Wed·Sep 14, 2016Wednesday·September 14, 2016

1. 01*

   Fixed Point and Anomaly Mediation in Partially $N=2$ Supersymmetric Standard Models

   Wen Yin🇯🇵

   Motivated by the simple toroidal compactification of extra-dimensional SUSY theories, we investigate on a partially $N=2$ supersymmetric (SUSY) extension of the standard model which has an $N=2$ SUSY sector and an $N=1$ SUSY sector. We point out that below the scale of the partially breaking of $N=2$ to $N=1$, the ratio of Yukawa to gauge couplings embedded in the original $N=2$ gauge interaction in the $N=2$ sector becomes greater due to a fixed point. Since at the partially breaking scale the sfermion masses in the $N=2$ sector is suppressed due to the $N=2$ non-renormalization theorem, the anomaly mediation effect becomes important. If dominant, the anomaly induced masses for the sfermions in the $N=2$ sector are almost UV-insensitive due to the fixed point. Interestingly, these masses are always positive, i.e. no tachyonic slepton problem. From an example model, we show interesting phenomena differing from the ordinary MSSM. In particular, the dark matter can be a sbino, i.e. the scalar component of the $N=2$ vector multiplet of $\mathrm{U}(1{)}_{\mathrm{Y}}$. To obtain the correct dark matter abundance, the mass of sbino, as well as the MSSM sparticles in the $N=2$ sector which have a typical mass pattern of anomaly mediation, is required to be small. Therefore, this scenario can be tested and confirmed in the LHC and may be further confirmed by the measurement of the $N=2$ Yukawa couplings in future colliders. This model can explain dark matter, muon $g-2$ anomaly, gauge coupling unification and relaxes some ordinary problems within the MSSM. Also, it is compatible with thermal leptogenesis.

   hep-phhep-thCPC(2018)·10 citations
2. 02*

   Testing the parton evolution with the use of two-body final states

   S.P. Baranov🇷🇺 · H. Jung🇩🇪 · A.V. Lipatov🇷🇺 · M.A. Malyshev🇷🇺

   We consider the production of $b\bar{b}$ quarks and Drell-Yan lepton pairs at LHC conditions focusing attention on the total transverse momentum of the produced pair and on the azimuthal angle between the momenta of the outgoing particles. Plotting the corresponding distributions in bins of the final state invariant mass, one can reconstruct the full map of the transverse momentum dependent parton densities in a proton. We give examples of how can these distributions can look like at the LHC energies.

   hep-phEPJC(2017)·29 citations
3. 03*

   New LUX and PandaX-II Results Illuminating the Simplest Higgs-Portal Dark Matter Models

   Xiao-Gang He🇨🇳 · Jusak Tandean🇹🇼

   Direct searches for dark matter (DM) by the LUX and PandaX-II Collaborations employing xenon-based detectors have recently come up with the most stringent limits to date on the spin-independent elastic scattering of DM off nucleons. For Higgs-portal scalar DM models, the new results have precluded any possibility of accommodating low-mass DM as suggested by the DAMA and CDMS II Si experiments utilizing other target materials, even after invoking isospin-violating DM interactions with nucleons. In the simplest model, SM+D, which is the standard model plus a real singlet scalar named darkon acting as the DM candidate, the LUX and PandaX-II limits rule out DM masses roughly from 4 to 450 GeV, except a small range around the resonance point at half of the Higgs mass where the interaction cross-section is near the neutrino-background floor. In the THDM II+D, which is the type-II two-Higgs-doublet model combined with a darkon, the region excluded in the SM+D by the direct searches can be recovered due to suppression of the DM effective interactions with nucleons at some values of the ratios of Higgs couplings to the up and down quarks, making the interactions significantly isospin-violating. However, in either model, if the 125-GeV Higgs boson is the portal between the dark and SM sectors, DM masses less than 50 GeV or so are already ruled out by the LHC constraint on the Higgs invisible decay. In the THDM II+D, if the heavier $CP$-even Higgs boson is the portal, theoretical restrictions from perturbativity, vacuum stability, and unitarity requirements turn out to be important instead and exclude much of the region below 100 GeV. For larger DM masses, the THDM II+D has plentiful parameter space that corresponds to interaction cross-sections under the neutrino-background floor and therefore is likely to be beyond the reach of future direct searches without directional sensitivity.

