HEP Phenomenology·hep-ph

Mon·Nov 23, 2015Monday·November 23, 2015

17 papers—11 primary·6 cross-listed·reconstructed*

01*
Dynamic colour screening in diffractive deep inelastic scattering
Gunnar Ingelman🇸🇪 · Roman Pasechnik🇸🇪 · Dominik Werder🇸🇪
We present a novel Monte-Carlo implementation of dynamic colour screening via multiple exchanges of semi-soft gluons as a basic QCD mechanism to understand diffractive electron-proton scattering at the HERA collider. Based on the kinematics of individual events in the standard QCD description of deep inelastic scattering at the parton level, which at low $x$ is dominantly gluon-initiated, the probability is evaluated for additional exchanges of softer gluons resulting in an overall colour singlet exchange leading to a forward proton and a rapidity gap as the characteristic observables for diffractive scattering. The probability depends on the impact parameter of the soft exchanges and varies with the transverse size of the hard scattering subsystem and is therefore influenced by different QCD effects. We account for matrix elements and parton shower evolution either via conventional DGLAP $lo g Q^{2}$ -evolution with collinear factorisation or CCFM small- $x$ evolution with $k_{⊥}$ -factorisation and discuss the sensitivity to the gluon density distribution in the proton and the importance of large log\, $x$ -contributions. The overall result is that, with only two model parameters which have theoretically motivated values, a satisfactory description of the observed diffractive cross-section at HERA is obtained in a wide kinematical range.
hep-phPRD(2016)·7 citations
02*
The prompt atmospheric neutrino flux in the light of LHCb
Rhorry Gauld🇬🇧 · Juan Rojo🇬🇧 · Luca Rottoli🇬🇧 · Subir Sarkar🇬🇧 · Jim Talbert🇬🇧
The recent observation of very high energy cosmic neutrinos by IceCube heralds the beginning of neutrino astronomy. At these energies, the dominant background to the astrophysical signal is the flux of `prompt' neutrinos, arising from the decay of charmed mesons produced by cosmic ray collisions in the atmosphere. In this work we provide predictions for the prompt atmospheric neutrino flux in the framework of perturbative QCD, using state-of-the-art Monte Carlo event generators. Our calculation includes the constraints set by charm production measurements from the LHCb experiment at 7 TeV, and has been recently validated with the corresponding 13 TeV data. Our results for the prompt flux are a factor of about 2 below the previous benchmark calculation, in general agreement with two other recent estimates, and with an improved estimate of the uncertainty. This alleviates the existing tension between the theoretical prediction and IceCube limits, and suggests that a direct direction of the prompt flux is imminent.
hep-phastro-ph.HEhep-exJHEP(2016)·115 citations
03*
Axion Isocurvature and Magnetic Monopoles
Yasunori Nomura🇺🇸 · Surjeet Rajendran🇺🇸 · Fabio Sanches🇺🇸
We propose a simple mechanism to suppress axion isocurvature fluctuations using hidden sector magnetic monopoles. This allows for the Peccei-Quinn scale to be of order the unification scale consistently with high scale inflation.
hep-phastro-ph.COPRL(2016)·68 citations
04*
Non-Standard Interactions in propagation at the Deep Underground Neutrino Experiment
Pilar Coloma🇺🇸
We study the sensitivity of current and future long-baseline neutrino oscillation experiments to the effects of dimension six operators affecting neutrino propagation through Earth, commonly referred to as Non-Standard Interactions (NSI). All relevant parameters entering the oscillation probabilities (standard and non-standard) are considered at once, in order to take into account possible cancellations and degeneracies between them. We find that the Deep Underground Neutrino Experiment will significantly improve over current constraints for most NSI parameters. Most notably, it will be able to rule out the so-called LMA-dark solution, still compatible with current oscillation data, and will be sensitive to off-diagonal NSI parameters at the level of $ε \sim O (0.05 - 0.5)$ . We also identify two degeneracies among standard and non-standard parameters, which could be partially resolved by combining T2HK and DUNE data.
