Thu·Jun 15, 2017Thursday·June 15, 2017

1. 01*

   Jet-associated resonance spectroscopy

   Christoph Englert🇬🇧 · Gabriele Ferretti🇸🇪 · Michael Spannowsky🇬🇧

   We present a model-independent study aimed at characterizing the nature of possible resonances in the jet-photon or jet-$Z$ final state at hadron colliders. Such resonances are expected in many models of compositeness and would be a clear indication of new physics. At leading order, in the narrow width approximation, the matrix elements are parameterized by just a few constants describing the coupling of the various helicities to the resonance. We present the full structure of such amplitudes up to spin two and use them to simulate relevant kinematic distributions that could serve to constrain the coupling structure. This also generalizes the signal generation strategy that is currently pursued by ATLAS and CMS to the most general case in the considered channels. While the determination of the P/CP properties of the interaction seems to be out of reach within this framework, there is a wealth of information to be gained about the spin of the resonance and the relative couplings of the helicities.

   hep-phhep-exEPJC(2017)·5 citations
2. 02*

   Predictions from a flavour GUT model combined with a SUSY breaking sector

   Stefan Antusch🇨🇭 · Christian Hohl🇨🇭

   We discuss how flavour GUT models in the context of supergravity can be completed with a simple SUSY breaking sector, such that the flavour-dependent (non-universal) soft breaking terms can be calculated. As an example, we discuss a model based on an SU(5) GUT symmetry and $A_4$ family symmetry, plus additional discrete "shaping symmetries" and a ${\mathbb{Z}}_4^{\mathrm{R}}$ symmetry. We calculate the soft terms and identify the relevant high scale input parameters, and investigate the resulting predictions for the low scale observables, such as flavour violating processes, the sparticle spectrum and the dark matter relic density.

   hep-phJHEP(2017)·12 citations
3. 03*

   Impact of the $b\to sll$ anomalies on dark matter physics

   Junichiro Kawamura🇯🇵 · Shohei Okawa🇯🇵 · Yuji Omura🇯🇵

   Recently, the LHCb collaboration has reported the excesses in the $b\to sll$ processes. One of the promising candidates for new physics to explain the anomalies is the extended Standard Model (SM) with vector-like quarks and leptons. In that model, Yukawa couplings between the extra fermions and SM fermions are introduced, adding extra scalars. Then, the box diagrams involving the extra fields achieve the $b\to sll$ anomalies. It has been known that the excesses require the large Yukawa couplings of leptons, so that this kind of model can be tested by studying correlations with other observables. In this paper, we consider the extra scalar to be a dark matter (DM) candidate, and investigate DM physics as well as the flavor physics and the LHC physics. The DM relic density and the direct-detection cross section are also dominantly given by the Yukawa couplings, so that we find some explicit correlations between DM physics and the flavor physics. In particular, we find the predictions of the $b\to sll$ anomalies against the direct detection of DM.

   hep-phhep-exPRD(2017)·53 citations
4. 04*

   CSM analyses of $t\bar{t}H,t\bar{t}Z,t\bar{b}{W}^{-}$ production in gluon-gluon and photon-photon collisions

   Fernand M. Renard🇫🇷

   We extend our previous analysis of $t\bar{t}H,t\bar{t}Z,t\bar{b}W$ production in $e^{+}{e}^{-}$ collisions within the CSM (Composite Standard Model) concept of Higgs boson and top quark compositeness to the case of gluon-gluon and photon-photon collisions. We show that remarkable differences may indeed appear between the effects generated by CSM conserving and by CSM violating sets of form factors.