   hep-phastro-ph.COhep-exJHEP(2016)·66 citations
4. 04*

   Vacuum stability in an extended standard model with a leptoquark

   Priyotosh Bandyopadhyay🇮🇹 · Rusa Mandal🇮🇳

   We investigate the standard model (SM) with the extension of a charged scalar having fractional electromagnetic charge of $-1/3$ unit and with lepton and baryon number violating couplings at tree level. Without directly taking part in the electro-weak (EW) symmetry breaking, this scalar can affect stability of the EW vacuum via loop effects. The impact of such a scalar, i.e., a leptoquark on the perturbativity of SM dimensionless couplings as well as on new physics couplings has been studied at two-loop order. The vacuum stability of the Higgs potential is checked using one-loop renormalization group (RG) improved effective potential approach with two-loop beta function for all the couplings. From the stability analysis various bounds are drawn on parameter space by identifying the region corresponding to metastability and stability of the EW vacuum. Later we also address the Higgs mass fine-tuning issue via Veltman condition and the presence of such scalar increases the scale up to which the theory can be considered as reasonably fine-tuned. All these constraints give a very predictive parameter space for leptoquark couplings which can be tested at present and future colliders. Especially, a leptoquark with mass $\mathcal{O}$(TeV) can give rise to lepton-quark flavor violating signatures via decaying into the $t\tau$ channel at tree level, which can be tested at the LHC or future colliders.

   hep-phhep-exPRD(2017)·38 citations
5. 05*

   Dispersive treatment of $K_S\to \gamma \gamma$ and $K_S\to \gamma {\ell }^{+}{\ell }^{-}$

   Gilberto Colangelo🇨🇭 · Ramon Stucki🇨🇭 · Lewis C. Tunstall🇨🇭

   We analyse the rare kaon decays $K_S\to \gamma \gamma$ and $K_S\to \gamma {\ell }^{+}{\ell }^{-}$ $(\ell =e\text{mbox}or\mu )$ in a dispersive framework in which the weak Hamiltonian carries momentum. Our analysis extends predictions from lowest order $SU(3{)}_L\times SU(3{)}_R$ chiral perturbation theory ($\chi$PT${}_3$) to fully account for effects from final-state interactions, and is free from ambiguities associated with extrapolating the kaon off-shell. Given input from $K_S\to \pi \pi$ and $\gamma {\gamma }^{(\ast )}\to \pi \pi$, we solve the once-subtracted dispersion relations numerically to predict the rates for $K_S\to \gamma \gamma$ and $K_S\to \gamma {\ell }^{+}{\ell }^{-}$. In the leptonic modes, we find sizeable corrections to the $\chi$PT${}_3$ predictions for the integrated rates.

   hep-phhep-latnucl-thEPJC(2016)·16 citations
6. 06*

   Hidden Sector Hydrogen as Dark Matter: Small-scale Structure Formation Predictions and the Importance of Hyperfine Interactions

   Kimberly K. Boddy🇺🇸 · Manoj Kaplinghat🇺🇸 · Anna Kwa🇺🇸 · Annika H. G. Peter🇺🇸

   We study the atomic physics and the astrophysical implications of a model in which the dark matter is the analog of hydrogen in a secluded sector. The self interactions between dark matter particles include both elastic scatterings as well as inelastic processes due to a hyperfine transition. The self-interaction cross sections are computed by numerically solving the coupled Schrödinger equations for this system. We show that these self interactions exhibit the right velocity dependence to explain the low dark matter density cores seen in small galaxies while being consistent with all constraints from observations of clusters of galaxies. For a viable solution, the dark hydrogen mass has to be in 10--100 GeV range and the dark fine-structure constant has to be larger than 0.02. Precisely for this range of parameters, we show that significant cooling losses may occur due to inelastic excitations to the hyperfine state and subsequent decays, with implications for the evolution of low-mass halos and the early growth of supermassive black holes. Cooling from excitations to higher $n$ levels of dark hydrogen and subsequent decays is possible at the cluster scale, with a strong dependence on halo mass. Finally, we show that the minimum halo mass is in the range of $10^{3.5}$ to $10^7{M}_{\odot }$ for the viable regions of parameter space, significantly larger than the typical predictions for weakly-interacting dark matter models. This pattern of observables in cosmological structure formation is unique to this model, making it possible to rule in or rule out hidden sector hydrogen as a viable dark matter model.

