Wed·Nov 29, 2017Wednesday·November 29, 2017

1. 01*

   The radiative decay $D^0\to {\bar{K}}^{\ast 0}\gamma$ with vector meson dominance

   J. M. Dias🇪🇸 · V. R. Debastiani🇪🇸 · Ju-Jun Xie🇨🇳 · E. Oset🇪🇸

   Motivated by the experimental measurements of $D^0$ radiative decay modes we have proposed a model to study the $D^0\to {\bar{K}}^{\ast 0}\gamma$ decay, by establishing a link with $D^0\to {\bar{K}}^{\ast 0}V$ $(V={\rho }^0,\omega )$ decays through the vector meson dominance hypothesis. In order to do this properly, we have used the Lagrangians from the local hidden gauge symmetry approach to account for $V\gamma$ conversion. As a result, we have found the branching ratio $\mathcal{B}[D^0\to {\bar{K}}^{\ast 0}\gamma ]=(1.55-3.44)\times 10^{-4}$, which is in fair agreement with the experimental values reported by Belle and Babar collaborations.

   hep-phCPC(2018)·6 citations
2. 02*

   Double distributions and generalized parton distributions from the parton number conserved light front wave function overlap representation

   Dieter Müller🇭🇷

   We show that Mellin moments of generalized parton distributions, given as even polynomials in the skewness parameter, are obtained from the Taylor expansion of light front wave functions. Furthermore, we derive non-standard versions of the inverse Radon transform to obtain the double distribution from the parton number conserved light front wave function overlap. These transformations are utilized to extend a generalized parton distribution from the outer region to the central one. We exemplify the formalism for a light front wave function that arises from an AdS/QCD duality conjecture.

   hep-ph7 citations
3. 03*

   Comment on `Nucleon Structure Functions from Operator Product Expansion on the Lattice'

   Keh-Fei Liu🇺🇸

   It is suggested in the paper by A.J. Chambers {\it et al.} (Phys. Rev. Lett. 118, 242001 (2017), arXiv:1703.01153) that the time-ordered current-curent correlator in the nucleon calculated on the lattice is to be identified as the forward Compton amplitude so that it is related to the sum of the even moments of the structure function as in the Minkowski space in the continuum. We point out two problems with this identification. First of all, the current-current correlator defined in the Euclidean space is not analytic everywhere on the rest of the complex $\nu$ or $\omega$ plane, besides the cuts on the real axis. As such, there is no dispersion relation to relate it to its imaginary part and hence the moments of the structure function. On the lattice, there is an additional difficulty in that the higher dimensional local operators from the operator production expansion (OPE) of the current-current product can mix with lower dimensional higher-twist operators which leads to divergences in the powers of inverse lattice spacing. This mixing needs to be removed before their matrix elements can be identified as the moments of the structure function.

   hep-phhep-latnucl-th0 citations
4. 04*

   The NNLO QCD soft function for 1-jettiness

   John M. Campbell🇺🇸 · R. Keith Ellis🇬🇧 · Roberto Mondini🇺🇸 · Ciaran Williams🇺🇸

   We calculate the soft function for the global event variable 1-jettiness at next-to-next-to-leading order (NNLO) in QCD. We focus specifically on the non-Abelian contribution, which, unlike the Abelian part, is not determined by the next-to-leading order result. The calculation uses the known general forms for the emission of one and two soft partons and is performed using a sector-decomposition method that is spelled out in detail. Results are presented in the form of numerical fits to the 1-jettiness soft function for LHC kinematics (as a function of the angle between the incoming beams and the final-state jet) and for generic kinematics (as a function of three independent angles). These fits represent one of the needed ingredients for NNLO calculations that use the N-jettiness event variable to handle infrared singularities.

   hep-phEPJC(2018)·41 citations
5. 05*

   Minimisation strategies for the determination of parton density functions

   Stefano Carrazza🇨🇭 · Nathan P. Hartland🇳🇱

   We discuss the current minimisation strategies adopted by research projects involving the determination of parton distribution functions (PDFs) and fragmentation functions (FFs) through the training of neural networks. We present a short overview of a proton PDF determination obtained using the covariance matrix adaptation evolution strategy (CMA-ES) optimisation algorithm. We perform comparisons between the CMA-ES and the standard nodal genetic algorithm (NGA) adopted by the NNPDF collaboration.

