Thu·Feb 25, 2016Thursday·February 25, 2016

1. 01*

   Disformal scalars as dark matter candidates: Branon phenomenology

   Jose A. R. Cembranos🇪🇸 · Antonio L. Maroto🇪🇸

   Scalar particles coupled to the Standard Model fields through a disformal coupling arise in different theories, such as massive gravity or brane-world models. We will review the main phenomenology associated with such particles. Distinctive disformal signatures could be measured at colliders and with astrophysical observations. The phenomenological relevance of the disformal coupling demands the introduction of a set of symmetries, which may ensure the stability of these new degrees of freedom. In such a case, they constitute natural dark matter candidates since they are generally massive and weakly coupled. We will illustrate these ideas by paying particular attention to the branon case, since these questions arise naturally in brane-world models with low tension, where they were first discussed.

   hep-phastro-ph.COgr-qcInt.J.Mod.Phys.(2016)·18 citations
2. 02*

   Di-photon resonance and Dark Matter as heavy pions

   Michele Redi🇮🇹 · Alessandro Strumia🇨🇭 · Andrea Tesi🇺🇸 · Elena Vigiani🇮🇹

   We analyse confining gauge theories where the 750 GeV di-photon resonance is a composite techni-pion that undergoes anomalous decays into SM vectors. These scenarios naturally contain accidentally stable techni-pions Dark Matter candidates. The di-photon resonance can acquire a larger width by decaying into Dark Matter through the CP-violating $\theta$-term of the new gauge theory reproducing the cosmological Dark Matter density as thermal relic.

   hep-phJHEP(2016)·47 citations
3. 03*

   A see-saw scenario of an $A_4$ flavour symmetric standard model

   Dinh Nguyen Dinh🇻🇳 · Nguyen Anh Ky🇻🇳 · Phi Quang Văn🇻🇳 · Nguyen Thi Hông Vân🇻🇳

   A see-saw scenario for an $A_4$ flavour symmetric standard model is presented. The latter, compared with the standard model, has an extended field content adopting now an additional $A_4$ symmetry structure (along with the standard model symmetry). As before, the see-saw mechanism can be realized in several models of different types depending on different ways of neutrino mass generation corresponding to the introduction of new (heavy in general) fields with different symmetry structures. In the present paper, a general description of all these see-saw types is made with a more detailed investigation on type-I models, while for type-II and type-III models a similar strategy can be followed. As within the original see-saw mechanism, the symmetry structure of the standard model fields decides the number and the symmetry structure of the new fields. In a model considered here, the scalar sector consists of three standard-model-Higgs-like iso-doublets ($S{U}_L(2)$-doublets) forming together an $A_4$-triplet, and three iso-singlets transforming as three singlets (1,$1^{{}^{\prime }}$ and $1^{{}^{\prime \prime }}$) of $A_4$. In the lepton sector, the three left-handed lepton iso-doublets form an $A_4$-triplet, while the three right-handed charged leptons are either $A_4$-singlets in one version of the model, or components of an $A_4$-triplet in another version. To generate neutrino masses through, say, the type-I see-saw mechanism, it is natural to add four right-handed neutrino multiplets, including one $A_4$-triplet and three $A_4$-singlets. For an interpretation, the model is applied to deriving some physics quantities such as neutrinoless double beta decay effective mass $|⟨m_{ee}⟩|$, CP violation phase ${\delta }_{CP}$ and Jarlskog parameter $J_{CP}$, which can be verified experimentally.

   hep-ph14 citations
4. 04*

   Particle production with L-R neutrino oscillation

   Seishi Enomoto🇵🇱 · Tomohiro Matsuda🇯🇵

   When the Higgs field starts oscillation after Higgs inflation, gauge bosons are produced non-perturbatively near the Enhanced Symmetry Point (ESP). Just after the particle production, when the Higgs field is going away from the ESP, these gauge bosons gain mass and decay or annihilate into Standard Model (SM) fermions. Left-handed neutrinos can be generated in that way. If one assumes the see-saw mechanism, the mass matrix of a pair of left and right-handed neutrinos is non-diagonal. Although their mixing in the mass eigenstates is negligible in the true vacuum, it could be significant near the edge of the Higgs oscillation, where the off-diagonal component is large. Therefore, the left-handed neutrinos generated from the gauge bosons can start neutrino oscillation between the right-handed neutrinos. We study the particle production when such L-R neutrino oscillation is significant. For a working example, the non-thermal leptogenesis scenario after Higgs inflation is examined, which cannot be realized without the L-R neutrino oscillation. The same mechanism could be applied to other singlet particles whose abundance has been neglected.