   hep-phastro-ph.GAPRD(2016)·106 citations
7. 07*

   Leptogenesis and neutral gauge bosons

   Julian Heeck🇧🇪 · Daniele Teresi🇧🇪

   We consider low-scale leptogenesis via right-handed neutrinos $N$ coupled to a $Z^{\prime }$ boson, with gauged $U(1{)}_{B-L}$ as a simple realization. Keeping the neutrinos sufficiently out of equilibrium puts strong bounds on the $Z^{\prime }$ coupling strength and mass, our focus being on light $Z^{\prime }$ and $N$, testable in the near future by SHiP, HPS, Belle II, and at the LHC. We show that leptogenesis could be robustly falsified in a large region of parameter space by the double observation of $Z^{\prime }$ and $N$, e.g. in the channel $pp\to Z^{\prime }\to NN$ with displaced $N$-decay vertex, and by several experiments searching for light $Z^{\prime }$, according to the mass of $N$.

   hep-phPRD(2016)·27 citations
8. 08*

   Accidental permutation symmetries as a test for Grand Unification: the supersymmetric $SU(5)$ case

   Sylvain Fichet🇧🇷 · Björn Herrmann🇫🇷

   Unification of matter fields implies the existence of accidental permutation symmetries, which potentially remain immune to large quantum corrections up to the TeV scale. We investigate the case of a supersymmetric $SU(5)$ grand unified theory, where such a permutation symmetry is present in the up-type squark sector. We present a variety of tests allowing to challenge the $SU(5)$ hypothesis based on the observation of squarks at the LHC. These tests appear as relations among observables involving flavour-violating or chirality-flipping decays of squarks. Moreover, they rely on top-polarimetry and charm-tagging. As an example, we discuss the application to the scenario of Natural Supersymmetry, while more examples can be found in the related journal publications.

   hep-phPoS(2016)·0 citations
9. 09*

   J/P=1/2+, J/P=3/2+ masses in statistical model

   Amanpreet Kaur🇮🇳 · Alka Upadhyay🇮🇳

   The mass formulae for the baryon octet and decuplet are calculated. These formulae are function of constituent quark masses and spin spin interaction terms for the quarks inside the baryons. The coefficients in the mass formulae is estimated by the statistical model for J/P=1/2+, J/P=3/2+, incorporating the contributions from \sea" containing uu; dd; ss pairs and gluons . The measured masses are presented and found to be matching good with some of the experimental and theoretical data.

   hep-phEPJA(2016)·5 citations
10. 10*

    Hidden Local Symmetry and Beyond

    Koichi Yamawaki🇯🇵

    Gerry Brown was a godfather of our hidden local symmetry (HLS) for the vector meson from the birth of the theory throughout his life. The HLS is originated from very nature of the nonlinear realization of the symmetry G based on the manifold G/H, and thus is universal to any physics based on the nonlinear realization. Here I focus on the Higgs Lagrangian of the Standard Model (SM), which is shown to be equivalent to the nonlinear sigma model based on G/H= SU(2)_L x SU(2)_R/SU(2)_V with additional symmetry, the nonlinearly realized scale symmetry. Then the SM does have a dynamical gauge boson of the SU(2)_V HLS, "SM rho meson", in addition to the Higgs as a pseudo dilaton as well as the NG bosons to be absorbed into the W and Z. Based on the recent work done with S. Matsuzaki and H. Ohki, I discuss a novel possibility that the SM rho meson acquires kinetic term by the SM dynamics itself, which then stabilizes the skyrmion dormant in the SM as a viable candidate for the dark matter, what we call "Dark SM skyrmion (DSMS)".

    hep-phhep-thnucl-thIJMPE(2017)·18 citations
11. 11*

    Analytical $O({\alpha }_s)$ corrections to the beam frame double-spin density matrix elements of $e^{+}{e}^{-}\to t\bar{t}$

    L. Kaldamäe🇪🇪 · S. Groote🇪🇪 · J.G. Körner🇩🇪

    We provide analytical results for the $O({\alpha }_s)$ corrections to the double-spin density matrix elements in the reaction $e^{+}{e}^{-}\to t\bar{t}$. These concern the elements $ll$, $lt$, $ln$, $tt$, $tn$, and $nn$ of the double-spin density matrix elements where $l,t,n$ stand for longitudinal, transverse and normal orientations with respect to the beam frame spanned by the electron and the top quark momentum.

    hep-phPRD(2016)·4 citations
12. 12*

    Exclusive photoproduction of a $\gamma \rho$ pair with a large invariant mass

    R. Boussarie🇫🇷 · B. Pire🇫🇷 · L. Szymanowski🇵🇱 · S. Wallon🇫🇷

    Exclusive photoproduction of a $\gamma \rho$ pair in the kinematics where the pair has a large invariant mass and the final nucleon has a small transverse momentum is described in the collinear factorization framework. The scattering amplitude is calculated at leading order in ${\alpha }_s$ and the differential cross sections for the process where the $\rho -$meson is either longitudinally or transversely polarized are estimated in the kinematics of the JLab 12-GeV experiments.