   hep-phJ.Phys.Conf.Ser.(2018)·6 citations
6. 06*

   Bottom and Charm Quark Mass Determination from Quarkonium at N${}^3$LO

   Pablo G. Ortega🇪🇸 · Vicent Mateu🇪🇸

   The non-perturbative nature of QCD at hadronic scales implied the development of phenomenological approaches such as quark models or, more recently, computer-based calculations using Lattice QCD. However, the unique properties of heavy quarkonium systems allow an entire calculation in terms of non-relativistic perturbative QCD. In this work, the bottomonium spectrum, up to $n=3$, and the ground state charmonium states, are analyzed in the framework of Non-Relativistic Quantum Chromodynamics at N${}^3$LO. For bottomonium, finite charm quark mass effects in the QCD potential and the $\overline{MS}$-pole mass relation are incorporated to the highest known order, $\mathcal{O}({\epsilon }^3)$ in the ${\rm Y}$-scheme counting. The bottom quark pole mass is expressed in terms of the MSR mass, a low-scale short-distance mass which cancels the $u=1/2$ renormalon of the static potential. We study the $n_{\ell }=3$ and $n_{\ell }=4$ schemes, finding a negligible difference between the two if finite $m_c$ effects are smoothly incorporated in the MSR mass definition. We find that bottomonium $n=3$ states are not well behaved within perturbative NRQCD. Hence, fitting to the $n=1,2$ $b\bar{b}$ states we obtain ${\overline{m}}_b({\overline{m}}_b)=4.216\pm 0.039$ GeV. Similarly, from the lowest lying charmonium states we find ${\overline{m}}_c({\overline{m}}_c)=1.273\pm 0.054$ GeV.

   hep-phPoS(2018)·2 citations
7. 07*

   Renormalization group equation for Tsallis statistics

   Airton Deppman🇧🇷

   The non extensive statistics proposed by C. Tsallis has found wide applicability, being present even in the description of experimental data from high energy collisions. A system with a fractal structure in its energy-momentum space, named thermofractal, was shown to be described thermodynamically by the non extensive statistics. Due to the many common features between thermofractals and Hagedorn's fireballs, this system offers the possibility to investigate the origins of non extensivity in hadronic physics and in QCD. In this regard, the investigation of the scaling properties of thermofractals through the renormalization group equation, known as Callan-Symanzik equation, can be an interesting approach.

   hep-phAdv.High Energy Phys.(2018)·6 citations
8. 08*

   The Top Quark: Past, Present, and Future

   R. Sekhar Chivukula🇺🇸

   In this talk I discuss the widespread impact of the top quark on phenomena in elementary particle physics as codified through the Standard Model (SM), its important role in motivating the possiblity of physics beyond the Standard Model (BSM), and its use as a signal for detailed studies of the SM and searches for BSM physics.

   hep-phhep-exhep-th1 citation
9. 09*

   3D structure of hadrons by generalized distribution amplitudes and gravitational form factors

   S. Kumano🇯🇵 · Qin-Tao Song🇯🇵 · O. V. Teryaev🇷🇺

   Generalized distribution amplitudes (GDAs) are one type of three-dimensional structure functions, and they are related to the generalized distribution functions (GPDs) by the $s$-$t$ crossing of the Mandelstam variables. The GDA studies provide information on three-dimensional tomography of hadrons. The GDAs can be investigated by the two-photon process ${\gamma }^{\ast }\gamma \to h\bar{h}$, and the GPDs are studied by the deeply virtual Compton scattering ${\gamma }^{\ast }h\to \gamma h$. The GDA studies had been pure theoretical topics, although the GPDs have been experimentally investigated, because there was no available experimental measurement. Recently, the Belle collaboration reported their measurements on the ${\gamma }^{\ast }\gamma \to {\pi }^0{\pi }^0$ differential cross section, so that it became possible to find the GDAs from their measurements. Here, we report our analysis of the Belle data for determining the pion GDAs. From the GDAs, the timelike gravitational form factors ${\Theta }_1(s)$ and ${\Theta }_2(s)$ can be calculated, which are mechanical (pressure, shear force) and mass (energy) form factors, respectively. They are converted to the spacelike form factors by using the dispersion relation, and then gravitational radii are evaluated for the pion. The mass and mechanical radii are obtained from ${\Theta }_2$ and ${\Theta }_1$ as $\sqrt{⟨r^2{⟩}_{\text{mass}}}=0.56\sim 0.69$ fm and $\sqrt{⟨r^2{⟩}_{\text{mech}}}=1.45\sim 1.56$ fm, whereas the experimental charge radius is $\sqrt{⟨r^2{⟩}_{\text{charge}}}=0.672\pm 0.008$ fm for the charged pion. Future developments are expected in this new field to explore gravitational physics in the quark and gluon level.

   hep-phhep-exhep-latnucl-thPoS(2018)·0 citations
10. 10*

    Effective Field Theory of Majorana Dark Matter

    Huayong Han🇨🇳 · Hongyan Wu🇨🇳 · Sibo Zheng🇨🇳

    We revisit thermal Majorana dark matter from the viewpoint of minimal effective field theory. In this framework, analytic results for dark matter annihilation into standard model particles are derived. The dark matter parameter space subject to the latest LUX, PandaX-II and Xenon-1T limits is presented in a model-independent way. Applications to singlet-doublet and MSSM are presented.

    hep-phastro-ph.COhep-exCPC(2019)·8 citations
11. 11*

    Does $X(3872)$ count?

