Wed·Apr 19, 2017Wednesday·April 19, 2017

1. 01*

   Solving The Muon g-2 Anomaly With Natural NMSSM From Generalized Deflected AMSB

   Xuyang Ning🇨🇳 · Fei Wang🇨🇳

   We propose to realize (natural) NMSSM spectrum from deflected AMSB with new messenger-matter interactions. With additional messenger-matter interactions involving $10\oplus \overline{10}$ representation messengers, the muon g-2 anomaly can be solved at $2\sigma$ (or $3\sigma$) level with the corresponding gluino mass range $2.8\mathrm{TeV}<m_{\tilde{g}}<5.4\mathrm{TeV}$ (or $2.6\mathrm{TeV}<m_{\tilde{g}}<7.3\mathrm{TeV}$). Besides, our scenario is fairly natural within which the involved fine tuning can be as low as 47. So, in the framework of AMSB-type scenarios, NMSSM can be advantageous in explaining the muon g-2 anomaly in compare with MSSM.

   hep-phJHEP(2017)·25 citations
2. 02*

   Black Hole Superradiance Signatures of Ultralight Vectors

   Masha Baryakhtar🇨🇦 · Robert Lasenby🇨🇦 · Mae Teo🇺🇸

   The process of superradiance can extract angular momentum and energy from astrophysical black holes (BHs) to populate gravitationally-bound states with an exponentially large number of light bosons. We analytically calculate superradiant growth rates for vectors around rotating BHs in the regime where the vector Compton wavelength is much larger than the BH size. Spin-1 bound states have superradiance times as short as a second around stellar BHs, growing up to a thou- sand times faster than their spin-0 counterparts. The fast rates allow us to use measurements of rapidly spinning BHs in X-ray binaries to exclude a wide range of masses for weakly-coupled spin-1 particles, $5\times 10^{-14}-2\times 10^{-11}$ eV; lighter masses in the range $6\times 10^{-20}-2\times 10^{-17}$ eV start to be constrained by supermassive BH spin measurements at a lower level of confidence. We also explore routes to detection of new vector particles possible with the advent of gravitational wave (GW) astronomy. The LIGO-Virgo collaboration could discover hints of a new light vector particle in statistical analyses of masses and spins of merging BHs. Vector annihilations source continuous monochromatic gravitational radiation which could be observed by current GW observatories. At design sensitivity, Advanced LIGO may measure up to thousands of annihilation signals from within the Milky Way, while hundreds of BHs born in binary mergers across the observable universe may superradiate vector bound states and become new beacons of monochromatic gravitational waves.

   hep-phastro-ph.COastro-ph.HEgr-qcPRD(2017)·370 citations
3. 03*

   Comment on "The MSR Mass and the $\mathcal{O}({\Lambda }_{\mathrm{QCD}})$ Renormalon Sum Rule"

   Antonio Pineda🇪🇸

   In this note we confront the research conducted in \cite{Hoang:2017suc} with results previously obtained by the author, and critically examine some of their claimed findings.

   hep-ph5 citations
4. 04*

   Coherent helicity amplitude for sequential decays

   Hong Chen🇨🇳 · Rong-Gang Ping🇨🇳

   We present a derivation of coherent helicity amplitudes for a particle decaying into multifinal states with nonzero spins. The results show that the coherent amplitudes introduce additional rotations to transform the helicities into a consistent helicity system, which allows us to add helicity amplitudes for different decay chains coherently. These rotations may have significant effects on the interference between the decay chains in the partial wave analysis.

   hep-phhep-exPRD(2017)·18 citations
5. 05*

   Axion-Like Particles and Recent Observations of the Cosmic Infrared Background Radiation

   Kazunori Kohri🇯🇵 · Hideo Kodama🇯🇵

   The CIBER collaboration released their first observational data of the Cosmic IR background (CIB) radiation, which has significant excesses at around the wavelength $\sim$ 1 $\mu$m compared to theoretically-inferred values. The amount of the CIB radiation has a significant influence on the opaqueness of the Universe for TeV gamma-rays emitted from distant sources such as AGNs. With the value of CIB radiation reported by the CIBER experiment, through the reaction of such TeV gamma-rays with the CIB photons, the TeV gamma-rays should be significantly attenuated during propagation, which would lead to energy spectra in disagreement with current observations of TeV gamma ray sources. In this article, we discuss a possible resolution of this tension between the TeV gamma-ray observations and the CIB data in terms of axion [or Axion-Like Particles (ALPs)] that may increase the transparency of the Universe by the anomaly-induced photon-axion mixing. We find a region in the parameter space of the axion mass, $m_a\sim 7\times 10^{-10}-5\times 10^{-8}$eV, and the axion-photon coupling constant, $1.2\times 10^{-11}{\mathrm{GeV}}^{-1}\lesssim g_{a\gamma }\lesssim 8.8\times 10^{-10}{\mathrm{GeV}}^{-1}$ that solves this problem.

   hep-phastro-ph.COastro-ph.GAastro-ph.HE+1PRD(2017)·94 citations
6. 06*

   Asymmetric Dark Matter and the hadronic spectra of hidden QCD

   Stephen J. Lonsdale🇦🇺 · Martine Schroor🇳🇱 · Raymond R. Volkas🇦🇺

   The idea that dark matter may be a composite state of a hidden nonabelian gauge sector has received great attention in recent years. Frameworks such as asymmetric dark matter motivate the idea that dark matter may have similar mass to the proton, while mirror matter and $G\times G$ grand unified theories provide rationales for additional gauge sectors which may have minimal interactions with standard model particles. In this work we explore the hadronic spectra that these dark QCD models can allow. The effects of the number of light colored particles and the value of the confinement scale on the lightest stable state, the dark matter candidate, are examined in the hyperspherical constituent quark model for baryonic and mesonic states.