   hep-ph1 citation
5. 05*

   Spectral Decomposition of Missing Transverse Energy at Hadron Colliders

   Kyu Jung Bae🇰🇷 · Tae Hyun Jung🇰🇷 · Myeonghun Park🇰🇷

   We propose a spectral decomposition to systematically extract information of dark matter at hadron colliders. The differential cross section of events with missing transverse energy (MET) can be expressed by a linear combination of basis functions. In the case of $s$-channel mediator models for dark matter particle production, basis functions are identified with the differential cross sections of sub-processes of virtual mediator and visible particle production while the coefficients of basis functions correspond to dark matter invariant mass distribution in the manner of the Källén-Lehmann spectral decomposition. For a given MET data set and mediator model, we show that one can differentiate a certain dark matter-mediator interaction from another through spectral decomposition.

   hep-phPRL(2017)·6 citations
6. 06*

   Anomalous low-temperature thermodynamics of QCD in strong magnetic fields

   Tomas Brauner🇳🇴 · Saurabh Kadam🇮🇳

   The thermodynamics of quantum chromodynamics at low temperatures and in sufficiently strong magnetic fields is governed by neutral pions. We analyze the interacting system of neutral pions and photons at zero baryon chemical potential using effective field theory. As a consequence of the axial anomaly and the external magnetic field, the pions and photons mix with one another. The resulting spectrum contains one usual, relativistic photon state, and two nonrelativistic modes, one of which is gapless and the other gapped. Furthermore, we calculate the leading, one-loop contribution to the pressure of the system. In the chiral limit, a closed analytic expression for the pressure exists, which features an unusual scaling with temperature and magnetic field, $T^{3}B/f_{\pi }$, at low temperatures, $T\ll B/f_{\pi }$. Finally, we determine the pion decay rate as a function of the magnetic field at the tree level. The result is affected by a competition of the anisotropic kinematics and the enlarged phase space due to the anomalous mass of the neutral pion. In the chiral limit, the decay rate scales as $B^3/f_{\pi }^5$.

   hep-phhep-thJHEP(2017)·28 citations
7. 07*

   Dynamical Clockwork Axions

   Rupert Coy🇫🇷 · Michele Frigerio🇫🇷 · Masahiro Ibe🇯🇵

   The clockwork mechanism is a novel method for generating a large separation between the dynamical scale and interaction scale of a theory. We demonstrate how the mechanism can arise from a sequence of strongly-coupled sectors. This framework avoids elementary scalar fields as well as ad hoc continuous global symmetries, both of which are subject to serious stability issues. The clockwork factor, $q$, is determined by the consistency of the strong dynamics. The preserved global $U(1)$ of the clockwork appears as an accidental symmetry, resulting from discrete or $U(1)$ gauge symmetries, and it is spontaneously broken by the chiral condensates. We apply such a dynamical clockwork to construct models with an effectively invisible QCD axion from TeV-scale strong dynamics. The axion couplings are determined by the localisation of the Standard Model interactions along the clockwork sequence. The TeV spectrum includes either coloured hadrons or vector-like quarks. Dark matter can be accounted for by the axion or the lightest neutral baryons, which are accidentally stable.