   hep-phPRD(2016)·0 citations
5. 05*

   ${\eta }_c\to l^{+}{l}^{-}$ and ${\chi }_{c0}\to l^{+}{l}^{-}$ decays revisited

   N. Kivel🇩🇪 · A. Kupsc🇸🇪

   We present a calculation of ${\eta }_c\to l^{+}{l}^{-}$ and ${\chi }_{c0}\to l^{+}{l}^{-}$ decay widths. The amplitudes are computed within leading-order approximation using NRQCD framework. Numerical results for the branchings fractions are presented.

   hep-ph1 citation
6. 06*

   Bounds on LFV Higgs decays in a vector-like lepton model and searching for doubly charged leptons at the LHC

   Chuan-Hung Chen🇹🇼 · Takaaki Nomura🇰🇷

   The Higgs-portal lepton flavor violation is studied in a vectorlike lepton model. For evading the constraints from rare $Z\to {\ell }_i^{\pm }{\ell }_j^{\mp }$ decays, we introduce two triplet vectorlike leptons, $(1,3{)}_{-1}$ and $(1,3{)}_0$. The resultant branching ratio for $h\to \mu \tau$ can be up to $10^{-4}$ when the constraints from the invisible $Z$ decays are applied. As a result, the signal strength for $\tau \tau$ channel has a $12\%$ deviation from the standard model prediction, while the muon $g-2$ is two-order of magnitude smaller than the data and $BR(\tau \to \mu \gamma )$ is of order of $10^{-12}$. A predicted doubly charged lepton in $pp$ collisions at $\sqrt{s}=13$ TeV is analyzed and it is found that the interesting production channels are $pp\to ({\Psi }_1^{--}{\Psi }_1^{++},{\Psi }_1^{\pm \pm }{\Psi }_1^{\mp })$. Both single and pair production cross sections of ${\Psi }_1^{++}$ are comparable and can be a few hundred fb. The main decay channels for the doubly charged lepton are ${\Psi }^{\pm \pm }\to {\ell }^{\pm }{W}^{\pm }$ and for the heavy singly charged lepton are ${\Psi }_1^{\pm }\to \nu W^{\pm },{\ell }^{\pm }Z$. The numerical analysis is given at $13$ TeV LHC with $100$ fb${}^{-1}$ luminosity.

   hep-phhep-exEPJC(2016)·30 citations
7. 07*

   Testing the tetraquark structure for the $X$ resonances in low-lying region

   Hungchong Kim🇰🇷 · K. S. Kim🇰🇷 · Myung-Ki Cheoun🇰🇷 · Daisuke Jido🇯🇵 · Makoto Oka🇯🇵

   Assuming four-quark structure for the $X$ resonances in low-lying region, we calculate their masses using the color-spin interaction. In specific, the hyperfine masses of the color-spin interaction are calculated for the possible states in spin-0, spin-1, spin-2 channels. The two states in spin-0 channel as well as the two states in spin-1 channel are diagonalized in order to generate the physical hyperfine masses. By matching the difference in hyperfine masses with the splitting in corresponding hadron masses and using the $X(3872)$ mass as an input, we estimate the masses corresponding to the states $J^{PC}=0^{++},1^{+-},2^{++}$. We find the masses of two states in $1^{+-}$ are close to those of $X(3823)$, $X(3900)$, and the mass of the $2^{++}$ state is close to that of $X(3940)$. For them, the discrepancies are about $\sim 10$ MeV. This may suggest that the quantum numbers of the controversial states are $X(3823)=1^{+-},X(3900)=1^{+-},X(3940)=2^{++}$. In this work, we use the same inputs parameters, the constituent quark masses and the strength of the color-spin interaction, that have been adopted in the previous work on the $D$ or $B$-meson excited states. There, it was shown that the four-quark structure can be manifested in their excited states. Thus, our results in this work provide a consistent treatment on open- and hidden-charm mesons as far as the four-quark model is concerned.