hep-phhep-exJHEP(2016)·143 citations
05*
Neutrino Anarchy and Renormalization Group Evolution
Vedran Brdar🇩🇪 · Matthias König🇩🇪 · Joachim Kopp (Johannes Gutenberg University Mainz)🇩🇪
The observed pattern of neutrino mixing angles is in good agreement with the hypothesis of neutrino anarchy, which posits that Nature has chosen the entries of the leptonic mixing matrix at random. In this paper we investigate how stable this conclusion is under renormalization group effects. Working in the simplest type-I seesaw model and two variants of the inverse seesaw model we study how the statistical distributions of the neutrino mixing parameters evolve between the Grand Unification scale and the electroweak scale. Especially in the inverse seesaw case we find significant distortions: mixing angles tend to be smaller after RG running, and the Dirac CP phase tends to be closer to zero. The p-value describing the compatibility between the observed mixing angles and the anarchy hypothesis increases by 10-20%. This illustrates that RG effects are highly relevant for quantitative studies of the anarchy scenario.
hep-phPRD(2016)·12 citations
06*
Type II Radiative Seesaw Model of Neutrino Mass with Dark Matter
Sean Fraser🇺🇸 · Corey Kownacki🇺🇸 · Ernest Ma🇺🇸 · Oleg Popov🇺🇸
We consider a model of neutrino mass with a scalar triplet $(ξ^{++}, ξ^{+}, ξ^{0})$ assigned lepton number $L = 0$ , so that the tree-level Yukawa coupling $ξ^{0} ν_{i} ν_{j}$ is not allowed. It is generated instead through the interaction of $ξ$ and $ν$ with dark matter and the soft breaking of $L$ to $(- 1)^{L}$ . We discuss the phenomenological implications of this model, including $ξ^{++}$ decay and the prognosis of discovering the dark sector at the Large Hadron Collider.
hep-phPRD(2016)·48 citations
07*
Constraining the Strength and CP Structure of Dark Production at the LHC: the Associated Top-Pair Channel
Matthew R. Buckley🇺🇸 · Dorival Goncalves🇬🇧
We consider the production of dark matter in association with a pair of top quarks, mediated by a scalar or pseudoscalar particle in a generic Simplified Model. We demonstrate that the difference of azimuthal angle between the two leptons $Δ ϕ_{l l}$ , in the dileptonic top decay mode, can directly probe the CP-properties of the mediator. We estimate the constraints to strength and CP-structure of dark matter production for these well-motivated Simplified Models from the LHC Run II.
hep-phPRD(2016)·51 citations
08*
Topological Susceptibility in Three-Flavor Quark Meson Model at Finite Temperature
Yin Jiang🇺🇸 · Tao Xia🇨🇳 · Pengfei Zhuang🇨🇳
We study $U_{A} (1)$ symmetry and its relation to chiral symmetry at finite temperature through the application of functional renormalization group to the $S U (3)$ quark meson model. Very different from the mass gap and mixing angel between $η$ and $η^{'}$ mesons which are defined at mean field level and behavior like the chiral condensates, the topological susceptibility includes a fluctuations induced part which becomes dominant at high temperature. As a result, the $U_{A} (1)$ symmetry is still considerably broken in the chiral symmetry restoration phase.
hep-phhep-thnucl-thPRD(2016)·25 citations
09*
Nonperturbative contribution to the strange-antistrange asymmetry of the nucleon sea
Alfredo Vega🇨🇱 · Ivan Schmidt🇨🇱 · Thomas Gutsche🇩🇪 · Valery E. Lyubovitskij🇩🇪
We give predictions for the nonperturbative (intrinsic) contribution to the $s (x) - s ˉ (x)$ asymmetry of the nucleon sea. For this purpose we use different light-front wave functions inspired by the AdS/QCD formalism, together with a model of the nucleon in terms of meson-baryon fluctuations. The holographic wave functions for an arbitrary number of constituents, recently derived by us, give results quite close to known parametrizations that appear in the literature.