   hep-phPRD(2017)·46 citations
7. 07*

   High-Energy Vacuum Birefringence and Dichroism in an Ultrastrong Laser Field

   Sergey Bragin🇩🇪 · Sebastian Meuren🇩🇪 · Christoph H. Keitel🇩🇪 · Antonino Di Piazza🇩🇪

   A long-standing prediction of quantum electrodynamics, yet to be experimentally observed, is the interaction between real photons in vacuum. As a consequence of this interaction, the vacuum is expected to become birefringent and dichroic if a strong laser field polarizes its virtual particle--antiparticle dipoles. Here, we derive how a generally polarized probe photon beam is influenced by both vacuum birefringence and dichroism in a strong linearly polarized plane-wave laser field. Furthermore, we consider an experimental scheme to measure these effects in the nonperturbative high-energy regime, where the Euler-Heisenberg approximation breaks down. By employing circularly polarized high-energy probe photons, as opposed to the conventionally considered linearly polarized ones, the feasibility of quantitatively confirming the prediction of nonlinear QED for vacuum birefringence at the $5\sigma$ confidence level on the time scale of a few days is demonstrated for upcoming 10 PW laser systems. Finally, dichroism and anomalous dispersion in vacuum are shown to be accessible at these facilities.

   hep-phPRL(2017)·96 citations
8. 08*

   Reexamining the photon polarization in $B\to K\pi \pi \gamma$

   Michael Gronau🇮🇱 · Dan Pirjol🇷🇴

   We reexamine, update and extend a suggestion we made fifteen years ago for measuring the photon polarization in $b\to s\gamma$ by observing in $B\to K\pi \pi \gamma$ an asymmetry of the photon with respect to the $K\pi \pi$ plane. Asymmetries are calculated for different charged final states due to intermediate $K_1(1400)$ and $K_1(1270)$ resonant states. Three distinct interference mechanisms are identified contributing to asymmetries at different levels for these two kaon resonances. For $K_1(1400)$ decays including a final state ${\pi }^0$ an asymmetry around $+30\%$ is calculated, dominated by interference of two intermediate $K^{\ast }\pi$ states, while an asymmetry around $+10\%$ in decays including final ${\pi }^{+}{\pi }^{-}$ is dominated by interference of $S$ and $D$ wave $K^{\ast }\pi$ amplitudes. In decays via $K_1(1270)$ to final states including a ${\pi }^0$ a negative asymmetry is favored up to $-10\%$ if one assumes $S$ wave dominance in decays to $K^{\ast }\pi$ and $K\rho$, while in decays involving ${\pi }^{+}{\pi }^{-}$ the asymmetry can vary anywhere in the range $-13\%$ to $+24\%$ depending on unknown phases. For more precise asymmetry predictions in the latter decays we propose studying phases in $K_1\to K^{\ast }\pi ,K\rho$ by performing dedicated amplitude analyses of $B\to J/\psi ({\psi }^{\prime })K\pi \pi$. In order to increase statistics in studies of $B\to K\pi \pi \gamma$ we suggest using isospin symmetry to combine in the same analysis samples of charged and neutral $B$ decays.

   hep-phhep-exPRD(2017)·13 citations
9. 09*

   Probing minimal SUSY scenarios in the light of muon $g-2$ and dark matter

   Motoi Endo🇯🇵 · Koichi Hamaguchi🇯🇵 · Sho Iwamoto🇮🇱 · Keisuke Yanagi🇯🇵

   We study supersymmetric (SUSY) models in which the muon $g-2$ discrepancy and the dark matter relic abundance are simultaneously explained. The muon $g-2$ discrepancy, or a 3$\sigma$ deviation between the experimental and theoretical results of the muon anomalous magnetic moment, can be resolved by SUSY models, which implies at least three SUSY multiplets have masses of $\mathcal{O}(100)\mathrm{GeV}$. In particular, models with the bino, higgsino and slepton having $\mathcal{O}(100)\mathrm{GeV}$ masses are not only capable to explain the muon $g-2$ discrepancy but naturally contains the neutralino dark matter with the observed relic abundance. We study constraints and future prospects of such models; in particular, we find that the LHC search for events with two hadronic taus and missing transverse momentum can probe this scenario through chargino/neutralino production. It is shown that almost all the parameter space of the scenario can be probed at the high-luminosity LHC, and a large part can also be tested at the XENON1T experiment as well as at the ILC.

   hep-phJHEP(2017)·35 citations
10. 10*

    Associated heavy quarks pair production with Higgs as a tool for a search for non-perturbative effects of the electroweak interaction at the LHC

    B.A. Arbuzov🇷🇺 · I.V. Zaitsev🇷🇺

    Assuming an existence of an anomalous triple electro-weak bosons interaction being defined by coupling constant $\lambda$, we calculate its contribution to interactions of the Higgs with pairs of heavy particles. Bearing in mind experimental restrictions $-0.011<\lambda <0.011$ we present results for possible effects in processes $pp\to W^{+}{W}^{-}H,pp\to W^{+}ZH,pp\to W^{-}ZH,pp\to \bar{t}tH$, $pp\to \bar{b}bH$. Effects could be significant with negative sign of $\lambda$ in associated heavy quarks $t,b$ pairs production with the Higgs. In calculations we rely on results of the non-perturbative approach to a spontaneous generation of effective interactions, which defines the form-factor of the three-boson anomalous interaction.