    Pablo G. Ortega🇪🇸 · Enrique Ruiz Arriola🇪🇸

    The question on whether or not weakly bound states should be effectively incorporated in a hadronic representation of the QCD partition function is addressed by analyzing the example of the $X(3872)$, a resonance close to the $D{\bar{D}}^{\ast }$ threshold which has been suggested as an example of a loosely bound molecule. This can be decided by studying the $D{\bar{D}}^{\ast }$ scattering phase-shifts in the $J^{PC}=1^{++}$ channel and their contribution to the level density in the continuum, which also gives information on its abundance in a hot medium. In this work, it is shown that, in a purely molecular picture, the bound state contribution cancels the continuum, resulting in a null occupation number density at finite temperature, which implies the $X(3872)$ does not count below the Quark-Gluon Plasma crossover ($T\sim 150$MeV). However, if a non-zero $c\bar{c}$ component is present in the $X(3872)$ wave function such cancellation does not occur for temperatures above $T\gtrsim 250$MeV.

    hep-phPoS(2018)·4 citations
12. 12*

    Naturalness and Dark Matter in a Realistic Intersecting D6-Brane Model

    Waqas Ahmed🇨🇳 · Lorenzo Calibbi🇨🇳 · Tianjun Li🇨🇳 · Shabbar Raza🇨🇳 · Jia-Shu Niu🇨🇳 · Xiao-Chuan Wang🇨🇳

    We revisit a three-family Pati-Salam model with a realistic phenomenology from intersecting D6-branes in Type IIA string theory compactified on a ${\mathbf{T}}^6/({\mathbb{Z}}_2\times {\mathbb{Z}}_2)$ orientifold, and study its naturalness in view of the current LHC and dark matter searches. We discuss spectrum and phenomenological features of this scenario demanding fine tuning better than 1\%. This requirement restricts the lightest neutralino to have mass less than about 600 GeV. We observe that the viable parameter space is tightly constrained by the requirements of naturalness and consistency with the observed dark matter relic density, so that it is fully testable at current and future dark matter searches, unless a non-thermal production mechanism of dark matter is at work. We find that $Z$-resonance, $h$-resonance, $A$-funnel and light stau/stop-neutralino coannihilation solutions are consistent with current LHC and dark matter constraints while the "well-tempered" neutralino scenario is ruled out in our model. Moreover, we observe that only Bino, Higgsinos, right-handed staus and stops can have mass below 1 TeV.

    hep-phJHEP(2018)·6 citations
13. 13*

    Weak decays of doubly heavy baryons: "decay constants"

    Xiao-Hui Hu🇨🇳 · Yue-Long Shen🇨🇳 · Wei Wang🇨🇳 · Zhen-Xing Zhao🇨🇳

    Inspired by the recent observation of the ${\Xi }_{cc}^{++}$ by LHCb collaboration, we explore the "decay constants" of doubly heavy baryons in the framework of QCD sum rules. With the ${\Xi }_{cc},{\Xi }_{bc},{\Xi }_{bb}$, and ${\Omega }_{cc},{\Omega }_{bc},{\Omega }_{bb}$ baryons interpolated by three-quark operators, we calculate the correlation functions using the operator product expansion and include the contribution from operators up to dimension six. On the hadron side, we consider both contributions from the lowest-lying states with $J^P=1/2^{+}$ and from negative parity baryons with $J^P=1/2^{-}$. We find that the results are stable and the contaminations from negative parity baryons are not severe. These results are ingredients for the QCD study of weak decays and other properties of doubly-heavy baryons.

    hep-phhep-exCPC(2018)·55 citations
14. 14*

    Resonant production of Wh and Zh at the LHC

    Antonio Dobado🇪🇸 · Felipe J. Llanes-Estrada🇪🇸 · Juan J. Sanz-Cillero🇪🇸

    We examine the production of Wh and Zh pairs at the LHC in the context of a Strongly Interacting Symmetry Breaking Sector of the Standard Model. Our description is based on a non-linear Higgs Effective Theory, including only the Standard Model particles. We focus on its scalar sector (Higgs boson h and electroweak Goldstones associated to $W_L^{\pm }$ and $Z_L$), which is expected to give the strongest beyond Standard Model rescattering effects. The range of the effective theory is extended with dispersion-relation based unitarization, and compared to the alternative extension with explicit axial-vector resonances. We estimate the Wh and Zh production cross-section, where an intermediate axial-vector resonance is generated for certain values of the chiral couplings. We exemplify our analysis with a benchmark axial-vector with $M_A=3$ TeV. Interestingly enough, these different approaches provide essentially the same prediction. Finally we discuss the sensitivity of ATLAS and CMS to such resonances.

    hep-phJHEP(2018)·10 citations
15. 15*

    Hyperasymptotics and quark-hadron duality violations in QCD

    Diogo Boito🇧🇷 · Irinel Caprini🇷🇴 · Maarten Golterman🇺🇸 · Kim Maltman🇨🇦 · Santiago Peris🇪🇸

    We investigate the origin of the quark-hadron duality-violating terms in the expansion of the QCD two-point vector correlation function at large energies in the complex $q^2$ plane. Starting from the dispersive representation for the associated polarization, the analytic continuation of the operator product expansion from the Euclidean to the Minkowski region is performed by means of a generalized Borel-Laplace transform, borrowing techniques from hyperasymptotics. We establish a connection between singularities in the Borel plane and quark-hadron duality violating contributions. Starting with the assumption that for QCD at $N_c=\infty$ the spectrum approaches a Regge trajectory at large energy, we obtain an expression for quark-hadron duality violations at large, but finite $N_c$.

    hep-phhep-thnucl-thPRD(2018)·57 citations
16. 16*

    Testing a lepton quarticity flavor theory of neutrino oscillations with the DUNE experiment