   hep-phEPJA(2016)·19 citations
8. 08*

   Collider Tests of (Composite) Diphoton Resonances

   Emiliano Molinaro🇩🇰 · Francesco Sannino🇩🇰 · Natascia Vignaroli🇩🇰

   We analyze the Large Hadron Collider sensitivity to new pseudoscalar resonances decaying into diphoton with masses up to scales of few TeVs. We focus on minimal scenarios where the production mechanisms involve either photon or top-mediated gluon fusion, partially motivated by the tantalizing excess around 750 GeV reported by ATLAS and CMS. The two scenarios lead respectively to a narrow and a wide resonance. We first provide a model-independent analysis via effective operators and then introduce minimal models of composite dynamics where the diphoton channel is characterized by their topological sector. The relevant state here is the pseudoscalar associated with the axial anomaly of the new composite dynamics. If the Standard Model top mass is generated via four-fermion operators the coupling of this state to the top remarkably explains the wide-width resonance reported by ATLAS. Beyond the excess, our analysis paves the way to test dynamical electroweak symmetry breaking via topological sectors.

   hep-phhep-exhep-latNPB(2016)·25 citations
9. 09*

   Non-dipolar Wilson links for quasi-parton distribution functions

   Hsiang-nan Li🇹🇼

   We propose a modified definition for a quasi-parton distribution function (QPDF) with an equal-time correlator in the large momentum limit, whose two pieces of space-like Wilson links are oriented in orthogonal directions. It is explicitly shown at one-loop level that the linear divergence in the original QPDF with dipolar Wilson links, which complicates its matching to the standard light-cone parton distribution function (LPDF), is removed. The LPDF can then be extracted reliably from Euclidean lattice data for the QPDF with the non-dipolar Wilson links.

   hep-phPRD(2016)·52 citations
10. 10*

    Matter Power Spectrum in Hidden Neutrino Interacting Dark Matter Models: A Closer Look at the Collision Term

    Tobias Binder🇩🇪 · Laura Covi🇩🇪 · Ayuki Kamada🇺🇸 · Hitoshi Murayama🇺🇸 · Tomo Takahashi🇯🇵 · Naoki Yoshida🇯🇵

    Dark Matter (DM) models providing possible alternative solutions to the small- scale crisis of standard cosmology are nowadays of growing interest. We consider DM interacting with light hidden fermions via well motivated fundamental operators showing the resultant matter power spectrum is suppressed on subgalactic scales within a plausible parameter region. Our basic description of the evolution of cosmological perturbations relies on a fully consistent first principles derivation of a perturbed Fokker-Planck type equation, generalizing existing literature. The cosmological perturbation of the Fokker-Planck equation is presented for the first time in two different gauges, where the results transform into each other according to the rules of gauge transformation. Furthermore, our focus lies on a derivation of a broadly applicable and easily computable collision term showing important phenomenological differences to other existing approximations. As one of the main results and concerning the small-scale crisis, we show the equal importance of vector and scalar boson mediated interactions between DM and light fermions.

    hep-phastro-ph.COJCAP(2016)·83 citations
11. 11*

    Isotropic extragalactic flux from dark matter annihilations: lessons from interacting dark matter scenarios

    Ángeles Moliné (Lisbon, CFTP & Valencia U., IFIC)🇵🇹 · Jascha A. Schewtschenko (Durham U., IPPP & Durham U., ICC)🇬🇧 · Sergio Palomares-Ruiz (Valencia U., IFIC)🇪🇸 · Celine Boehm (Durham U., IPPP & Annecy, LAPTH)🇬🇧 · Carlton M. Baugh (Durham U., ICCC)🇬🇧