    hep-phhep-exPLB(2017)·5 citations
11. 11*

    Thermal effects on $\rho$ meson properties in an external magnetic field

    Snigdha Ghosh🇮🇳 · Arghya Mukherjee🇮🇳 · Mahatsab Mandal🇮🇳 · Sourav Sarkar🇮🇳 · Pradip Roy🇮🇳

    A detailed study of the analytic structure of 1-loop self energy graphs for neutral and charged $\rho$ mesons is presented at finite temperature and arbitrary magnetic field using the real time formalism of thermal field theory. The imaginary part of the self energy is obtained from the discontinuities of these graphs across the Unitary and Landau cuts, which is seen to be different for ${\rho }^0$ and ${\rho }^{\pm }$. The magnetic field dependent vacuum contribution to the real part of the self energy, which is usually ignored, is found to be appreciable. A significant effect of temperature and magnetic field is seen in the self energy, spectral function, effective mass and dispersion relation of ${\rho }^0$ as well as of ${\rho }^{\pm }$ relative to its trivial Landau shift. However, for charged $\rho$ mesons, on account of the dominance of the Landau term, the effective mass appears to be independent of temperature. The trivial coupling of magnetic moment of ${\rho }^{\pm }$ with external magnetic field, when incorporated in the calculation, makes the ${\rho }^{\pm }$ to condense at high magnetic field.

    hep-phnucl-thPRD(2017)·40 citations
12. 12*

    Patterns of New Physics in $b\to s{\ell }^{+}{\ell }^{-}$ transitions in the light of recent data

    Bernat Capdevila🇪🇸 · Andreas Crivellin🇨🇭 · Sébastien Descotes-Genon🇫🇷 · Joaquim Matias🇪🇸 · Javier Virto🇨🇭

    In the Standard Model (SM), the rare transitions where a bottom quark decays into a strange quark and a pair of light leptons exhibit a potential sensitivity to physics beyond the SM. In addition, the SM embeds Lepton Flavour Universality (LFU), leading to almost identical probabilities for muon and electron modes. The LHCb collaboration discovered a set of deviations from the SM expectations in decays to muons and also in ratios assessing LFU. Other experiments (Belle, ATLAS, CMS) found consistent measurements, albeit with large error bars. We perform a global fit to all available $b\to s{\ell }^{+}{\ell }^{-}$ data ($\ell =e,\mu$) in a model-independent way allowing for different patterns of New Physics. For the first time, the NP hypothesis is preferred over the SM by $5\sigma$ in a general case when NP can enter SM-like operators and their chirally-flipped partners. LFU violation is favoured with respect to LFU at the 3-4$\sigma$ level. We discuss the impact of LFU-violating New Physics on the observable $P_5^{\prime }$ from $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ and we compare our estimate for long-distance charm contributions with an empirical model recently proposed by a group of LHCb experimentalists. Finally, we discuss NP models able to describe this consistent pattern of deviations.

    hep-phhep-exJHEP(2018)·510 citations
13. 13*

    WIMP miracle of the second kind

    Matti Heikinheimo🇫🇮 · Tommi Tenkanen🇬🇧 · Kimmo Tuominen🇫🇮

    We study dark matter production in scenarios where a scale invariant hidden sector interacts with the Standard Model degrees of freedom via a Higgs portal $\lambda {\Phi }^{†}\Phi s^2$. If the hidden sector is very weakly coupled to the SM but exhibits strong interactions within its own particle species, the dark matter abundance may arise as a result of a dark freeze-out occurring in the hidden sector. Because of scale invariance, the free parameters in the hidden sector are determined and the dark matter candidate exhibits a 'WIMP miracle of the second kind'. Demonstrating the predictive power of scale invariance, we carry out thorough analysis of dark matter production in several benchmark scenarios where the hidden sector contains either a scalar, fermion (sterile neutrino), or vector dark matter, and discuss the observational consequences of these scenarios.

    hep-phastro-ph.COPRD(2017)·62 citations
14. 14*

    Mass spectrum of spin-1/2 pentaquarks with a $c\bar{c}$ component and their anticipated discovery modes in $b$-baryon decays

    Ahmed Ali🇩🇪 · Ishtiaq Ahmed🇵🇰 · M. Jamil Aslam🇵🇰 · Abdur Rehman🇵🇰

    The LHCb discovery of the two baryonic states $P_c^{+}(4380)$ and $P_c^{+}(4450)$, having $J^P=3/2^{-}$ and $J^P=5/2^{+}$, respectively, in the process $pp\to b\bar{b}\to {\Lambda }_{b}X$, followed by the decay ${\Lambda }_b\to J/\psi p{K}^{-}$, has motivated a number of theoretical models. Interpreting them as compact $\{\bar{c}[cu][ud];L_{\mathcal{P}}=0,1\}$ objects, the mass spectroscopy of the $J^P=3/2^{-}$ and $J^P=5/2^{+}$ pentaquarks was worked out by us for the pentaquarks in the $SU(3{)}_F$ multiplets, using an effective Hamiltonian based on constituent diquarks and quarks. Their possible discovery modes in $b$-baryon decays were also given using the heavy quark spin symmetry. In this paper, we calculate the mass spectrum of the hidden $c\bar{c}$ pentaquarks having $J^P={\frac{1}{2}}^{\pm }$ for the $SU(3{)}_F$ multiplets and their anticipated discovery modes in $b$-baryon decays. Some of the $P_c^{+}(J^P=1/2^{\pm }$) pentaquarks, produced in the ${\Lambda }_b$ decays may have their masses just below the $J/\psi p$ threshold, in which case they should be searched for in the modes $P_c^{+}(J^P=1/2^{\pm })\to {\eta }_{c}p,{\mu }^{+}{\mu }^{-}p,e^{+}{e}^{-}p$.