    Rahul Srivastava🇪🇸 · C. A. Ternes🇪🇸 · M. Tórtola🇪🇸 · J. W. F. Valle🇪🇸

    Oscillation studies play a central role in elucidating at least some aspects of the flavor problem. Here we examine the status of the predictions of a lepton quarticity flavor theory of neutrino oscillations against the existing global sample of oscillation data. By performing quantitative simulations we also determine the potential of the upcoming DUNE experiment in narrowing down the currently ill-measured oscillation parameters ${\theta }_{23}$ and ${\delta }_{\text{CP}}$. We present the expected improved sensitivity on these parameters for different assumptions.

    hep-phhep-exPLB(2018)·34 citations
17. 17*

    Off-shell production of top-antitop pairs in the lepton+jets channel at NLO QCD

    Ansgar Denner🇩🇪 · Mathieu Pellen🇩🇪

    The production of top-quark pairs that subsequently decay hadronically and leptonically (lepton+jets channel) is one of the key processes for the study of top-quark properties at the LHC. In this article, NLO QCD corrections of order $\mathcal{O}\left({\alpha }_{\mathrm{s}}^3{\alpha }^4\right)$ to the hadronic process $\mathrm{p}\mathrm{p}\to {\mu }^{-}{\bar{\nu }}_{\mu }\mathrm{b}\bar{\mathrm{b}}\mathrm{j}\mathrm{j}$ are presented. The computation includes off-shell as well as non-resonant contributions, and experimental event selections are used in order to provide realistic predictions. The results are provided in the form of cross sections and differential distributions. The QCD corrections are sizeable and different from the ones of the fully leptonic channel. This is due to the different final state where here four jets are present at leading order.

    hep-phhep-exJHEP(2018)·56 citations
18. 18*

    Effective description of general extensions of the Standard Model: the complete tree-level dictionary

    J. de Blas🇮🇹 · J. C. Criado🇪🇸 · M. Perez-Victoria🇪🇸 · J. Santiago🇪🇸

    We compute all the tree-level contributions to the Wilson coefficients of the dimension-six Standard-Model effective theory in ultraviolet completions with general scalar, spinor and vector field content and arbitrary interactions. No assumption about the renormalizability of the high-energy theory is made. This provides a complete ultraviolet/infrared dictionary at the classical level, which can be used to study the low-energy implications of any model of interest, and also to look for explicit completions consistent with low-energy data.

    hep-phhep-thJHEP(2018)·342 citations
19. 19*

    Partially composite Higgs models: Phenomenology and RG analysis

    Tommi Alanne🇩🇪 · Diogo Buarque Franzosi🇩🇪 · Mads T. Frandsen🇩🇰 · Mette L.A. Kristensen🇩🇰 · Aurora Meroni🇫🇮 · Martin Rosenlyst🇩🇰

    We study the phenomenology of partially composite-Higgs models where electroweak symmetry breaking is dynamically induced, and the Higgs is a mixture of a composite and an elementary state. The models considered have explicit realizations in terms of gauge-Yukawa theories with new strongly interacting fermions coupled to elementary scalars and allow for a very SM-like Higgs state. We study constraints on their parameter spaces from vacuum stability and perturbativity as well as from LHC results and find that requiring vacuum stability up to the compositeness scale already imposes relevant constraints. A small part of parameter space around the classically conformal limit is stable up to the Planck scale. This is however already strongly disfavored by LHC results. In different limits, the models realize both (partially) composite-Higgs and (bosonic) technicolor models and a dynamical extension of the fundamental Goldstone-Higgs model. Therefore, they provide a general framework for exploring the phenomenology of composite dynamics.

    hep-phJHEP(2018)·25 citations
20. 20*

    Non-resonant and electroweak NNLO correction to the $e^{+}{e}^{-}$ top anti-top threshold

    Martin Beneke🇩🇪 · Andreas Maier🇬🇧 · Thomas Rauh🇬🇧 · Pedro Ruiz-Femenia🇪🇸

    We determine the NNLO electroweak correction to the $e^{+}{e}^{-}\to b\bar{b}{W}^{+}{W}^{-}X$ production cross section near the top-pair production threshold. The calculation includes non-resonant production of the final state as well as electroweak effects in resonant top anti-top pair production with non-relativistic resummation, and elevates the theoretical prediction to NNNLO QCD plus NNLO electroweak accuracy. We then study the impact of the new contributions on the top-pair threshold scan at a future lepton collider.

    hep-phJHEP(2018)·49 citations
21. 21*

    Neutrinoless Double Beta Decay and the Baryon Asymmetry of the Universe

    Frank F. Deppisch🇬🇧 · Lukas Graf🇬🇧 · Julia Harz🇫🇷 · Wei-Chih Huang🇩🇰

    We discuss the impact of the observation of neutrinoless double beta decay on the washout of lepton number in the early universe. Neutrinoless double beta decay can be triggered by a large number of mechanisms that can be encoded in terms of Standard Model effective operators which violate lepton number by two units. We calculate the contribution of such operators to the rate of neutrinoless double beta decay and correlate it with the washout of lepton number induced by the same operators in the early universe. We find that the observation of a non-standard contribution to neutrinoless double beta decay, i.e. not induced by the standard mass mechanism of light neutrino exchange, would correspond to an efficient washout of lepton number above the electroweak scale for many operators up to mass dimension 11. Combined with Standard Model sphaleron transitions, this would render many baryogenesis mechanisms at higher scales ineffective.