    The extragalactic gamma-ray and neutrino emission may have a contribution from dark matter (DM) annihilations. In the case of discrepancies between observations and standard predictions, one could infer the DM pair annihilation cross section into cosmic rays by studying the shape of the energy spectrum. So far all analyses of the extragalactic DM signal have assumed the standard cosmological model (LambdaCDM) as the underlying theory. However, there are alternative DM scenarios where the number of low-mass objects is significantly suppressed. Therefore the characteristics of the gamma-ray and neutrino emission in these models may differ from LambdaCDM as a result. Here we show that the extragalactic isotropic signal in these alternative models has a similar energy dependence to that in LambdaCDM, but the overall normalisation is reduced. The similarities between the energy spectra combined with the flux suppression could lead one to misinterpret possible evidence for models beyond LambdaCDM as being due to CDM particles annihilating with a much weaker cross section than expected.

    ↳ astro-ph.COhep-phJCAP(2016)·18 citations
12. 12*

    An Effective Field Theory Approach to the Stabilization of ${}^8$Be in a QED Plasma

    Xiaojun Yao🇺🇸 · Thomas Mehen🇺🇸 · Berndt Müller🇺🇸

    We use effective field theory to study the $\alpha$-$\alpha$ resonant scattering in a finite-temperature QED plasma. The static plasma screening effect causes the resonance state ${}^8$Be to live longer and eventually leads to the formation of a bound state when $m_D\gtrsim 0.3$ MeV. We speculate that this effect may have implications on the rates of cosmologically and astrophysically relevant nuclear reactions involving $\alpha$ particles.

    ↳ nucl-thhep-phJ.Phys.G(2016)·3 citations
13. 13*

    Is The Gamma-Ray Source 3FGL J2212.5+0703 A Dark Matter Subhalo?

    Bridget Bertoni🇺🇸 · Dan Hooper🇺🇸 · Tim Linden🇺🇸

    In a previous paper, we pointed out that the gamma-ray source 3FGL J2212.5+0703 shows evidence of being spatially extended. If a gamma-ray source without detectable emission at other wavelengths were unambiguously determined to be spatially extended, it could not be explained by known astrophysics, and would constitute a smoking gun for dark matter particles annihilating in a nearby subhalo. With this prospect in mind, we scrutinize the gamma-ray emission from this source, finding that it prefers a spatially extended profile over that of a single point-like source with 5.1 sigma statistical significance. We also use a large sample of active galactic nuclei and other known gamma-rays sources as a control group, confirming, as expected, that statistically significant extension is rare among such objects. We argue that the most likely (non-dark matter) explanation for this apparent extension is a pair of bright gamma-ray sources that serendipitously lie very close to each other, and estimate that there is a chance probability of ~2% that such a pair would exist somewhere on the sky. In the case of 3FGL J2212.5+0703, a model with a second gamma-ray point source at the location of a known BZCAT/CRATES radio source yields fits that are comparable in quality to those obtained for a single extended source. If 3FGL J2212.5+0703 is a dark matter subhalo, it would imply that dark matter particles have a mass of ~18-33 GeV and an annihilation cross section on the order of sigma v ~ 10^-26 cm^3/s (for the representative case of annihilations to bb), similar to the values required to generate the Galactic Center gamma-ray excess.

    ↳ astro-ph.HEastro-ph.COastro-ph.GAhep-phJCAP(2016)·48 citations
14. 14*

    Is the gravitational-wave ringdown a probe of the event horizon?

    Vitor Cardoso🇵🇹 · Edgardo Franzin🇮🇹 · Paolo Pani🇮🇹

    It is commonly believed that the ringdown signal from a binary coalescence provides a conclusive proof for the formation of an event horizon after the merger. This expectation is based on the assumption that the ringdown waveform at intermediate times is dominated by the quasinormal modes of the final object. We point out that this assumption should be taken with great care, and that very compact objects with a light ring will display a similar ringdown stage, even when their quasinormal-mode spectrum is completely different from that of a black hole. In other words, universal ringdown waveforms indicate the presence of light rings, rather than of horizons. Only precision observations of the late-time ringdown signal, where the differences in the quasinormal-mode spectrum eventually show up, can be used to rule out exotic alternatives to black holes and to test quantum effects at the horizon scale.

