander Monin🇨🇭 · Alexey Boyarsky🇳🇱 · Oleg Ruchayskiy🇩🇰

    We revisit the question of hadronic decays of a GeV-mass Higgs-like scalar. A number of extensions of the Standard Model predict Higgs sector with additional light scalars. Currently operating and planned Intensity Frontier experiments will probe for the existence of such particles, while theoretical computations are plagued by uncer- tainties. The goal of this paper is to bring the results in a consolidated form that can be readily used by experimental groups. To this end we provide a physically motivated fitting ansatz for the decay width that reproduces the previous non-perturbative nu- merical analysis. We describe systematic uncertainties of the non-perturbative method and provide explicit examples of the influence of extra resonances above 1.4 GeV onto the total decay width.

    hep-phPRD(2019)·35 citations
11. 11*

    Calculation of the pion-photon transition form factor using dispersion relations and renormalization-group summation

    C. Ayala🇨🇱 · S. V. Mikhailov🇷🇺 · N. G. Stefanis🇩🇪

    We consider the lightcone sum-rule description of the pion-photon transition form factor, based on dispersion relations, in combination with the renormalization group of QCD, in terms of the formal solution of the Efremov-Radyushkin-Brodsky-Lepage evolution equation, and show that the emerging scheme amounts to a certain version of Fractional Analytic Perturbation Theory (FAPT). In order to ensure the correct asymptotic behavior of the considered physical quantity, this modified FAPT version has to be supplemented by process-specific boundary conditions---in contrast to the standard one. However, it provides the advantage of significantly improving the inclusion of radiative corrections in the low-momentum regime of QCD perturbation theory using renormalization-group summation.

    hep-phPRD(2018)·14 citations
12. 12*

    There Is No Proof of Thermalized Quark-Gluon Plasma at RHIC and LHC

    Gouranga C Nayak🇺🇸

    Although Tevatron has discovered top quark and LHC (pp collisions) has discovered Higgs boson but the RHIC and LHC heavy-ion colliders have not discovered thermalized quark-gluon plasma (QGP). This is because the experimental data of top quark at Tevatron and the experimental data of Higgs boson at LHC are compared with the exact first principle calculation but the experimental data at RHIC and LHC are compared with simplistic models and assumptions which are not exact first principle calculation. In this paper we show that the exact first principle method to study quark-gluon plasma at RHIC and LHC is the nonequilibrium-nonperturbative QCD by using closed-time path integral formalism. Hence in the absence of such exact first principle calculation we conclude that there is no proof of thermalized quark-gluon plasma at RHIC and LHC.

    hep-phhep-exhep-latnucl-ex+10 citations
13. 13*

    Leptonic WIMP Coannihilation and the Current Dark Matter Search Strategy

    Michael J. Baker🇨🇭 · Andrea Thamm🇨🇭

    We discuss the extent to which models of Weakly Interacting Massive Particle (WIMP) Dark Matter (DM) at and above the electroweak scale can be probed conclusively in future high energy and astroparticle physics experiments. We consider simplified models with bino-like dark matter and slepton-like coannihilation partners, and find that perturbative models yield the observed relic abundance up to at least 10 TeV. We emphasise that coannihilation can either increase or decrease the dark matter relic abundance. We compute the sensitivity of direct detection experiments to DM-nucleus scattering, consider indirect detection bounds and estimate the sensitivity of future proton colliders to slepton pair production. We find that current and future experiments will be able to probe the Dirac DM models up to at least 10 TeV. However, current and future searches will not be sensitive to models of Majorana dark matter for masses above 2 or 4 TeV, for one or ten coannihilation partners respectively, leaving around 70 % of the parameter space unconstrained. This demonstrates the need for new experimental ideas to access models of coannihilating Majorana dark matter.

    hep-phJHEP(2018)·36 citations
14. 14*

    Impact of an extra gauge interaction on naturalness of supersymmetry

    Marcin Badziak🇵🇱 · Keisuke Harigaya🇺🇸

    It is pointed out that in supersymmetric models with a new gauge symmetry under which the Higgs is charged, the fine-tuning of the electroweak symmetry breaking is relaxed due to suppression of the top Yukawa coupling at higher scales by a new large gauge coupling. We calculate the fine-tuning in an explicit model and find that the lower bounds on stops and gluino masses from the naturalness criterion are increased by several hundred GeV in comparison to the Minimal Supersymmetric Standard Model (MSSM). The fine-tuning is improved by one to two orders of magnitude as compared to the MSSM, as a consequence of both the suppression of the top Yukawa coupling and the additional tree-level contribution to the Higgs mass allowing for much lighter stops.