    hep-phPRD(2018)·89 citations
22. 22*

    QCD Axion Dark Matter with a Small Decay Constant

    Raymond T. Co🇺🇸 · Lawrence J. Hall🇺🇸 · Keisuke Harigaya🇺🇸

    The QCD axion is a good dark matter candidate. The observed dark matter abundance can arise from misalignment or defect mechanisms, which generically require an axion decay constant $f_a\sim \mathcal{O}(10^{11})$ GeV (or higher). We introduce a new cosmological origin for axion dark matter, parametric resonance from oscillations of the Peccei-Quinn symmetry breaking field, that requires $f_a\sim (10^8-10^{11})$ GeV. The axions may be warm enough to give deviations from cold dark matter in Large Scale Structure.

    hep-phastro-ph.COPRL(2018)·126 citations
23. 23*

    Tensor Modes in Pure Natural Inflation

    Yasunori Nomura🇺🇸 · Masahito Yamazaki🇯🇵

    We study tensor modes in pure natural inflation (arXiv:1706.08522), a recently-proposed inflationary model in which an axionic inflaton couples to pure Yang-Mills gauge fields. We find that the tensor-to-scalar ratio r is naturally bounded from below. This bound originates from the finiteness of the number of metastable branches of vacua in pure Yang-Mills theories. Details of the model can be probed by future cosmic microwave background experiments and improved lattice gauge theory calculations of the theta-angle dependence of the vacuum energy.

    hep-phastro-ph.COhep-lathep-thPLB(2018)·15 citations
24. 24*

    Flavoured Dark Matter Moving Left

    Monika Blanke🇩🇪 · Satrajit Das🇮🇳 · Simon Kast🇩🇪

    We investigate the phenomenology of a simplified model of flavoured Dark Matter (DM), with a dark fermionic flavour triplet coupling to the left-handed $SU(2{)}_L$ quark doublets via a scalar mediator. The DM-quark coupling matrix is assumed to constitute the only new source of flavour and CP violation, following the hypothesis of Dark Minimal Flavour Violation. We analyse the constraints from LHC searches, from meson mixing data in the $K$, $D$, and $B_{d,s}$ meson systems, from thermal DM freeze-out, and from direct detection experiments. Our combined analysis shows that while the experimental constraints are similar to the DMFV models with DM coupling to right-handed quarks, the multitude of couplings between DM and the SM quark sector resulting from the $SU(2{)}_L$ structure implies a richer phenomenology and significantly alters the resulting impact on the viable parameter space.

    hep-phhep-exJHEP(2018)·31 citations
25. 25*

    Dark neutrino interactions make gravitational waves blue

    Subhajit Ghosh🇮🇳 · Rishi Khatri🇮🇳 · Tuhin S. Roy🇮🇳

    New interactions of neutrinos can stop them from free streaming in the early Universe even after the weak decoupling epoch. This results in the enhancement of the primordial gravitational wave amplitude on small scales compared to the standard $\Lambda$CDM prediction. In this paper we calculate the effect of dark matter neutrino interactions in CMB tensor $B$-modes spectrum. We show that the effect of new neutrino interactions generates a scale or $\ell$ dependent imprint in the CMB $B$-modes power spectrum at $\ell \gtrsim 100$. In the event that primordial $B$-modes are detected by future experiments, a departure from scale invariance, with a blue spectrum, may not necessarily mean failure of simple inflationary models but instead may be a sign of non-standard interactions of relativistic particles. New interactions of neutrinos also induce a phase shift in the CMB B-mode power spectrum which cannot be mimicked by simple modifications of the primordial tensor power spectrum. There is rich information hidden in the CMB $B$-modes spectrum beyond just the tensor to scalar ratio.

    ↳ astro-ph.COhep-phPRD(2018)·24 citations
26. 26*

    Electromagnetic Duality and the Electric Memory Effect

    Yuta Hamada🇯🇵 · Min-Seok Seo🇰🇷 · Gary Shiu🇺🇸

    We study large gauge transformations for soft photons in quantum electrodynamics which, together with the helicity operator, form an ISO(2) algebra. We show that the two non-compact generators of the ISO(2) algebra correspond respectively to the residual gauge symmetry and its electromagnetic dual gauge symmetry that emerge at null infinity. The former is helicity universal (electric in nature) while the latter is helicity distinguishing (magnetic in nature). Thus, the conventional large gauge transformation is electric in nature, and is naturally associated with a scalar potential. We suggest that the electric Aharonov-Bohm effect is a direct measure for the electromagnetic memory arising from large gauge transformations.