   hep-phJHEP(2017)·47 citations
8. 08*

   Least Fine-Tuned U(1) Extended SSM

   Yasar Hicyilmaz🇹🇷 · Levent Solmaz🇹🇷 · Sukru Hanif Tanyildizi🇹🇷 · Cem Salih Un🇹🇷

   We consider the Higgs boson mass in a class of the UMSSM models in which the MSSM gauge group is extended by an additional U(1)' group. Implementing the universal boundary conditions at the GUT scale we target phenomenologically interesting regions of UMSSM where the necessary radiative contributions to the lightest CP-even Higgs boson mass are significantly small and LSP is always the lightest neutralino. We find that the smallest amount of radiative contributions is about 50 GeV in UMSSM, this result is much lower than that obtained in MSSM, which is around 90 GeV. Additionally, we examine the Higgs boson properties in these models to check if it can behave similar to the SM Higgs boson under the current experimental constraints. We find that enforcement of smaller radiative contribution mostly restricts the U(1)' breaking scale as v_S <~ 10 TeV. Besides, such low contributions demand h_S ~ 0.2 - 0.45. Because of the model dependency in realizing these radiative contributions theta_E_6 < 0 are more favored, if one seeks for the solutions consistent with the current dark matter constraints. As to the mass spectrum, we find that stop and stau can be degenerate with the LSP neutralino in the range from 300 GeV to 700 GeV; however, the dark matter constraints restrict this scale as m_stop, m_stau >~ 500$ GeV. Such degenerate solutions also predict stop-neutralino and stau-neutralino coannihilation channels, which are effective to reduce the relic abundance of neutralino down to the ranges consistent with the current dark matter observations. Finally, we discuss the effects of heavy M_Z' in the fine-tuning. Even though the radiative contributions are significantly low, the required fine-tuning can still be large. We comment about reinterpretation of the fine-tuning measure in the UMSSM framework, which can yield efficiently low results for the fine-tuning at the electroweak scale.

   hep-phNPB(2018)·9 citations
9. 09*

   Toward a unified interpretation of quark and lepton mixing from flavor and CP symmetries

   Cai-Chang Li🇨🇳 · Jun-Nan Lu🇨🇳 · Gui-Jun Ding🇨🇳

   We discussed the scenario that a discrete flavor group combined with CP symmetry is broken to $Z_2\times CP$ in both neutrino and charged lepton sectors. All lepton mixing angles and CP violation phases are predicted to depend on two free parameters ${\theta }_l$ and ${\theta }_{\nu }$ varying in the range of $[0,\pi )$. As an example, we comprehensively study the lepton mixing patterns which can be derived from the flavor group $\Delta (6n^2)$ and CP symmetry. Three kinds of phenomenologically viable lepton mixing matrices are obtained up to row and column permutations. We further extend this approach to the quark sector. The precisely measured quark mixing angles and CP invariant can be accommodated for certain values of the free parameters ${\theta }_u$ and ${\theta }_d$. A simultaneous description of quark and lepton flavor mixing structures can be achieved from a common flavor group $\Delta (6n^2)$ and CP, and accordingly the smallest value of the group index $n$ is $n=7$.

   hep-phJHEP(2018)·31 citations
10. 10*

    Discrepancies in simultaneous explanation of Flavor Anomalies and IceCube PeV Events using Leptoquarks

    Bhavesh Chauhan🇮🇳 · Bharti Kindra🇮🇳 · Ashish Narang🇮🇳

    Leptoquarks have been suggested to solve a variety of discrepancies between the expected and observed phenomenon. In this paper, we show that the scalar doublet Leptoquark with Hypercharge 7/6 can simultaneously explain the recent measurement of $R_K$, $R_{K^{\ast }}$, the excess in anomalous magnetic moment of muon, and the observed excess in IceCube HESE data. For appropriate choice of couplings, the flavor anomalies are generated at one-loop level and IceCube data is explained via resonant production of the Leptoquark. Several constraints from LHC searches are imposed on the model parameter space.

    hep-phPRD(2018)·46 citations
11. 11*

    On primordial black holes from an inflection point

    Cristiano Germani🇪🇸 · Tomislav Prokopec🇳🇱

    Recently, it has been claimed that inflationary models with an inflection point in the scalar potential can produce a large resonance in the power spectrum of curvature perturbation. In this paper however we show that the previous analyses are incorrect. The reason is twofold: firstly, the inflaton is over-shot from a stage of standard inflation and so deviates from the slow-roll attractor before reaching the inflection. Secondly, on the (or close to) the inflection point, the ultra-slow-roll trajectory supersede the slow-roll one and thus, the slow-roll approximations used in the literature cannot be used. We then reconsider the model and provide a recipe for how to produce nevertheless a large peak in the matter power spectrum via fine-tuning of parameters.