    hep-phJHEP(2018)·2 citations
15. 15*

    Model independent Analysis of Dirac CP Violating Phase for some well known mixing scenarios

    Sumit K. Garg🇮🇳

    We present a model-independent analysis of Leptonic CP violation for some well known mixing scenarios. In particular, we considered modified schemes for Bimaximal(BM), Democratic(DC), Hexagonal(HG) and Tribimaixmal(TBM) mixing for our numerical investigation. These model-independent corrections to mixing matrices are parameterized in terms of complex rotation matrices ($U$) with related modified PMNS matrix of the forms \big($U_{ij}^l\cdot V_M,V_M\cdot U_{ij}^r$ \big ) where $U_{ij}^{l,r}$ is complex rotation in ij sector and $V_M$ is unperturbed mixing scheme. We present generic formulae for mixing angles, Dirac CP phase(${\delta }_{CP}$) and Jarkslog Invariant($J_{CP}$) in terms of correction parameters. The parameter space of each modified mixing case is scanned for fitting neutrino mixing angles using ${\chi }^2$ approach and the corresponding predictions for Leptonic CP Phase(${\delta }_{CP}$) and Jarkslog Invariant($J_{CP}$) has been evaluated from allowed parameter space. The obtained ranges are reported for all viable cases.

    hep-phInt.J.Mod.Phys.A(2021)·10 citations
16. 16*

    Master integrals for the NNLO virtual corrections to $\mu e$ scattering in QED: the non-planar graphs

    Stefano Di Vita🇮🇹 · Stefano Laporta🇮🇹 · Pierpaolo Mastrolia🇮🇹 · Amedeo Primo🇨🇭 · Ulrich Schubert🇺🇸

    We evaluate the master integrals for the two-loop non-planar box-diagrams contributing to the elastic scattering of muons and electrons at next-to-next-to-leading order in QED. We adopt the method of differential equations and the Magnus exponential to determine a canonical set of integrals, finally expressed as a Taylor series around four space-time dimensions, with coefficients written as a combination of generalised polylogarithms. The electron is treated as massless, while we retain full dependence on the muon mass. The considered integrals are also relevant for crossing-related processes, such as di-muon production at $e^{+}{e}^{-}$ colliders, as well as for the QCD corrections to top-pair production at hadron colliders. In particular, our results, together with the planar master integrals recently computed, represent the complete set of functions needed for the evaluation of the photonic two-loop virtual next-to-next-to-leading order QED corrections to $\mu e\to \mu e$ and $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$.

    hep-phhep-thJHEP(2018)·91 citations
17. 17*

    The cosmological impact of future constraints on $H_0$ from gravitational-wave standard sirens

    Eleonora Di Valentino🇬🇧 · Daniel E. Holz🇺🇸 · Alessandro Melchiorri🇮🇹 · Fabrizio Renzi🇮🇹

    Gravitational-wave standard sirens present a novel approach for the determination of the Hubble constant. After the recent spectacular confirmation of the method thanks to GW170817 and its optical counterpart, additional standard siren measurements from future gravitational-wave sources are expected to constrain the Hubble constant to high accuracy. At the same time, improved constraints are expected from observations of cosmic microwave background (CMB) polarization and from baryon acoustic oscillations (BAO) surveys. We explore the role of future standard siren constraints on $H_0$ in light of expected CMB+BAO data. Considering a $10$-parameters cosmological model, in which curvature, the dark energy equation of state, and the Hubble constant are unbounded by CMB observations, we find that a combination of future CMB+BAO data will constrain the Hubble parameter to $\sim 1.5\%$. Further extending the parameter space to a time-varying dark energy equation of state, we find that future CMB+BAO constraints on $H_0$ are relaxed to $\sim 3.0\%$. These accuracies are within reach of future standard siren measurements from the Hanford-Livingston-Virgo and the Hanford-Livingston-Virgo-Japan-India networks of interferometers, showing the cosmological relevance of these sources. If future gravitational-wave standard siren measurements reach $1\%$ on $H_0$, as expected, they would significantly improve future CMB+BAO constraints on curvature and on the dark energy equation of state by up to a factor $\sim 3$. We also show that the inclusion of $H_0$ constraints from gravitational-wave standard sirens could result in a reduction of the dark energy figure-of-merit (i.e., the cosmological parameter volume) by up to a factor of $\sim 400$.