hep-phnucl-thPRD(2016)·18 citations
10*
Physics Opportunities of a 100 TeV Proton-Proton Collider
Nima Arkani-Hamed🇺🇸 · Tao Han🇺🇸 · Michelangelo Mangano🇨🇭 · Lian-Tao Wang🇺🇸
The discovery of the Higgs boson at the LHC exposes some of the most profound mysteries fundamental physics has encountered in decades, opening the door to the next phase of experimental exploration. More than ever, this will necessitate new machines to push us deeper into the energy frontier. In this article, we discuss the physics motivation and present the physics potential of a proton-proton collider running at an energy significantly beyond that of the LHC and a luminosity comparable to that of the LHC. 100 TeV is used as a benchmark of the center of mass energy, with integrated luminosities from 3 inverse ab to 30 inverse ab.
hep-phPhys.Rept.(2016)·297 citations
11*
Gauge-invariant approach to quark dynamics
H. Sazdjian🇫🇷
The main aspects of a gauge-invariant approach to the description of quark dynamics in the nonperturbative regime of QCD are first reviewed. In particular, the role of the parallel transport operation in constructing gauge-invariant Green's functions is presented, and the relevance of Wilson loops for the representation of the interaction is emphasized. Recent developments, based on the use of polygonal lines for the parallel transport operation, are then presented. An integro-differential equation is obtained for the quark Green's function defined with a phase factor along a single, straight line segment. It is solved exactly and analytically in the case of two-dimensional QCD in the large $N_{c}$ limit. The solution displays the dynamical mass generation phenomenon for quarks, with an infinite number of branch-cut singularities that are stronger than simple poles.
hep-phFront.Phys.(Beijing)(2016)·0 citations
12*
Holographic model for heavy vector meson masses
Nelson R. F. Braga🇧🇷 · M. A. Martin Contreras🇨🇴 · Saulo Diles🇧🇷
The experimentally observed spectra of heavy vector meson radial excitations show a dependence on two different energy parameters. One is associated with the quark mass and the other with the binding energy levels of the quark anti-quark pair. The first is present in the large mass of the first state while the other corresponds to the small mass splittings between radial excitations. In this article we show how to reproduce such a behavior with reasonable precision using a holographic model. In the dual picture, the large energy scale shows up from a bulk mass and the small scale comes from the position of anti-de Sitter (AdS) space where field correlators are calculated. The model determines the masses of four observed S-wave states of charmonium and six S-wave states of bottomonium with , 6.1 % rms error. In consistency with the physical picture, the large energy parameter is flavor dependent, while the small parameter, associated with quark anti-quark interaction is the same for charmonium and bottomonium states.
↳ hep-thhep-phEPL(2016)·29 citations
13*
Separate Einstein-Eddington Spaces and the Cosmological Constant
Hemza Azri🇹🇷
Based on Eddington affine variational principle on a locally product manifold, we derive the separate Einstein space described by its Ricci tensor. The derived field equations split into two field equations of motion that describe two maximally symmetric spaces with two cosmological constants. We argue that the invariance of the bi-field equations under projections on the separate spaces, may render one of the cosmological constants to zero. We also formulate the model in the presence of a scalar field. The resulted separate Einstein-Eddington spaces maybe considered as two states that describe the universe before and after inflation. A possibly interesting affine action for a general perfect fluid is also proposed. It turns out that the condition which leads to zero cosmological constant in the vacuum case, eliminates here the effects of the gravitational mass density of the perfect fluid, and the dynamic of the universe in its final state is governed by only the inertial mass density of the fluid.