    hep-phhep-ex7 citations
15. 15*

    Universality regained: Kibble-Zurek dynamics, off-equilibrium scaling and the search for the QCD critical point

    Swagato Mukherjee🇺🇸 · Raju Venugopalan🇺🇸 · Yi Yin🇺🇸

    We generalize and apply the key elements of the Kibble-Zurek framework of nonequilibrium phase transitions to study the non-equilibrium critical cumulants near the QCD critical point. We demonstrate the off-equilibrium critical cumulants are expressible as universal scaling functions. We discuss how to use off-equilibrium scaling to provide powerful model-independent guidance in searches for the QCD critical point.

    hep-phnucl-thNPA(2017)·7 citations
16. 16*

    Interpreting Hints for Lepton Flavor Universality Violation

    Wolfgang Altmannshofer🇺🇸 · Peter Stangl🇩🇪 · David M. Straub🇩🇪

    We interpret the recent hints for lepton flavor universality violation in rare $B$ meson decays. Based on a model-independent effective Hamiltonian approach, we determine regions of new physics parameter space that give a good description of the experimental data on $R_K$ and $R_{K^{\ast }}$, which is in tension with Standard Model predictions. We suggest further measurements that can help narrowing down viable new physics explanations. We stress that the measured values of $R_K$ and $R_{K^{\ast }}$ are fully compatible with new physics explanations of other anomalies in rare $B$ meson decays based on the $b\to s\mu \mu$ transition. If the hints for lepton flavor universality violation are first signs of new physics, perturbative unitarity implies new phenomena below a scale of $\sim 100$ TeV.

    hep-phhep-exPRD(2017)·327 citations
17. 17*

    Flavour anomalies after the $R_{K^{\ast }}$ measurement

    Guido D'Amico🇨🇭 · Marco Nardecchia🇨🇭 · Paolo Panci🇨🇭 · Francesco Sannino🇩🇰 · Alessandro Strumia🇨🇭 · Riccardo Torre🇨🇭 · Alfredo Urbano🇨🇭

    The LHCb measurement of the $\mu /e$ ratio $R_{K^{\ast }}$ indicates a deficit with respect to the Standard Model prediction, supporting earlier hints of lepton universality violation observed in the $R_K$ ratio. We show that the $R_K$ and $R_{K^{\ast }}$ ratios alone constrain the chiralities of the states contributing to these anomalies, and we find deviations from the Standard Model at the $4\sigma$ level. This conclusion is further corroborated by hints in the theoretically challenging $b\to s{\mu }^{+}{\mu }^{-}$ distributions. Theoretical interpretations in terms of $Z^{\prime }$, lepto-quarks, loop mediators, and composite dynamics are discussed. We highlight their distinctive features in terms of chiralities and flavour structure relevant for the observed anomalies.

    hep-phJHEP(2017)·332 citations
18. 18*

    $R_K$ and $R_{K^{\ast }}$ beyond the Standard Model

    Gudrun Hiller🇩🇪 · Ivan Nisandzic🇩🇪

    Measurements of the ratio of $B\to K^{\ast }\mu \mu$ to $B\to K^{\ast }ee$ branching fractions, $R_{K^{\ast }}$, by the LHCb collaboration strengthen the hints from previous studies with pseudoscalar kaons, $R_K$, for the breakdown of lepton universality, and therefore the Standard Model (SM), to $\sim 3.5\sigma$. Complementarity between $R_K$ and $R_{K^{\ast }}$ allows to pin down the Dirac structure of the new contributions to be predominantly SM-like chiral, with possible admixture of chirality-flipped contributions of up to $\mathcal{O}(\text{mbox}few10\%)$. Scalar and vector leptoquark representations $(S_3,V_1,V_3)$ plus possible (${\tilde{S}}_2,V_2$) admixture can explain $R_{K,K^{\ast }}$ via tree level exchange. Flavor models naturally predict leptoquark masses not exceeding a few TeV, with couplings to third generation quarks at $O(0.1)$, implying that this scenario can be directly tested at the LHC.

    hep-phPRD(2017)·261 citations
19. 19*

    Towards the discovery of new physics with lepton-universality ratios of $b\to s\ell \ell$ decays

    Li-Sheng Geng🇨🇳 · Benjamín Grinstein🇺🇸 · Sebastian Jäger🇬🇧 · Jorge Martin Camalich🇨🇭 · Xiu-Lei Ren🇨🇳 · Rui-Xiang Shi🇨🇳