    hep-phhep-exnucl-exnucl-thJHEP(2017)·80 citations
13. 13*

    $f_0(500)$, $f_0(980)$ and $a_0(980)$ production in the ${\chi }_{c1}\to \eta {\pi }^{+}{\pi }^{-}$ reaction

    Wei-Hong Liang🇨🇳 · Ju-Jun Xie🇨🇳 · E. Oset🇪🇸

    We study the ${\chi }_{c1}\to \eta {\pi }^{+}{\pi }^{-}$ decay, paying attention to the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ from the final state interaction of pairs of mesons that can lead to these three mesons in the final state, which is implemented using the chiral unitary approach. Very clean and strong signals are obtained for the $a_0(980)$ excitation in the $\eta \pi$ invariant mass distribution and for the $f_0(500)$ in the ${\pi }^{+}{\pi }^{-}$ mass distribution. A smaller, but also clear signal for the $f_0(980)$ excitation is obtained. The results are contrasted with experimental data and the agreement found is good, providing yet one more test in support of the picture where these resonances are dynamically generated from the meson-meson interaction.

    hep-phEPJC(2016)·53 citations
14. 14*

    Extraction of $t$-slopes from experimental $\gamma p\to K^{+}\Lambda$ and $\gamma p\to K^{+}{\Sigma }_0$ cross section data

    Adam Freese🇺🇸 · Daniel Puentes🇺🇸 · Shankar Adhikari🇺🇸 · Rafael Badui🇺🇸 · Lei Guo🇺🇸 · Brian Raue🇺🇸

    We analyze recent $K^{+}$ meson photoproduction data from the CLAS collaboration for the reactions $\gamma p\to K^{+}\Lambda$ and $\gamma p\to K^{+}{\Sigma }_0$, fitting measured forward-angle differential cross sections to the form $A{e}^{Bt}$. We develop a quantitative scheme for determining the kinematic region where the fit is to be done, and, from the extracted $t$-slope $B$, determine whether single-Reggeon exchange can explain the production mechanism. We find that, in the region $5<s<8.1$ GeV${}^2$, production of the $K^{+}\Lambda$ channel can be explained by single $K^{+}$ Reggeon exchange, but the $K^{+}{\Sigma }_0$ production channel cannot. We verify these conclusions by fitting the data to a differential cross section produced by the interfering sum of two exponential amplitudes.

    hep-phnucl-exPRC(2017)·1 citation
15. 15*

    Precise predictions for Dirac neutrino mixing

    Gauhar Abbas🇪🇸 · Mehran Zahiri Abyaneh🇪🇸 · Rahul Srivastava🇪🇸

    The neutrino mixing parameters are thoroughly studied using renormalization-group evolution of Dirac neutrinos with recently proposed parametrization of the neutrino mixing angles referred as `high-scale mixing relations'. The correlations among all neutrino mixing and $CP$ violating observables are investigated. The predictions for the neutrino mixing angle ${\theta }_{23}$ are precise, and could be easily tested by ongoing and future experiments. We observe that the high scale mixing unification hypothesis is incompatible with Dirac neutrinos due to updated experimental data.

    hep-phhep-exPRD(2017)·13 citations
16. 16*

    Lepton mass and mixing in a simple extension of the Standard Model based on T7 flavor symmetry

    V. V. Vien🇻🇳 · H. N. Long🇻🇳

    A simple Standard Model Extension based on $T_7$ flavor symmetry which accommodates lepton mass and mixing with non-zero ${\theta }_{13}$ and CP violation phase is proposed. At the tree- level, the realistic lepton mass and mixing pattern is derived through the spontaneous symmetry breaking by just one vacuum expectation value ($v$) which is the same as in the Standard Model. Neutrinos get small masses from one $SU(2{)}_L$ doublet and two $SU(2{)}_L$ singlets in which one being in $\underline{1}$ and the two others in $\underline{3}$ and ${\underline{3}}^{\ast }$ under $T_7$ , respectively. The model also gives a remarkable prediction of Dirac CP violation ${\delta }_{CP}=172.598^{\circ }$ in both normal and inverted hierarchies which is still missing in the neutrino mixing matrix.