↳ gr-qchep-phhep-thAnnalen Phys.(2016)·10 citations
14*
Meson assisted dibaryons
Avraham Gal🇮🇱
We discuss a new type of L=0 positive-parity dibaryons, pion-B-B', where the dominant binding mechanism is provided by resonating p-wave pion-baryon interactions. Recent calculations of such pion assisted dibaryons are reviewed with special emphasis placed on the non-strange I(JP)=1(2+) N-Delta dibaryon D_{12}(2150) studied recently at JLab, and on the 0(3+) Delta-Delta dibaryon D_{03}(2380) discovered recently by the WASA-at-COSY Collaboration. We review recent searches by the HADES Collaboration at GSI and by the E15 and E27 Experiments at J-PARC for a strangeness S=-1 I(JP)=1/2(0-) K-pp dibaryon and perhaps also for a strange I(JP)=3/2(2+) N-Sigma(1385) pion assisted dibaryon Y_{3/2(2+)}(2270). Charm C=+1 dibaryons, predicted with these same I(JP) values, are also briefly reviewed.
↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2016)·35 citations
15*
An effective field theory during inflation II: stochastic dynamics and power spectrum suppression
D. Boyanovsky🇺🇸
We obtain the non-equilibrium effective action of an inflaton like scalar field --the system-- by tracing over sub Hubble degrees of freedom of "environmental" light scalar fields. The effective action is stochastic leading to effective Langevin equations of motion for the fluctuations of the inflaton-like field, with self-energy corrections and stochastic noise correlators that obey a de Sitter space-time analog of a fluctuation dissipation relation. We solve the Langevin equation implementing a dynamical renormalization group resummation of the leading secular terms and obtain the corrections to the power spectrum of super Hubble fluctuations of the inflaton field, $P (k; η) = P_{0} (k) e^{- γ (k; η)}$ where $P_{0} (k)$ is the nearly scale invariant power spectrum in absence of coupling. $γ (k; η) > 0$ describes the suppression of the power spectrum, it features Sudakov-type double logarithms and entails violations of scale invariance. We also obtain the effective action for the case of a heavy scalar field of mass $M ≫ H$ , this case yields a local "Fermi" limit with a very weak self-interaction of the inflaton-like field and dissipative terms that are suppressed by powers of $H / M$ . We conjecture on the possibility that the large scale anomalies in the CMB may originate in dissipative processes from inflaton coupling to sub-Hubble degrees of freedom.
↳ astro-ph.COgr-qchep-phhep-thPRD(2016)·95 citations
16*
Chirped-Frequency Excitation of Gravitationally Bound Ultracold Neutrons
Giovanni Manfredi🇫🇷 · Omar Morandi🇫🇷 · Lazar Friedland🇮🇱 · Tobias Jenke🇦🇹 · Hartmut Abele🇦🇹
Ultracold neutrons confined in the Earth's gravitational field display quantized energy levels that have been observed for over a decade. In recent resonance spectroscopy experiments [T. Jenke et al., Nature Phys. 7, 468 (2011)], the transition between two such gravitational quantum states was driven by the mechanical oscillation of the plates that confine the neutrons. Here we show that, by applying a sinusoidal modulation with slowly varying frequency (chirp), the neutrons can be brought to higher excited states by climbing the energy levels one by one. The proposed experiment should make it possible to observe the quantum-classical transition that occurs at high neutron energies. Furthermore, it provides a technique to realize superpositions of gravitational quantum states, to be used for precision tests of gravity at short distances.
↳ quant-phgr-qchep-phPRD(2017)·10 citations
17*
One-Loop Soft Theorems via Dual Superconformal Symmetry
Andreas Brandhuber🇬🇧 · Edward Hughes🇬🇧 · Bill Spence🇬🇧 · Gabriele Travaglini🇬🇧
We study soft theorems at one loop in planar N=4 super Yang-Mills theory through finite order in the infrared regulator and to subleading order in the soft parameter {\delta}. In particular, we derive a universal constraint from dual superconformal symmetry, which we use to bootstrap subleading log {\delta} behaviour. Moreover, we determine the complete infrared-finite subleading soft contribution of n-point MHV amplitudes using momentum twistors. Finally, we compute the subleading log {\delta} behaviour of one-loop NMHV ratio functions at six and seven points, finding that universality holds within but not between helicity sectors.
↳ hep-thhep-phJHEP(2016)·17 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.