    Tests of lepton-universality as rate ratios in $b\to s\ell \ell$ transitions can be predicted very accurately in the Standard Model. The deficits with respect to expectations reported by the LHCb experiment in muon-to-electron ratios of the $B\to K^{(\ast )}\ell \ell$ decay rates thus point to genuine manifestations of lepton non-universal new physics. In this paper, we analyse these measurements in the context of effective field theory. First, we discuss the interplay of the different operators in $R_K$ and $R_{K^{\ast }}$ and provide predictions for $R_{K^{\ast }}$ in the Standard Model and in new-physics scenarios that can explain $R_K$. We also provide approximate numerical formulas for these observables in bins of interest as functions of the relevant Wilson coefficients. Secondly, we perform frequentist fits to $R_K$ and $R_{K^{\ast }}$. The SM disagrees with these measurements at $3.7\sigma$ significance. We find excellent fits in scenarios with combinations of ${\mathcal{O}}_{9(10)}^{\ell }=\bar{s}{\gamma }^{\mu }{b}_L\ell {\gamma }_{\mu }({\gamma }_5)\ell$ operators, with pulls relative to the Standard Model in the region of $4\sigma$. An important conclusion of our analysis is that a lepton-specific contribution to ${\mathcal{O}}_{10}$ is essential to understand the data. Under the hypothesis that new-physics couples selectively to the muons, we also present fits to other $b\to s\mu \mu$ data with a conservative error assessment, and comment on more general scenarios. Finally, we discuss new lepton universality ratios that, if new physics is the origin of the observed discrepancy, should contribute to the statistically significant discovery of new physics in the near future.

    hep-phhep-exPRD(2017)·282 citations
20. 20*

    On Flavourful Easter eggs for New Physics hunger and Lepton Flavour Universality violation

    Marco Ciuchini🇮🇹 · Antonio M. Coutinho🇮🇹 · Marco Fedele🇮🇹 · Enrico Franco🇮🇹 · Ayan Paul🇮🇹 · Luca Silvestrini🇮🇹 · Mauro Valli🇮🇹

    Within the standard approach of effective field theory of weak interactions for $\Delta B=1$ transitions, we look for possibly unexpected subtle New Physics effects, here dubbed "flavourful Easter eggs". We perform a Bayesian global fit using the publicly available HEPfit package, taking into account state-of-the-art experimental information concerning these processes, including the suggestive measurements from LHCb of $R_K$ and $R_{K^{\ast }}$, the latter available only very recently. We parametrize New Physics contributions to $b\to s$ transitions in terms of shifts of Wilson coefficients of the electromagnetic dipole and semi-leptonic operators, assuming CP-conserving effects, but allowing in general for violation of lepton flavour universality. We show how optimistic/conservative hadronic estimates can impact quantitatively the size of New Physics extracted from the fit. With a conservative approach to hadronic uncertainties we find nonzero New Physics contributions to Wilson coefficients at the level of $\sim 3\sigma$, depending on the model chosen. Furthermore, given the interplay between hadronic contributions and New Physics effects in the leptonic vector current, a scenario with nonstandard leptonic axial currents is comparable to the more widely advocated one with New Physics in the leptonic vector current.

    hep-phastro-ph.HEhep-exEPJC(2017)·272 citations
21. 21*

    Generalized Fragmentation Functions for Fractal Jet Observables

    Benjamin T. Elder🇺🇸 · Massimiliano Procura🇨🇭 · Jesse Thaler🇺🇸 · Wouter J. Waalewijn🇳🇱 · Kevin Zhou🇺🇸

    We introduce a broad class of fractal jet observables that recursively probe the collective properties of hadrons produced in jet fragmentation. To describe these collinear-unsafe observables, we generalize the formalism of fragmentation functions, which are important objects in QCD for calculating cross sections involving identified final-state hadrons. Fragmentation functions are fundamentally nonperturbative, but have a calculable renormalization group evolution. Unlike ordinary fragmentation functions, generalized fragmentation functions exhibit nonlinear evolution, since fractal observables involve correlated subsets of hadrons within a jet. Some special cases of generalized fragmentation functions are reviewed, including jet charge and track functions. We then consider fractal jet observables that are based on hierarchical clustering trees, where the nonlinear evolution equations also exhibit tree-like structure at leading order. We develop a numeric code for performing this evolution and study its phenomenological implications. As an application, we present examples of fractal jet observables that are useful in discriminating quark jets from gluon jets.

    hep-phhep-exJHEP(2017)·33 citations
22. 22*

    The spin-dependent quark beam function at NNLO

    Radja Boughezal🇺🇸 · Frank Petriello🇺🇸 · Ulrich Schubert🇺🇸 · Hongxi Xing🇺🇸

    We calculate the beam function for longitudinally-polarized quarks through next-to-next-to-leading order (NNLO) in QCD perturbation theory. This is the last missing ingredient needed to apply the factorization theorem for the $N$-jettiness event-shape variable in polarized collisions through the NNLO level. We present all technical details of our derivation. As a by-product of our calculation we provide the first independent check of the previously-obtained unpolarized quark beam function. We anticipate that our result will have phenomenological applications in describing data from polarized collisions.

    hep-phnucl-thPRD(2017)·22 citations
23. 23*

    Maximal cuts and differential equations for Feynman integrals. An application to the three-loop massive banana graph

    Amedeo Primo🇮🇹 · Lorenzo Tancredi🇩🇪

    We consider the calculation of the master integrals of the three-loop massive banana graph. In the case of equal internal masses, the graph is reduced to three master integrals which satisfy an irreducible system of three coupled linear differential equations. The solution of the system requires finding a $3\times 3$ matrix of homogeneous solutions. We show how the maximal cut can be used to determine all entries of this matrix in terms of products of elliptic integrals of first and second kind of suitable arguments. All independent solutions are found by performing the integration which defines the maximal cut on different contours. Once the homogeneous solution is known, the inhomogeneous solution can be obtained by use of Euler's variation of constants.