    ↳ gr-qcastro-ph.HEhep-phhep-thPRL(2016)·973 citations
15. 15*

    The Analytic Renormalization Group

    Frank Ferrari (UL Brussels, Intl. Solvay Inst., CERN)🇧🇪

    Finite temperature Euclidean two-point functions in quantum mechanics or quantum field theory are characterized by a discrete set of Fourier coefficients $G_k$, $k\in \mathbb{Z}$, associated with the Matsubara frequencies ${\nu }_k=2\pi k/\beta$. We show that analyticity implies that the coefficients $G_k$ must satisfy an infinite number of model-independent linear equations that we write down explicitly. In particular, we construct "Analytic Renormalization Group" linear maps ${\mathsf{A}}_{\mu }$ which, for any choice of cut-off $\mu$, allow to express the low energy Fourier coefficients for $|{\nu }_k|<\mu$ (with the possible exception of the zero mode $G_0$), together with the real-time correlators and spectral functions, in terms of the high energy Fourier coefficients for $|{\nu }_k|\ge \mu$. Operating a simple numerical algorithm, we show that the exact universal linear constraints on $G_k$ can be used to systematically improve any random approximate data set obtained, for example, from Monte-Carlo simulations. Our results are illustrated on several explicit examples.

    ↳ hep-latcond-mat.stat-mechhep-phhep-th+2NPB(2016)·8 citations
16. 16*

    Evidence for a $B_s^0{\pi }^{\pm }$ State

    D0 Collaboration

    We report evidence of a narrow structure, $X(5568)$, in the decay sequence $X(5568)\to B_s^0{\pi }^{\pm }$, $B_s^0\to J/\psi \varphi$, $J/\psi \to {\mu }^{+}{\mu }^{-}$, $\varphi \to K^{+}{K}^{-}$. This is evidence for the first instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be $m=5567.8\pm 2.9{(\mathrm{stat})}_{-1.9}^{+0.9}(\mathrm{syst})$ MeV/$c^2$ and $\Gamma =21.9\pm 6.4{(\mathrm{stat})}_{-2.5}^{+5.0}(\mathrm{syst})$ MeV/$c^2$. If the decay is $X(5568)\to B_s^{\ast }{\pi }^{\pm }\to B_s^0\gamma {\pi }^{\pm }$ with an unseen $\gamma$, $m(X(5568))$ will be shifted up by $m(B_s^{\ast })-m(B_s^0)\sim 49$ MeV/$c^2$. This measurement is based on $10.4\mathrm{f}{\mathrm{b}}^{-1}$ of $p\bar{p}$ collision data at $\sqrt{s}$ = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider.

    ↳ hep-exhep-phPRL(2016)·268 citations
17. 17*

    Investigation of $B\bar{B}$ four-quark systems using lattice QCD

    Antje Peters🇩🇪 · Pedro Bicudo🇵🇹 · Krzysztof Cichy🇩🇪 · Marc Wagner🇩🇪

    We investigate $B\bar{B}$ systems by computing potentials of two static quarks in the presence of two quarks of finite mass using lattice QCD. By solving the Schrödinger equation we check whether these potentials are sufficiently attractive to host bound states. Particular focus is put on the experimentally most promising bottomonium-like tetraquark candidate $Z_b^{\pm }$ with quantum numbers $I(J^P)=1(1^{+})$.

    ↳ hep-lathep-exhep-phJ.Phys.Conf.Ser.(2016)·25 citations
18. 18*

    NC plane waves, Casimir effect and flux tube potential with Lüscher terms

    Samuel Kováčik · Peter Prešnajder

    We analyze plane waves in a model of quantum mechanics in a three dimensional noncommutative (NC) space $R_{\lambda }^3$. Signature features of NC models are impossibility of probing distances smaller than a certain length scale {\lambda} and a presence of natural energetic cut-off at energy scale of order $1/{\lambda }^2$ (in convenient units). We analyze consequences of such restrictions on a 1 dimensional Casimir effect. The result shows resemblance to flux tube potential for quark-antiquark pairs and to effective bosonic string theories with Lüscher terms. Such behavior might effect the radius of possible compact (fuzzy) dimensions.

    ↳ quant-phhep-ph5 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.