    ↳ astro-ph.COgr-qchep-phhep-thPhys.Dark Univ.(2017)·431 citations
12. 12*

    Small-$x$ Asymptotics of the Gluon Helicity Distribution

    Yuri V. Kovchegov🇺🇸 · Daniel Pitonyak🇺🇸 · Matthew D. Sievert🇺🇸

    We determine the small-$x$ asymptotics of the gluon helicity distribution in a proton at leading order in perturbative QCD at large $N_c$. To achieve this, we begin by evaluating the dipole gluon helicity TMD at small $x$. In the process we obtain an interesting new result: in contrast to the unpolarized dipole gluon TMD case, the operator governing the small-$x$ behavior of the dipole gluon helicity TMD is different from the operator corresponding to the polarized dipole scattering amplitude (used in our previous work to determine the small-$x$ asymptotics of the quark helicity distribution). We then construct and solve novel small-$x$ large-$N_c$ evolution equations for the operator related to the dipole gluon helicity TMD. Our main result is the small-$x$ asymptotics for the gluon helicity distribution: $\Delta G\sim {\left(\frac{1}{x}\right)}^{{\alpha }_h^G}$ with ${\alpha }_h^G=\frac{13}{4\sqrt{3}}\sqrt{\frac{{\alpha }_s{N}_c}{2\pi }}\approx 1.88\sqrt{\frac{{\alpha }_s{N}_c}{2\pi }}$. We note that the power ${\alpha }_h^G$ is approximately 20$\%$ lower than the corresponding power ${\alpha }_h^q$ for the small-$x$ asymptotics of the quark helicity distribution defined by $\Delta q\sim {\left(\frac{1}{x}\right)}^{{\alpha }_h^q}$ with ${\alpha }_h^q=\frac{4}{\sqrt{3}}\sqrt{\frac{{\alpha }_s{N}_c}{2\pi }}\approx 2.31\sqrt{\frac{{\alpha }_s{N}_c}{2\pi }}$ found in our earlier work.

    ↳ nucl-thhep-exhep-phnucl-exJHEP(2017)·115 citations
13. 13*

    Dark Matter Annihilation in the Circumgalactic Medium at High Redshifts

    Sarah Schon🇦🇺 · Katherine J. Mack🇦🇺 · Stuart B. Wyithe🇦🇺

    Annihilating dark matter (DM) models offer promising avenues for future DM detection, in particular via modification of astrophysical signals. However when modelling such potential signals at high redshift the emergence of both dark matter and baryonic structure, as well as the complexities of the energy transfer process, need to be taken into account. In the following paper we present a detailed energy deposition code and use this to examine the energy transfer efficiency of annihilating dark matter at high redshift, including the effects on baryonic structure. We employ the PYTHIA code to model neutralino-like DM candidates and their subsequent annihilation products for a range of masses and annihilation channels. We also compare different density profiles and mass-concentration relations for 10^5-10^7 M_sun haloes at redshifts 20 and 40. For these DM halo and particle models, we show radially dependent ionisation and heating curves and compare the deposited energy to the haloes' gravitational binding energy. We use the "filtered" annihilation spectra escaping the halo to calculate the heating of the circumgalactic medium and show that the mass of the minimal star forming object is increased by a factor of 2-3 at redshift 20 and 4-5 at redshift 40 for some DM models.

    ↳ astro-ph.COhep-phMNRAS(2018)·15 citations
14. 14*

    AdS/QCD, Entanglement Entropy and Critical Temperature

    M Lezgi🇮🇷 · M. Ali-Akbari🇮🇷

    Based on gauge-gravity duality, by using holographic entanglement entropy, we have done a phenomenological study to probe confinement-deconfinement phase transition in the QCD-like gauge theory. Our outcomes are in perfect agreement with the expected results, qualitatively and quantitatively. We find out that the (holographic) entanglement entropy is a reliable order parameter for probing the phase transition.