    hep-phhep-thNPB(2017)·164 citations
24. 24*

    Holographic self-tuning of the cosmological constant

    Christos Charmousis🇫🇷 · Elias Kiritsis🇫🇷 · Francesco Nitti🇫🇷

    We propose a brane-world setup based on gauge/gravity duality in which the four-dimensional cosmological constant is set to zero by a dynamical self-adjustment mechanism. The bulk contains Einstein gravity and a scalar field. We study holographic RG flow solutions, with the standard model brane separating an infinite volume UV region and an IR region of finite volume. For generic values of the brane vacuum energy, regular solutions exist such that the four-dimensional brane is flat. Its position in the bulk is determined dynamically by the junction conditions. Analysis of linear fluctuations shows that a regime of 4-dimensional gravity is possible at large distances, due to the presence of an induced gravity term. The graviton acquires an effective mass, and a five-dimensional regime may exist at large and/or small scales. We show that, for a broad choice of potentials, flat-brane solutions are manifestly stable and free of ghosts. We compute the scalar contribution to the force between brane-localized sources and show that, in certain models, the vDVZ discontinuity is absent and the effective interaction at short distances is mediated by two transverse graviton helicities.

    ↳ hep-thgr-qchep-phJHEP(2017)·32 citations
25. 25*

    Constraining Relativistic Generalizations of Modified Newtonian Dynamics with Gravitational Waves

    Paul M. Chesler🇺🇸 · Abraham Loeb🇺🇸

    In the weak-field limit of General Relativity, gravitational waves obey linear equations and propagate at the speed of light. These properties of General Relativity are supported by the observation of ultra high energy cosmic rays as well as by LIGO's recent detection of gravitation waves. We argue that two existing relativistic generalizations of Modified Newtonian Dynamics, namely Generalized Einstein-Aether theory and BIMOND, display fatal inconsistencies with these observations.

    ↳ astro-ph.HEgr-qchep-phhep-thPRL(2017)·35 citations
26. 26*

    Jet modifications in event-by-event hydrodynamically evolving media

    Jacquelyn Noronha-Hostler🇺🇸

    The nearly perfect fluid-like nature of the Quark Gluon Plasma may be understood through two key experimental signatures: collective flow and jet suppression. Event-by-event relativistic viscous hydrodynamics (with an extremely small shear viscosity to entropy density ratio) has been very successful at describing collective flow observables for the last 7 years. More recently, the effects of event-by-event fluctuations have been studied in the context of high $p_T$ particles that lose energy as they pass through the dense Quark Gluon Plasma liquid. In this summary of the corresponding plenary talk at Quark Matter 2017, the recent developments on the effects of event-by-event fluctuations on jet suppression are summarized.

    ↳ nucl-thhep-phnucl-exNPA(2017)·0 citations
27. 27*

    High statistics study of in-medium S- and P-wave quarkonium states in lattice Non-relativistic QCD

    Seyong Kim🇰🇷 · Peter Petreczky🇺🇸 · Alexander Rothkopf🇩🇪

    Many measurements of quarkonium suppression at the LHC, e.g. the nuclear modification factor $R_{AA}$ of $J/\Psi$, are well described by a multitude of different models. Thus pinpointing the underlying physics aspects is difficult and guidance based on first principles is needed. Here we present the current status of our ongoing high precision study of in-medium spectral properties of both bottomonium and charmonium based on NRQCD on the lattice. This effective field theory allows us to capture the physics of quarkonium without modeling assumptions in a thermal QCD medium. In our study a first principles and realistic description of the QCD medium is provided by state-of-the-art lattices of the HotQCD collaboration at almost physical pion mass. Our updated results corroborate a picture of sequential modification of states with respect to their vacuum binding energy. Using a novel low-gain variant of the Bayesian BR method for reconstructing spectral functions we find that remnant features of the Upsilon may survive up to $T\sim 400$MeV, while the ${\chi }_b$ signal disappears around $T\sim 270$MeV. The $c\bar{c}$ analysis hints at melting of ${\chi }_c$ below $T\sim 190$MeV while some $J/\Psi$ remnant feature might survive up to $T\sim 245$MeV. An improved understanding of the numerical artifacts in the Bayesian approach and the availability of increased statistics have made possible a first quantitative study of the in-medium ground state masses, which tend to lower values as $T$ increases, consistent with lattice potential based studies.

    ↳ hep-lathep-phnucl-thNPA(2017)·2 citations
28. 28*

    Initial conditions for hydrodynamics from kinetic theory equilibration

    Aleksi Kurkela🇨🇭 · Aleksas Mazeliauskas🇺🇸 · Jean-François Paquet🇺🇸 · Sören Schlichting🇺🇸 · Derek Teaney🇺🇸

    We use effective kinetic theory to study the pre-equilibrium dynamics in heavy-ion collisions. We describe the evolution of linearized energy perturbations on top of out-of-equilibrium background to the energy-momentum tensor at a time when hydrodynamics becomes applicable. We apply this description to IP-Glasma initial conditions and find an overall smooth transition to hydrodynamics. In a phenomenologically favorable range of $\eta /s$ values, early time dynamics can be accurately described in terms of a few functions of a scaled time variable $\tau T/(\eta /s)$. Our framework can be readily applied to other initial state models to provide the pre-equilibrium dynamics of the energy momentum tensor.