    hep-phPhys.Atom.Nucl.(2019)·13 citations
17. 17*

    The 5 MeV bump - a nuclear whodunit mystery

    Patrick Huber🇺🇸

    We perform a combined analysis of recent NEOS and Daya Bay data on the reactor antineutrino spectrum. This analysis includes approximately 1.5 million antineutrino events, which is the largest neutrino event sample analyzed to date. We use a double ratio which cancels flux model dependence and related uncertainties as well as the effects of the detector response model. We find at 3-4 standard deviation significance level, that plutonium-239 and plutonium-241 are disfavored as the single source for the the so-called 5 MeV bump. This analysis method has general applicability and in particular with higher statistics data sets will be able to shed significant light on the issue of the bump. With some caveat this also should allow to improve the sensitivity for sterile neutrino searches in NEOS.

    hep-phhep-exnucl-exnucl-thPRL(2017)·88 citations
18. 18*

    Energy loss as the origin of an universal scaling law of the elliptic flow

    Carlota Andrés🇪🇸 · Mikhail Braun🇷🇺 · Carlos Pajares🇪🇸

    It is shown that the excellent scaling of the elliptic flow found for all centralities, species and energies from RHIC to the LHC for $p_T$ less than the saturation momentum is a consequence of the energy lost by a parton interacting with the color field produced in a nucleus-nucleus collision. In particular, the deduced shape of the scaling curve describes correctly all the data. We discuss the possible extensions to higher $p_T$, proton-nucleus and proton-proton collisions as well as higher harmonics.

    hep-phnucl-thEPJA(2017)·14 citations
19. 19*

    Gravitational Waves as a New Probe of Bose-Einstein Condensate Dark Matter

    P. S. Bhupal Dev🇩🇪 · Manfred Lindner🇩🇪 · Sebastian Ohmer🇩🇪

    There exists a class of ultralight Dark Matter (DM) models which could form a Bose-Einstein condensate (BEC) in the early universe and behave as a single coherent wave instead of individual particles in galaxies. We show that a generic BEC DM halo intervening along the line of sight of a gravitational wave (GW) signal could induce an observable change in the speed of GW, with the effective refractive index depending only on the mass and self-interaction of the constituent DM particles and the GW frequency. Hence, we propose to use the deviation in the speed of GW as a new probe of the BEC DM parameter space. With a multi-messenger approach to GW astronomy and/or with extended sensitivity to lower GW frequencies, the entire BEC DM parameter space can be effectively probed by our new method in the near future.

    hep-phastro-ph.COgr-qcPLB(2017)·72 citations
20. 20*

    Impact of axisymmetric mass models for dwarf spheroidal galaxies on indirect dark matter searches

    Niki Klop🇳🇱 · Fabio Zandanel🇳🇱 · Kohei Hayashi🇯🇵 · Shin'ichiro Ando🇳🇱

    Dwarf spheroidals are low-luminosity satellite galaxies of the Milky Way highly dominated by dark matter (DM). Therefore, they are prime targets to search for signals from dark matter annihilation using gamma-ray observations. While the typical assumption is that the dark matter density profile of these satellite galaxies can be described by a spherical symmetric Navarro-Frenk-White (NFW) profile, recent observational data of stellar kinematics suggest that the DM halos around these galaxies are better described by axisymmetric profiles. Motivated by such evidence, we analyse about seven years of PASS8 Fermi data for seven classical dwarf galaxies, including Draco, adopting both the widely used NFW profile and observationally-motivated axisymmetric density profiles. For four of the selected dwarfs (Sextans, Carina, Sculptor and Fornax) axisymmetric mass models suggest a cored density profile rather than the commonly adopted cusped profile. We found that upper limits on the annihilation cross section for some of these dwarfs are significantly higher than the ones achieved using an NFW profile. Therefore, upper limits in the literature obtained using spherical symmetric cusped profiles, such as the NFW, might be overestimated. Our results show that it is extremely important to use observationally motivated density profiles going beyond the usually adopted NFW in order to obtain accurate constraints on the dark matter annihilation cross section.

    ↳ astro-ph.COastro-ph.HEhep-phPRD(2017)·33 citations
21. 21*

    Is the spin connection confined or condensed?

    John F. Donoghue🇺🇸

    The spin connection enters the theory of gravity as a nonabelian gauge field associated with local Lorentz transformations. Normally it is eliminated from making an extra assumption - that of the metricity of the vierbein field. However, treated by itself with the usual gauge action, it has a negative beta function, implying that it is asymptotically free. I suggest that the spin connection could be confined (or perhaps partially confined) in the same way as other nonabelian gauge fields. This would remove the need to make the extra assumption of metricity, as the spin connection would not be present in the low energy theory, leaving the symmetry to be realized only using metric variables.