    ↳ hep-thgr-qchep-phJHEP(2018)·22 citations
27. 27*

    New methods for B meson decay constants and form factors from lattice NRQCD

    C. Hughes🇺🇸 · C. T. H. Davies🇬🇧 · C. J. Monahan🇺🇸

    We determine the normalisation of scalar and pseudoscalar current operators made from non-relativistic $b$ quarks and Highly Improved Staggered light quarks in lattice Quantum Chromodynamics (QCD) through $\mathcal{O}({\alpha }_s)$ and ${\Lambda }_{\text{QCD}}/m_b$. We use matrix elements of these operators to extract $B$ meson decay constants and form factors, then compare to those obtained using the standard vector and axial-vector operators. This provides a test of systematic errors in the lattice QCD determination of the $B$ meson decay constants and form factors. We provide a new value for the $B$ and $B_s$ meson decay constants from lattice QCD calculations on ensembles that include $u$, $d$, $s$ and $c$ quarks in the sea and those which have the $u/d$ quark mass going down to its physical value. Our results are $f_B=0.196(6)$ GeV, $f_{B_s}=0.236(7)$ GeV and $f_{B_s}/f_B=1.207(7)$, agreeing well with earlier results using the temporal axial current. By combining with these previous results, we provide updated values of $f_B=0.190(4)$ GeV, $f_{B_s}=0.229(5)$ GeV and $f_{B_s}/f_B=1.206(5)$.

    ↳ hep-lathep-phPRD(2018)·93 citations
28. 28*

    Noether symmetry approach in the cosmological alpha-attractors

    Narakorn Kaewkhao (Prince Songkla U.)🇹🇭 · Thanyagamon Kanesom (Prince Songkla U.)🇹🇭 · Phongpichit Channuie (Walailak U.)🇹🇭

    In cosmological framework, Noether symmetry technique has revealed a useful tool in order to examine exact solutions. In this work, we first introduce the Jordan-frame Lagrangian and apply the conformal transformation in order to obtain the Lagrangian equivalent to Einstein-frame form. We then analyse the dynamics of the field in the cosmological alpha-attractors using the Noether sysmetry approach by focusing on the single field scenario in the Einstein-frame form. We show that with a Noether symmetry the coresponding dynamical system can be completely integrated and the potential exhibited by the symmetry can be exactly obtained. With the proper choice of parameters, the behavior of the scale factor displays an exponential (de Sitter) behavior at the present epoch. Moreover, we discover that the Hubble parameters strongly depends on the initial values of parameters exhibited by the Noether symmetry. Interestingly, it can retardedly evolve and becomes a constant in the present epoch in all cases.

    ↳ gr-qchep-phhep-thNPB(2018)·9 citations
29. 29*

    Measurement of anisotropy of dark matter velocity distribution using directional detection

    Keiko I. Nagao🇯🇵

    Although the velocity distribution of dark matter is assumed to be generally isotropic, some studies have found that $\sim 25$\% of the distribution can have anisotropic components. As the directional detection of dark matter is sensitive to both the recoil energy and direction of nuclear recoil, directional information can prove useful in measuring the distribution of dark matter. Using a Monte Carlo simulation based on the modeled directional detection of dark matter, we analyze the differences between isotropic and anisotropic distributions and show that the isotropic case can be rejected at a 90\% confidence level if $O(10^4)$ events can be obtained.

    ↳ astro-ph.COhep-exhep-phEPJ Web Conf.(2018)·0 citations
30. 30*

    Gauge copies in the Landau-DeWitt gauge: a background invariant restriction

    D. Dudal🇧🇪 · D. Vercauteren🇻🇳

    The Landau background gauge, also known as the Landau-DeWitt gauge, has found renewed interest during the past decade given its usefulness in accessing the confinement-deconfinement transition via the vacuum expectation value of the Polyakov loop, describable via an appropriate background. In this Letter, we revisit this gauge from the viewpoint of it displaying gauge (Gribov) copies. We generalize the Gribov-Zwanziger effective action in a BRST and background invariant way; this action leads to a restriction on the allowed gauge fluctuations, thereby eliminating the infinitesimal background gauge copies. The explicit background invariance of our action is in contrast with earlier attempts to write down and use an effective Gribov-Zwanziger action. It allows to address certain subtleties arising in these earlier works, such as a spontaneous and thus spurious Lorentz symmetry breaking, something which is now averted.

    ↳ hep-thhep-lathep-phPLB(2018)·16 citations
31. 31*

    Transport coefficients in a finite volume Polyakov--Nambu--Jona-Lasinio model

    Kinkar Saha🇮🇳 · Sabyasachi Ghosh🇮🇳 · Sudipa Upadhaya🇮🇳 · Soumitra Maity🇮🇳

    Finite size consideration of matter significantly affects transport coefficients like shear viscosity, bulk viscosity, electrical conductivity, which we have investigated here in the framework of the Polyakov-Nambu-Jona-Lasinio model. Owing to the basic quantum mechanics, a non-zero lower momentum cut-off is implemented in momentum integrations, used in the expressions of constituent quark masses and transport coefficients. When the system size decreases, the values of these trans- port coefficients are enhanced in low temperature range. At high temperature domain, shear viscos- ity and electrical conductivity become independent of system sizes. Whereas, bulk viscosity, which is associated with scale violating quantities of the system, faces some non-trivial size dependence in this regime. In the phenomenological direction, our microscopic estimations can also be linked with the macroscopic outcome, based on dissipative hydrodynamical simulation.