    ↳ hep-thhep-phPRD(2017)·24 citations
15. 15*

    Observing the very low-surface brightness dwarfs in a deep field in the VIRGO cluster: constraints on Dark Matter scenarios

    N. Menci🇮🇹 · E. Giallongo🇮🇹 · A. Grazian🇮🇹 · D. Paris🇮🇹 · A. Fontana🇮🇹 · L. Pentericci (INAF-Osservatorio Astronomico di Roma)🇮🇹

    We report the discovery of 11 very faint (r< 23), low surface brightness ({\mu}_r< 27 mag/arcsec^2) dwarf galaxies in one deep field in the Virgo cluster, obtained by the prime focus cameras (LBC) at the Large Binocular Telescope (LBT). These extend our previous sample to reach a total number of 27 galaxies in a field of just of 0.17 deg^2 located at a median distance of 390 kpc from the cluster center. Their association with the Virgo cluster is supported by their separate position in the central surface brightness - total magnitude plane with respect to the background galaxies of similar total magnitude. For a significant fraction (26\%) of the sample the association to the cluster is confirmed by spectroscopic follow-up. We show that the mere abundance of satellite galaxies corresponding to our observed number in the target field provides extremely tight constraints on Dark Matter models with suppressed power spectrum compared to the Cold Dark Matter case, independently of the galaxy luminosity distribution. In particular, requiring the observed number of satellite galaxies not to exceed the predicted abundance of Dark Matter sub-halos yields a limit m_X >3 keV at 1-{\sigma} and m_X > 2.3 keV at 2-{\sigma} confidence level for the mass of thermal Warm Dark Matter particles. Such a limit is competitive with other limits set by the abundance of ultra-faint satellite galaxies in the Milky Way, is completely independent of baryon physics involved in galaxy formation, and has the potentiality for appreciable improvements with next observations. We extend our analysis to Dark Matter models based on sterile neutrinos, showing that our observations set tight constraints on the combination of sterile neutrino mass m_{\nu} and mixing parameter sin^2(2{\theta}). We discuss the robustness of our results with respect to systematics.

    ↳ astro-ph.COastro-ph.GAhep-phAstron.Astrophys.(2017)·4 citations
16. 16*

    Fermion bound states in geometrically deformed backgrounds

    D. Bazeia🇧🇷 · A. Mohammadi🇧🇷 · D.C. Moreira🇧🇷

    This work deals with the behavior of fermions in the background of kinklike structures in the two-dimensional spacetime. The kinklike structures appear from bosonic scalar field models that engender distinct profiles and interact with the fermion fields via the standard Yukawa coupling. We first consider two models that engender parity symmetry, one leading to the exclusion of fermion bound states, and the other to the inclusion of bound states, when the parameter that controls the bosonic structure varies from zero to unity. We then go on and investigate another model where the kinklike solution explicitly breaks parity symmetry, leading to fermion bound states that are spatially asymmetric.

    ↳ hep-thcond-mat.mes-hallhep-phCPC(2019)·16 citations
17. 17*

    Note on lattice regularization and equal-time correlators for parton distribution functions

    G.C. Rossi🇮🇹 · M. Testa🇮🇹

    We show that a recent interesting idea to circumvent the difficulties with the continuation of parton distribution functions to the Euclidean region, that consists in looking at equal time correlators between proton states of infinite momentum, encounters some problems related to the power divergent mixing pattern of DIS operators, when implemented within the lattice regularization.