    ↳ hep-thgr-qchep-lathep-phPRD(2017)·29 citations
22. 22*

    A conformal model of gravitons

    John F. Donoghue🇺🇸

    In the description of general covariance, the vierbein and the Lorentz connection can be treated as independent fundamental fields. With the usual gauge Lagrangian, the Lorentz connection is characterized by an asymptotically free running coupling. When running from high energy, the coupling gets large at a scale which can be called the Planck mass. If the Lorentz connection is confined at that scale, the low energy theory can have the Einstein Lagrangian induced at low energy through dimensional transmutation. However, in general there will be new divergences in such a theory and the Lagrangian basis should be expanded. I construct a conformally invariant model with a larger basis size which potentially may have the same property.

    ↳ hep-thgr-qchep-phPRD(2017)·25 citations
23. 23*

    Propagating q-field and q-ball solution

    F.R. Klinkhamer🇩🇪 · G.E. Volovik🇫🇮

    One possible solution of the cosmological constant problem involves a so-called $q$-field, which self-adjusts so as to give a vanishing gravitating vacuum energy density (cosmological constant) in equilibrium. We show that this $q$-field can manifest itself in other ways. Specifically, we establish a propagating mode ($q$-wave) in the nontrivial vacuum and find a particular soliton-type solution in flat spacetime, which we call a $q$-ball by analogy with the well-known $Q$-ball solution. Both $q$-waves and $q$-balls are expected to play a role for the equilibration of the $q$-field in the very early universe.

    ↳ hep-thcond-mat.otherhep-phMod.Phys.Lett.A(2017)·15 citations
24. 24*

    On the Gravitational Wave Background from Black Hole Binaries after the First LIGO Detections

    Ilias Cholis🇺🇸

    The detection of gravitational waves from the merger of binary black holes by the LIGO Collaboration has opened a new window to astrophysics. With the sensitivities of ground based detectors in the coming years we can only detect the local black hole binary mergers. The integrated merger rate can instead be probed by the gravitational-wave background, the incoherent superposition of the released energy in gravitational waves during binary-black-hole coalescence. Through that, the properties of the binary black holes can be studied. In this work we show that by measuring the energy density ${\Omega }_{GW}$ (in units of the cosmic critical density) of the gravitational-wave background, we can search for the rare $\sim 100M_{\odot }$ massive black holes formed in the Universe. In addition, we can answer how often the least massive BHs of mass $>3M_{\odot }$ form. Finally, if there are multiple channels for the formation of binary black holes and if any of them predicts a narrow mass range for the black holes, then the gravitational-wave-background spectrum may have features that with the future Einstein Telescope can be detected.

    ↳ astro-ph.HEastro-ph.COhep-phJCAP(2017)·31 citations
25. 25*

    Partially Acoustic Dark Matter, Interacting Dark Radiation, and Large Scale Structure

    Zackaria Chacko🇺🇸 · Yanou Cui🇺🇸 · Sungwoo Hong🇺🇸 · Takemichi Okui🇺🇸 · Yuhsin Tsai🇺🇸

    The standard paradigm of collisionless cold dark matter is in tension with measurements on large scales. In particular, the best fit values of the Hubble rate $H_0$ and the matter density perturbation ${\sigma }_8$ inferred from the cosmic microwave background seem inconsistent with the results from direct measurements. We show that both problems can be solved in a framework in which dark matter consists of two distinct components, a dominant component and a subdominant component. The primary component is cold and collisionless. The secondary component is also cold, but interacts strongly with dark radiation, which itself forms a tightly coupled fluid. The growth of density perturbations in the subdominant component is inhibited by dark acoustic oscillations due to its coupling to the dark radiation, solving the ${\sigma }_8$ problem, while the presence of tightly coupled dark radiation ameliorates the $H_0$ problem. The subdominant component of dark matter and dark radiation continue to remain in thermal equilibrium until late times, inhibiting the formation of a dark disk. We present an example of a simple model that naturally realizes this scenario in which both constituents of dark matter are thermal WIMPs. Our scenario can be tested by future stage-IV experiments designed to probe the CMB and large scale structure.