    ↳ nucl-thhep-phPRD(2018)·33 citations
32. 32*

    Radiative Kähler moduli stabilization

    Tatsuo Kobayashi🇯🇵 · Naoya Omoto🇯🇵 · Hajime Otsuka🇯🇵 · Takuya H. Tatsuishi🇯🇵

    We propose a new type of Kähler moduli stabilization mechanisms in type IIB superstring theory on Calabi-Yau manifolds with the positive Euler number. The overall Kähler modulus can be perturbatively stabilized by radiative corrections due to sparticles. Its minimum is the anti-de Sitter vacuum, where supersymmetry is broken. We can uplift it to the de Sitter vacuum by introducing anti-D-branes, keeping the modulus stabilized. Although our numerical results depend on the choice of the cutoff scale and degeneracies of sparticles, at any rate there exist the parameter spaces where the masses of Kaluza-Klein and stringy modes are larger than the cutoff scale. Furthermore, this stabilization scenario predicts an ultralight axion.

    ↳ hep-thhep-phPRD(2018)·9 citations
33. 33*

    Dilepton production and resonance properties within a new hadronic transport approach in the context of the GSI-HADES experimental data

    Jan Staudenmaier🇩🇪 · Janus Weil🇩🇪 · Vinzent Steinberg🇩🇪 · Stephan Endres🇩🇪 · Hannah Petersen🇩🇪

    The dilepton emission in heavy-ion reactions at low beam energies is examined within a hadronic transport approach. In this article the production of electron-positron pairs from a new approach named SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced. The dilepton emission is consistently taken into account below the hadronic threshold. The calculations are systematically confronted with HADES data in the kinetic energy range of $1-3.5A$ GeV for elementary, proton-nucleus and nucleus-nucleus reactions. The present approach employing a resonance treatment based on vacuum properties is validated by an excellent agreement with experimental data up to system sizes of carbon-carbon collisions. After establishing this well-understood baseline in elementary and small systems, the significance of medium effects is investigated with a coarse-graining approach based on the same hadronic evolution. The effect of explicit in-medium modifications to the vector meson spectral functions is important for dilepton invariant mass spectra in ArKCl and larger systems, even though the transport approach with vacuum properties reveals similar features due the coupling to baryonic resonance and the intrinsically included collisional broadening. This article provides a comprehensive comparison of our calculations with published dielectron results from the HADES collaboration. In addition, the emission of dileptons is predicted in gold-gold and pion-beam experiments for which results are expected soon.

    ↳ nucl-thhep-phnucl-exPRC(2018)·62 citations
34. 34*

    Higher cumulants of baryon number in critical QCD

    Nikolaos G. Antoniou🇬🇷 · Fotios K. Diakonos🇬🇷 · Nikolaos Kalntis🇬🇷 · Alexandros Kanargias🇬🇷

    We study the higher moments of the baryon number in the immediate neighbourhood of the QCD critical endpoint within the framework of Ising-QCD thermodynamics (N.~G. Antoniou {\it et al}, arXiv:1705.09124 [hep-ph]). We show that the kurtosis, as a function of the freeze-out baryon chemical potential, attains a sharp minimum very close to the critical point. We argue that the sharpness of this minimum is due to the narrowness of the critical region in the chemical potential direction. Our analysis reveals that the broad minimum of the kurtosis observed in Au+Au central collisions at STAR (in RHIC-BES I) in the colliding energy region $17$ GeV $<\sqrt{s}<$ $39$ GeV is apparently only a precursor of the critical point and not a signature of its location.

    ↳ nucl-thhep-phNPA(2019)·4 citations
35. 35*

    Massive gravity and the suppression of anisotropies and gravitational waves in a matter-dominated contracting universe

    Chunshan Lin🇵🇱 · Jerome Quintin🇨🇦 · Robert H. Brandenberger🇨🇦

    We consider a modified gravity model with a massive graviton, but which nevertheless only propagates two gravitational degrees of freedom and which is free of ghosts. We show that non-singular bouncing cosmological background solutions can be generated. In addition, the mass term for the graviton prevents anisotropies from blowing up in the contracting phase and also suppresses the spectrum of gravitational waves compared to that of the scalar cosmological perturbations. This addresses two of the main problems of the matter bounce scenario.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2018)·22 citations
36. 36*

    Cosmic Acceleration in the Nonlocal Approach to the Cosmological Constant Problem

    Ichiro Oda🇯🇵

    We have recently constructed a manifestly local formulation of a nonlocal approach to the cosmological constant problem which can treat with quantum effects from both matter and gravitational fields. In this formulation, it has been explicitly shown that the effective cosmological constant is radiatively stable even in the presence of the gravitational loop effects. Since we are naturally led to add the $R^2$ term and the corresponding topological action to an original action, we make use of this formulation to account for the late-time acceleration of expansion of the universe in case of the open universes with infinite space-time volume. We will see that when the "scalaron", which exists in the $R^2$ gravity as an extra scalar field, has a tiny mass of the order of magnitude $\mathcal{O}(1meV)$, we can explain the current value of the cosmological constant in a consistent manner.