    ↳ astro-ph.COgr-qchep-phPRD(2018)·48 citations
18. 18*

    Non-Abelian Anomalous (Super)Fluids in Thermal Equilibrium from Differential Geometry

    Juan L. Mañes🇪🇸 · Eugenio Megias🇪🇸 · Manuel Valle🇪🇸 · Miguel A. Vazquez-Mozo🇪🇸

    We apply differential geometry methods to the computation of the anomaly-induced hydrodynamic equilibrium partition function. Implementing the imaginary-time prescription on the Chern-Simons effective action on a stationary background, we obtain general closed expressions for both the invariant and anomalous part of the partition function. This is applied to the Wess-Zumino-Witten action for Goldstone modes, giving the equilibrium partition function of superfluids. In all cases, we also study the anomaly-induced gauge currents and energy-momentum tensor, providing explicit expressions for them.

    ↳ hep-thcond-mat.str-elhep-phJHEP(2018)·18 citations
19. 19*

    Constraining late-time transitions in the dark energy equation of state

    C. J. A. P. Martins🇵🇹 · M. Prat Colomer🇪🇸

    One of the most compelling goals of observational cosmology is the characterisation of the properties of the dark energy component thought to be responsible for the recent acceleration of the universe, including its possible dynamics. In this work we study phenomenological but physically motivated classes of models in which the dark energy equation of state can undergo a rapid transition at low redshifts, perhaps associated with the onset of the acceleration phase itself. Through a standard statistical analysis we have used low-redshift cosmological data, coming from Type Ia supernova and Hubble parameter measurements, to set constraints on the steepness of these possible transitions as well as on the present-day values of the dark energy equation of state and in the asymptotic past in these models. We have also studied the way in which these constraints depend on the specific parametrisation being used. Our results confirm that such late-time transitions are strongly constrained. If one demands a matter-like pre-transition behaviour, then the transition is constrained to occur at high redshifts (effectively in the matter era), while if the pre-transition equation of state is a free parameter then it is constrained to be close to that of a cosmological constant. In any case, the value of dark energy equation of state near the present day must also be very similar to that of a cosmological constant. The overall conclusion is that any significant deviations from this behaviour can only occur in the deep matter era, so there is no evidence for a transition associated with the onset of acceleration. Observational tools capable of probing the dynamics of the universe in the deep matter era are therefore particularly important.

    ↳ astro-ph.COgr-qchep-phAstron.Astrophys.(2018)·8 citations
20. 20*

    Beyond subhalos: Probing the collective effect of the Universe's small-scale structure with gravitational lensing

    Francis-Yan Cyr-Racine🇺🇸 · Charles R. Keeton🇺🇸 · Leonidas A. Moustakas🇺🇸

    Gravitational lensing has emerged as a powerful probe of the matter distribution on subgalactic scales, which itself may contain important clues about the fundamental origins and properties of dark matter. Broadly speaking, two different approaches have been taken in the literature to map the small-scale structure of the Universe using strong lensing, with one focused on measuring the position and mass of a small number of discrete massive subhalos appearing close in projection to lensed images, and the other focused on detecting the collective effect of all the small-scale structure between the lensed source and the observer. In this paper, we follow the latter approach and perform a detailed study of the sensitivity of galaxy-scale gravitational lenses to the ensemble properties of small-scale structure. As in some previous studies, we adopt the language of the substructure power spectrum to characterize the statistical properties of the small-scale density field. We present a comprehensive theory that treats lenses with extended sources as well as those with time-dependent compact sources (such as quasars) in a unified framework for the first time. Our approach uses mode functions to provide both computational advantages and insights about couplings between the lens and source. The goal of this paper is to develop the theory and gain the intuition necessary to understand how the sensitivity to the substructure power spectrum depends on the source and lens properties, with the eventual aim of identifying the most promising targets for such studies.

    ↳ astro-ph.COhep-phPRD(2019)·51 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.