    ↳ astro-ph.COhep-phJHEP(2016)·123 citations
26. 26*

    Relativistic axions from collapsing Bose stars

    D.G. Levkov🇷🇺 · A.G. Panin🇷🇺 · I.I. Tkachev🇷🇺

    The substructures of light bosonic (axion-like) dark matter may condense into compact Bose stars. We study collapses of the critical-mass stars caused by attractive self-interaction of the axion-like particles and find that these processes proceed in an unexpected universal way. First, nonlinear self-similar evolution (called "wave collapse" in condensed matter physics) forces the particles to fall into the star center. Second, interactions in the dense center create an outgoing stream of mildly relativistic particles which carries away an essential part of the star mass. The collapse stops when the star remnant is no longer able to support the self-similar infall feeding the collisions. We shortly discuss possible astrophysical and cosmological implications of these phenomena.

    ↳ astro-ph.COhep-phPRL(2017)·190 citations
27. 27*

    Basis Tensor Gauge Theory

    Daniel J. H. Chung🇺🇸 · Ran Lu🇺🇸

    We reformulate gauge theories in analogy with the vierbein formalism of general relativity. More specifically, we reformulate gauge theories such that their gauge dynamical degrees of freedom are local fields that transform linearly under the dual representation of the charged matter field. These local fields, which naively have the interpretation of non-local operators similar to Wilson lines, satisfy constraint equations. A set of basis tensor fields are used to solve these constraint equations, and their field theory is constructed. A new local symmetry in terms of the basis tensor fields is used to make this field theory local and maintain a Hamiltonian that is bounded from below. The field theory of the basis tensor fields is what we call the basis tensor gauge theory.

    ↳ hep-thgr-qchep-phmath-ph+1PRD(2016)·3 citations
28. 28*

    Collisions of Small Nuclei in the Thermal Model

    J. Cleymans🇿🇦 · B. Hippolyte🇫🇷 · H. Oeschler🇩🇪 · K. Redlich🇵🇱 · N. Sharma🇮🇳

    An analysis is presented of the expectations of the thermal model for particle production in collisions of small nuclei. The maxima observed in particle ratios of strange particles to pions as a function of beam energy in heavy ion collisions, are reduced when considering smaller nuclei. Of particular interest is the $\Lambda /{\pi }^{+}$ ratio shows the strongest maximum which survives even in collisions of small nuclei.

    ↳ nucl-thhep-phActa Phys.Polon.Supp.(2017)·0 citations
29. 29*

    Light-Front spin-dependent Spectral Function and Nucleon Momentum Distributions for a Three-Body System

    Alessio Del Dotto🇮🇹 · Emanuele Pace🇮🇹 · Giovanni Salmè🇮🇹 · Sergio Scopetta🇮🇹

    Poincare' covariant definitions for the spin-dependent spectral function and for the momentum distributions within the light-front Hamiltonian dynamics are proposed for a three-fermion bound system, starting from the light-front wave function of the system. The adopted approach is based on the Bakamjian-Thomas construction of the Poincare' generators, that allows one to easily import the familiar and wide knowledge on the nuclear interaction into a light-front framework. The proposed formalism can find useful applications in refined nuclear calculations, like the ones needed for evaluating the EMC effect or the semi-inclusive deep inelastic cross sections with polarized nuclear targets, since remarkably the light-front unpolarized momentum distribution by definition fulfills both normalization and momentum sum rules. It is also shown a straightforward generalization of the definition of the light-front spectral function to an A-nucleon system.

    ↳ nucl-thhep-phPRC(2017)·25 citations
30. 30*

    $\varphi$ meson self-energy in nuclear matter from $\varphi N$ resonant interactions

    D. Cabrera🇪🇸 · A. N. Hiller Blin🇪🇸 · M. J. Vicente Vacas🇪🇸

    The $\varphi$-meson properties in cold nuclear matter are investigated by implementing resonant $\varphi N$ interactions as described in effective approaches including the unitarization of scattering amplitudes. Several $N^{\ast }$-like states are dynamically generated in these models around $2$ GeV, in the vicinity of the $\varphi N$ threshold. We find that both these states and the non-resonant part of the amplitude contribute sizably to the $\varphi$ collisional self-energy at finite nuclear density. These contributions are of a similar strength as the widely studied medium effects from the $\bar{K}K$ cloud. Depending on model details (position of the resonances and strength of the coupling to $\varphi N$) we report a $\varphi$ broadening up to about $40$-$50$ MeV, to be added to the $\varphi \to \bar{K}K$ in-medium decay width, and an attractive optical potential at threshold up to about $35$ MeV at normal matter density. The $\varphi$ spectral function develops a double peak structure as a consequence of the mixing of resonance-hole modes with the $\varphi$ quasi-particle peak. The former results point in the direction of making up for missing absorption as reported in $\varphi$ nuclear production experiments.