    ↳ hep-thgr-qchep-phEPJC(2018)·4 citations
37. 37*

    Anomaly matching for phase diagram of massless ${\mathbb{Z}}_N$-QCD

    Yuya Tanizaki🇺🇸 · Yuta Kikuchi🇯🇵 · Tatsuhiro Misumi🇯🇵 · Norisuke Sakai🇯🇵

    We elucidate that the phase diagram of massless $N$-flavor QCD under ${\mathbb{Z}}_N$ flavor-twisted boundary condition (massless ${\mathbb{Z}}_N$-QCD) is constrained by an 't Hooft anomaly involving two-form gauge fields. As a consequence, massless ${\mathbb{Z}}_N$-QCD turns out to realize persistent order at any temperatures and quark chemical potentials, namely, the symmetric and gapped phase is strictly forbidden. This is the first result on the finite-$(T,\mu )$ phase diagram in QCD-type theories based on anomaly matching related to center and discrete axial symmetries.

    ↳ hep-thcond-mat.str-elhep-lathep-ph+1PRD(2018)·98 citations
38. 38*

    Revealing the Dark Matter Halo with Axion Direct Detection

    Joshua W. Foster🇺🇸 · Nicholas L. Rodd🇺🇸 · Benjamin R. Safdi🇺🇸

    The next generation of axion direct detection experiments may rule out or confirm axions as the dominant source of dark matter. We develop a general likelihood-based framework for studying the time-series data at such experiments, with a focus on the role of dark-matter astrophysics, to search for signatures of the QCD axion or axion like particles. We illustrate how in the event of a detection the likelihood framework may be used to extract measures of the local dark matter phase-space distribution, accounting for effects such as annual modulation and gravitational focusing, which is the perturbation to the dark matter phase-space distribution by the gravitational field of the Sun. Moreover, we show how potential dark matter substructure, such as cold dark matter streams or a thick dark disk, could impact the signal. For example, we find that when the bulk dark matter halo is detected at 5$\sigma$ global significance, the unique time-dependent features imprinted by the dark matter component of the Sagittarius stream, even if only a few percent of the local dark matter density, may be detectable at $\sim$2$\sigma$ significance. A co-rotating dark disk, with lag speed $\sim$50 km$/$s, that is $\sim$20$\%$ of the local DM density could dominate the signal, while colder but as-of-yet unknown substructure may be even more important. Our likelihood formalism, and the results derived with it, are generally applicable to any time-series based approach to axion direct detection.

    ↳ astro-ph.COhep-phPRD(2018)·269 citations
39. 39*

    Oscillons from Pure Natural Inflation

    Jeong-Pyong Hong🇯🇵 · Masahiro Kawasaki🇯🇵 · Masahito Yamazaki🇯🇵

    We examine the oscillon formation in a recently proposed inflation model of the pure natural inflation, where the inflaton is an axion that couples to a strongly-coupled pure Yang-Mills theory. The plateau of the inflaton potential, which is favored by recent observations, drives the fragmentation of the inflaton and can produce spatially localized oscillons. We find that the oscillons are formed for F<~ O(0.1) M_{Pl}, with F the effective decay constant of the model. We also comment on observational implications of the oscillons.

    ↳ astro-ph.COhep-phhep-thPRD(2018)·40 citations
40. 40*

    ETHOS -- an effective theory of structure formation: predictions for the high-redshift Universe -- abundance of galaxies and reionization

    Mark R. Lovell (1,2,3)🇮🇸 · Jesús Zavala (1)🇮🇸 · Mark Vogelsberger (4)🇺🇸 · Xuejian Shen (4) · Francis-Yan Cyr-Racine (5)🇺🇸 · Christoph Pfrommer (6)🇩🇪 · Kris Sigurdson (7)🇺🇸 · Michael Boylan-Kolchin (8)🇺🇸 · Annalisa Pillepich (3) ((1) University of Iceland, (2) Durham, (3) MPIA, (4) MIT, (5) Harvard, (6) AIP, (7) UBC, (8) UT Austin)🇩🇪

    We contrast predictions for the high-redshift galaxy population and reionization history between cold dark matter (CDM) and an alternative self-interacting dark matter model based on the recently developed ETHOS framework that alleviates the small-scale CDM challenges within the Local Group. We perform the highest resolution hydrodynamical cosmological simulations (a 36~Mpc${}^3$ volume with gas cell mass of $\sim 10^5{\mathrm{M}}_{\odot }$ and minimum gas softening of $\sim 180$~pc) within ETHOS to date -- plus a CDM counterpart -- to quantify the abundance of galaxies at high redshift and their impact on reionization. We find that ETHOS predicts galaxies with higher ultraviolet (UV) luminosities than their CDM counterparts and a faster build-up of the faint end of the UV luminosity function. These effects, however, make the optical depth to reionization less sensitive to the power spectrum cut-off: the ETHOS model differs from the CDM $\tau$ value by only 10 per cent and is consistent with Planck limits if the effective escape fraction of UV photons is 0.1-0.5. We conclude that current observations of high-redshift luminosity functions cannot differentiate between ETHOS and CDM models, but deep JWST surveys of strongly-lensed, inherently faint galaxies have the potential to test non-CDM models that offer attractive solutions to CDM's Local Group problems.

    ↳ astro-ph.COhep-phMNRAS(2018)·57 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.