    ↳ nucl-thhep-phNPA(2017)·5 citations
29. 29*

    Constraints on Axion-Like Particles from Non-Observation of Spectral Modulations for X-ray Point Sources

    Joseph P. Conlon🇬🇧 · Francesca Day🇬🇧 · Nicholas Jennings🇬🇧 · Sven Krippendorf🇬🇧 · Markus Rummel🇨🇦

    We extend previous searches for X-ray spectral modulations induced by ALP-photon conversion to a variety of new sources, all consisting of quasars or AGNs located in or behind galaxy clusters. We consider a total of seven new sources, with data drawn from the Chandra archive. In all cases the spectrum is well fit by an absorbed power-law with no evidence for spectral modulations, allowing constraints to be placed on the ALP-photon coupling parameter $g_{a\gamma \gamma }$. Two sources are particularly good: the Seyfert galaxy 2E3140 in A1795 and the AGN NGC3862 within the cluster A1367, leading to 95\% bounds for light ALPs ($m_a\lesssim 10^{-12}\mathrm{eV}$) of $g_{a\gamma \gamma }\lesssim 1.5\times 10^{-12}{\mathrm{GeV}}^{-1}$ and $g_{a\gamma \gamma }\lesssim 2.4\times 10^{-12}{\mathrm{GeV}}^{-1}$ respectively.

    ↳ astro-ph.HEhep-phJCAP(2017)·81 citations
30. 30*

    Asymptotically Safe Non-Minimal Inflation

    Alessandro Tronconi🇮🇹

    We study the constraints imposed by the requirement of Asymptotic Safety on a class of inflationary models with an inflaton field non-minimally coupled to the Ricci scalar. The critical surface in the space of theories is determined by the improved renormalization group flow which takes into account quantum corrections beyond the one loop approximation. The combination of constraints deriving from Planck observations and those from theory puts severe bounds on the values of the parameters of the model and predicts a quite large tensor to scalar ratio. We finally comment on the dependence of the results on the definition of the infrared energy scale which parametrises the running on the critical surface.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2017)·16 citations
31. 31*

    Real-Time dynamics and phase separation in a holographic first order phase transition

    Romuald A. Janik🇵🇱 · Jakub Jankowski🇵🇱 · Hesam Soltanpanahi🇮🇷

    We study the fully nonlinear time evolution of a holographic system possessing a first order phase transition. The initial state is chosen in the spinodal region of the phase diagram, and includes an inhomogeneous perturbation in one of the field theory directions. The final state of the time evolution shows a clear phase separation in the form of domain formation. The results indicate the existence of a very rich class of inhomogeneous black hole solutions.

    ↳ hep-thgr-qchep-phnucl-thPRL(2017)·60 citations
32. 32*

    Fatal youth of the Universe: black hole threat for the electroweak vacuum during preheating

    Dmitry Gorbunov🇷🇺 · Dmitry Levkov🇷🇺 · Alexander Panin🇷🇺

    Small evaporating black holes were proposed to be dangerous inducing fast decay of the electroweak false vacuum. We observe that the flat-spectrum matter perturbations growing at the post-inflationary matter dominated stage can produce such black holes in a tiny amount which may nevertheless be sufficient to destroy the vacuum in the visible part of the Universe via the induced process. If the decay probability in the vicinity of Planck-mass black holes was of order one as suggested in literature, the absence of such objects in the early Universe would put severe constraints on inflation and subsequent stages thus excluding many well-motivated models (e.g. the R^2-inflation) and supporting the need of new physics in the Higgs sector. We give a qualitative argument, however, that exponential suppression of the probability should persist in the limit of small black hole masses. This suppression relaxes our cosmological constraints, and, if sufficiently strong, may cancel them.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2017)·51 citations
33. 33*

    Cosmic rays, anti-helium, and an old navy spotlight

    Kfir Blum🇮🇱 · Kenny Chun Yu Ng🇮🇱 · Ryosuke Sato🇮🇱 · Masahiro Takimoto🇯🇵

    Cosmic-ray anti-deuterium and anti-helium have long been suggested as probes of dark matter, as their secondary astrophysical production was thought extremely scarce. But how does one actually predict the secondary flux? Anti-nuclei are dominantly produced in pp collisions, where laboratory cross section data is lacking. We make a new attempt at tackling this problem by appealing to a scaling law of nuclear coalescence with the physical volume of the hadronic emission region. The same volume is probed by Hanbury Brown-Twiss (HBT) two-particle correlations. We demonstrate the consistency of the scaling law with systems ranging from central and off-axis AA collisions to pA collisions, spanning 3 orders of magnitude in coalescence yield. Extending the volume scaling to the pp system, HBT data allows us to make a new estimate of coalescence, that we test against preliminary ALICE pp data. For anti-helium the resulting cross section is 1-2 orders of magnitude higher than earlier estimates. The astrophysical secondary flux of anti-helium could be within reach of a five-year exposure of AMS02.