    ↳ hep-lathep-phPRD(2017)·63 citations
18. 18*

    False Vacuum Decay Catalyzed by Black Holes

    Kyohei Mukaida🇯🇵 · Masaki Yamada🇺🇸

    False vacuum states are metastable in quantum field theories, and true vacuum bubbles can be nucleated due to the quantum tunneling effect. It was recently suggested that an evaporating black hole (BH) can be a catalyst of bubble nucleations and dramatically shortens the lifetime of the false vacuum. In particular, in the context of the Standard Model valid up to a certain energy scale, even a single evaporating BH may spoil the successful cosmology by inducing the decay of our electroweak vacuum. In this paper, we reinterpret catalyzed vacuum decay by BHs, using an effective action for a thin-wall bubble around a BH to clarify the meaning of bounce solutions. We calculate bounce solutions in the limit of a flat spacetime and in the limit of negligible backreaction to the metric, where it is much easier to understand the physical meaning, and compare these results with the full calculations done in the literature. As a result, we give a physical interpretation of the enhancement factor: it is nothing but the probability of producing states with a finite energy. This makes it clear that all the other states such as plasma should also be generated through the same mechanism, and calls for finite-density corrections to the tunneling rate which tend to stabilize the false vacuum. We also clarify that the dominant process is always consistent with the periodicity indicated by the BH Hawking temperature after summing over all possible remnant BH masses or bubble energies, although the periodicity of each bounce solution as a function of a remnant BH can be completely different from the inverse temperature of the system as mentioned in the previous literature.

    ↳ hep-thgr-qchep-phPRD(2017)·81 citations
19. 19*

    Two-loop free energy of three-dimensional antiferromagnets in external magnetic and staggered fields

    Tomas Brauner🇳🇴 · Christoph P. Hofmann🇲🇽

    Using a model-independent low-energy effective field theory, we calculate the free energy of three-dimensional antiferromagnets in a combination of mutually perpendicular external magnetic and staggered fields at the next-to-next-to-leading, two-loop order. Renormalization is carried out analytically, and the renormalization group invariance of the result is checked explicitly. The free energy is thus expressed solely in terms of temperature, the external fields, and a set of low-energy coupling constants, to be determined by experiment or by matching to the microscopic model of a given concrete material.

    ↳ cond-mat.str-elhep-phhep-thAnnals Phys.(2017)·5 citations
20. 20*

    Short-distance matrix elements for $D^0$-meson mixing for $N_f=2+1$ lattice QCD

    A. Bazavov🇺🇸 · C. Bernard🇺🇸 · C. M. Bouchard🇬🇧 · C. C. Chang🇺🇸 · C. DeTar🇺🇸 · D. Du🇺🇸 · A. X. El-Khadra🇺🇸 · E. D. Freeland🇺🇸 · E. Gámiz🇪🇸 · Steven Gottlieb🇺🇸 · U. M. Heller🇺🇸 · A. S. Kronfeld🇺🇸 and 8 other authors

    We calculate in three-flavor lattice QCD the short-distance hadronic matrix elements of all five $\Delta C=2$ four-fermion operators that contribute to neutral $D$-meson mixing both in and beyond the Standard Model. We use the MILC Collaboration's $N_f=2+1$ lattice gauge-field configurations generated with asqtad-improved staggered sea quarks. We also employ the asqtad action for the valence light quarks and use the clover action with the Fermilab interpretation for the charm quark. We analyze a large set of ensembles with pions as light as $M_{\pi }\approx 180$ MeV and lattice spacings as fine as $a\approx 0.045$ fm, thereby enabling good control over the extrapolation to the physical pion mass and continuum limit. We obtain for the matrix elements in the $\overline{\text{MS}}$-NDR scheme using the choice of evanescent operators proposed by Beneke \emph{et al.}, evaluated at 3 GeV, $⟨D^0|{\mathcal{O}}_i|{\bar{D}}^0⟩=\{0.0805(55)(16),-0.1561(70)(31),0.0464(31)(9),0.2747(129)(55),0.1035(71)(21)\}{\text{GeV}}^4$ ($i=1$--5). The errors shown are from statistics and lattice systematics, and the omission of charmed sea quarks, respectively. To illustrate the utility of our matrix-element results, we place bounds on the scale of CP-violating new physics in $D^0$~mixing, finding lower limits of about 10--50$\times 10^3$ TeV for couplings of $\mathrm{O}(1)$. To enable our results to be employed in more sophisticated or model-specific phenomenological studies, we provide the correlations among our matrix-element results. For convenience, we also present numerical results in the other commonly-used scheme of Buras, Misiak, and Urban.

    ↳ hep-lathep-exhep-phPRD(2018)·66 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.