    ↳ nucl-thhep-phPRC(2017)·39 citations
31. 31*

    A high-resolution CMOS imaging detector for the search of neutrinoless double $\beta$ decay in ${}^{82}$Se

    A.E. Chavarria🇺🇸 · C. Galbiati🇺🇸 · X. Li🇺🇸 · J.A. Rowlands🇨🇦

    We introduce high-resolution solid-state imaging detectors for the search of neutrinoless double $\beta$ decay. Based on the present literature, imaging devices from amorphous ${}^{82}$Se evaporated on a complementary metal-oxide-semiconductor (CMOS) active pixel array could have the energy and spatial resolution to produce two-dimensional images of ionizing tracks of utmost quality, effectively akin to an electronic bubble chamber in the double $\beta$ decay energy regime. Still to be experimentally demonstrated, a detector consisting of a large array of these devices could have very low backgrounds, possibly reaching $10^{-7}$/(kg y) in the neutrinoless decay region of interest (ROI), as it may be required for the full exploration of the neutrinoless double $\beta$ decay parameter space in the most unfavorable condition of a strongly quenched nucleon axial coupling constant.

    ↳ physics.ins-dethep-exhep-phnucl-exJINST(2017)·17 citations
32. 32*

    Hadron Spectroscopy, exotics and $B_c^{+}$ physics at LHCb

    Biplab Dey🇮🇹

    The LHCb experiment is designed to study properties and decays of heavy flavored hadrons produced from $pp$ collisions at the LHC. During Run~1, it has recorded the world's largest data sample of beauty and charm hadrons, enabling precision spectroscopy studies of such particles. Several important results obtained by LHCb, such as the discovery of the first pentaquark states and the first unambiguous determination of the $Z_c(4430{)}^{-}$ as an exotic state, have dramatically increased the interest on spectroscopy of heavy hadrons. An overview of the latest LHCb results on the subject, including the discovery of four strange exotic states decaying as $X\to J/\psi \varphi$, is presented. LHCb has also made significant contributions to the field of $B_c^{+}$ physics, the lowest bound state of the heavy flavor $\bar{b}$ and $c$ quarks. A synopsis of the the latest results is given.

    ↳ hep-exhep-phJ.Phys.Conf.Ser.(2016)·1 citation
33. 33*

    A proposed very high energy electron-proton collider, VHEeP

    M. Wing🇬🇧 · A. Caldwell🇩🇪

    The possibility of using plasma wakefield acceleration to build a very high energy electron-proton (VHEeP) collider at a centre-of-mass energy of 9 TeV was presented at the DIS2015 workshop. In this talk, the physics case was further developed and the idea has since been published as a journal paper. A brief summary is here given along with some details of the technical aspects not covered in the paper, which focused on the physics motivation. It is demonstrated that an $ep$ collider with a centre-of-mass energy a factor of 30 above HERA has sensitivity to new physical phenomena.

    ↳ physics.acc-phhep-exhep-phPoS(2016)·0 citations
34. 34*

    Multi-Wavelength Polarimetry and Spectral Study of M87 Jet During 2002-2008

    Sayali S. Avachat · Eric S. Perlman · Steven C. Adams · Mihai Cara · Frazer Owen · William B. Sparks · Markos Georganopoulos

    We present a multi-wavelength polarimetric and spectral study of M87 jet obtained at sub- arcsecond resolution between 2002 and 2008. The observations include multi-band archival VLA polarimetry data sets along with the HST imaging polarimetry. These observations have better angular resolution than previous work by factors of 2-3 and in addition, allow us to explore the time domain. These observations envelope the huge flare in HST-1 located at 0."86 from the nucleus (Cheung et al. 2007; Harris et al. 2009; Madrid 2009; Perlman et al. 2011). The increased resolution enables us to view more structure in each knot, showing several resolved sub-components. We also see apparent helical structure in the polarization vectors in several knots, with polarization vectors turning either clockwise or counterclockwise near the flux maxima in various places as well as show filamentary undulations. Some of these characteristics are correlated with flux and polarization maxima while others are not. We also examine the total flux and fractional polarization and look for changes in both radio and optical since the observations of Perlman et al. (1999) and test them against various models based on shocks and instabilities in the jet. Our results are broadly consistent with previous spine-sheath models and recollimation shock models, however, they require additional combinations of features to explain the observed complexity, e.g. shearing of magnetic field lines near the jet surface and compression of the toroidal component near shocks. In particular, in many regions we find apparently helical features both in total flux and polarization. We discuss the physical interpretation of these features.

    ↳ astro-ph.HEhep-phApJ(2016)·23 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.