    ↳ astro-ph.HEhep-phnucl-thPRD(2017)·116 citations
34. 34*

    $P$-wave $\pi \pi$ scattering and the $\rho$ resonance from lattice QCD

    Constantia Alexandrou🇨🇾 · Luka Leskovec🇺🇸 · Stefan Meinel🇺🇸 · John Negele🇺🇸 · Srijit Paul🇨🇾 · Marcus Petschlies🇩🇪 · Andrew Pochinsky🇺🇸 · Gumaro Rendon🇺🇸 · Sergey Syritsyn🇺🇸

    We calculate the parameters describing elastic $I=1$, $P$-wave $\pi \pi$ scattering using lattice QCD with $2+1$ flavors of clover fermions. Our calculation is performed with a pion mass of $m_{\pi }\approx 320\mathrm{MeV}$ and a lattice size of $L\approx 3.6$ fm. We construct the two-point correlation matrices with both quark-antiquark and two-hadron interpolating fields using a combination of smeared forward, sequential and stochastic propagators. The spectra in all relevant irreducible representations for total momenta $|\vec{P}|\le \sqrt{3}\frac{2\pi }{L}$ are extracted with two alternative methods: a variational analysis as well as multi-exponential matrix fits. We perform an analysis using Lüscher's formalism for the energies below the inelastic thresholds, and investigate several phase shift models, including possible nonresonant contributions. We find that our data are well described by the minimal Breit-Wigner form, with no statistically significant nonresonant component. In determining the $\rho$ resonance mass and coupling we compare two different approaches: fitting the individually extracted phase shifts versus fitting the $t$-matrix model directly to the energy spectrum. We find that both methods give consistent results, and at a pion mass of $a{m}_{\pi }=0.18295(36{)}_{stat}$ obtain $g_{\rho \pi \pi }=5.69(13{)}_{stat}(16{)}_{sys}$, $a{m}_{\rho }=0.4609(16{)}_{stat}(14{)}_{sys}$, and $a{m}_{\rho }/a{m}_N=0.7476(38{)}_{stat}(23{)}_{sys}$, where the first uncertainty is statistical and the second is the systematic uncertainty due to the choice of fit ranges.

    ↳ hep-lathep-phnucl-thPRD(2017)·133 citations
35. 35*

    A Fresh Approach to Forecasting in Astroparticle Physics and Dark Matter Searches

    Thomas D. P. Edwards🇳🇱 · Christoph Weniger🇳🇱

    We present a toolbox of new techniques and concepts for the efficient forecasting of experimental sensitivities. These are applicable to a large range of scenarios in (astro-)particle physics, and based on the Fisher information formalism. Fisher information provides an answer to the question what is the maximum extractable information from a given observation?. It is a common tool for the forecasting of experimental sensitivities in many branches of science, but rarely used in astroparticle physics or searches for particle dark matter. After briefly reviewing the Fisher information matrix of general Poisson likelihoods, we propose very compact expressions for estimating expected exclusion and discovery limits (equivalent counts method). We demonstrate by comparison with Monte Carlo results that they remain surprisingly accurate even deep in the Poisson regime. We show how correlated background systematics can be efficiently accounted for by a treatment based on Gaussian random fields. Finally, we introduce the novel concept of Fisher information flux. It can be thought of as a generalization of the commonly used signal-to-noise ratio, while accounting for the non-local properties and saturation effects of background and instrumental uncertainties. It is a powerful and flexible tool ready to be used as core concept for informed strategy development in astroparticle physics and searches for particle dark matter.

    ↳ astro-ph.IMastro-ph.COhep-phphysics.data-anJCAP(2018)·40 citations
36. 36*

    HEPData: a repository for high energy physics data

    Eamonn Maguire🇨🇭 · Lukas Heinrich🇺🇸 · Graeme Watt🇬🇧

    The Durham High Energy Physics Database (HEPData) has been built up over the past four decades as a unique open-access repository for scattering data from experimental particle physics papers. It comprises data points underlying several thousand publications. Over the last two years, the HEPData software has been completely rewritten using modern computing technologies as an overlay on the Invenio v3 digital library framework. The software is open source with the new site available at https://hepdata.net now replacing the previous site at http://hepdata.cedar.ac.uk. In this write-up, we describe the development of the new site and explain some of the advantages it offers over the previous platform.

    ↳ hep-excs.DLhep-phJ.Phys.Conf.Ser.(2017)·225 citations
37. 37*

    Superradiance in rotating stars and pulsar-timing constraints on dark photons

    Vitor Cardoso🇵🇹 · Paolo Pani🇮🇹 · Tien-Tien Yu🇨🇭

    In the presence of massive bosonic degrees of freedom, rotational superradiance can trigger an instability that spins down black holes. This leads to peculiar gravitational-wave signatures and distribution in the spin-mass plane, which in turn can impose stringent constraints on ultralight fields. Here, we demonstrate that there is an analogous spindown effect for conducting stars. We show that rotating stars amplify low frequency electromagnetic waves, and that this effect is largest when the time scale for conduction within the star is of the order of a light crossing time. This has interesting consequences for dark photons, as massive dark photons would cause stars to spin down due to superradiant instabilities. The time scale of the spindown depends on the mass of the dark photon, and on the rotation rate, compactness, and conductivity of the star. Existing measurements of the spindown rate of pulsars place direct constraints on models of dark sectors. Our analysis suggests that dark photons of mass $m_V\sim 10^{-12}$ eV are excluded by pulsar-timing observations. These constraints also exclude superradiant instabilities triggered by dark photons as an explanation for the spin limit of observed pulsars.

    ↳ gr-qcastro-ph.COhep-phphysics.class-phPRD(2017)·68 citations
38. 38*

    A Quantum Approach to Gravitational Waves

    Salah-Eddine Ennadifi🇲🇦

    In light of the Gravitational Waves observation and the discrete structure of spacetime at high scales M_QG, we investigate the behavior of Gravitational Waves and the spacetime deformation patterns in terms of gravitons and derive the effective results with respect to photons. Using the GW150914 data and related signals, we probe the underlying quantum scale M_QG 10_6 GeV.

    ↳ gr-qchep-ph0 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.