Fri·Feb 7, 2020Friday·February 7, 2020

1. 01*

   CP Violation in Same-sign Dilepton Production at the LHC

   Fatemeh Najafi🇨🇦 · Jacky Kumar🇨🇦 · David London🇨🇦 · Richard MacKenzie🇨🇦

   If the neutrino is a Majorana particle, low-energy lepton-number-violating (LNV) processes, such as neutrinoless double-beta ($0\nu \beta \beta$) decay, are possible. It may also be possible to observe high-energy $0\nu \beta \beta$-like LNV processes at the LHC. These are distinguished by the presence of same-sign dileptons in the final state (e.g., $\bar{u}d\to t\bar{b}{e}^{-}{\mu }^{-}$). In this paper, we show that CP-violating triple products (TPs) may be present in the process, and may be measurable at the LHC. If a nonzero TP were observed, it would give us much information about the underlying new physics (NP). We would know that there are (at least) two interfering NP amplitudes, with different weak phases and different Lorentz structures. And if we had some knowledge of the NP, e.g., by direct production of NP particles, we could get information about the magnitudes and relative phases of its couplings.

   hep-phhep-exPRD(2020)·1 citation
2. 02*

   Inert doublet as multicomponent dark matter

   Amalia Betancur🇨🇴 · Guillermo Palacio🇨🇴 · Andrés Rivera🇨🇴

   In this work, we study multicomponent dark sectors comprised of a fermionic and a scalar dark matter candidate. In the scalar sector, we mostly focus on the Inert Doublet Model while in the fermionic sector we study three different models. For all of them, we investigate the impact that dark matter conversion and regular WIMP dark matter annihilating processes have on the relic abundance. We mostly recover the region between the electroweak scale and $\sim$ 550 GeV for the scalar dark matter mass, which is usually excluded in the Inert Doublet Model. We also consider current constraints from both direct detection and indirect detection experiments and include future prospects to probe the models. Additionally, we investigate constraints from collider searches on the fermionic dark matter candidates.

   hep-phphysics.comp-phNPB(2021)·20 citations
3. 03*

   JIMWLK Evolution, Lindblad Equation and Quantum-Classical Correspondence

   Ming Li🇺🇸 · Alex Kovner🇺🇸

   In the Color Glass Condensate(CGC) effective theory, the physics of valence gluons with large longitudinal momentum is reflected in the distribution of color charges in the transverse plane. Averaging over the valence degrees of freedom is effected by integrating over classical color charges with some quasi probability weight functional $W[\mathbf{j}]$ whose evolution with rapidity is governed by the JIMWLK equation. In this paper, we reformulate this setup in terms of effective quantum field theory on valence Hilbert space governed by the reduced density matrix $\hat{\rho }$ for hard gluons, which is obtained after properly integrating out the soft gluon "environment". We show that the evolution of this density matrix with rapidity in the dense and dilute limits has the form of Lindblad equation. The quasi probability distribution (weight) functional $W$ is directly related to the reduced density matrix $\hat{\rho }$ through the generalization of the Wigner-Weyl quantum-classical correspondence, which reformulates quantum dynamics on Hilbert space in terms of classical dynamics on the phase space. In the present case the phase space is non Abelian and is spanned by the components of transverse color charge density $\mathbf{j}$. The same correspondence maps the Lindblad equation for $\hat{\rho }$ into the JIMWLK evolution equation for $W$ .

   hep-phhep-thnucl-thJHEP(2020)·18 citations
4. 04*

   Deriving canonical differential equations for Feynman integrals from a single uniform weight integral

   Christoph Dlapa🇩🇪 · Johannes Henn🇩🇪 · Kai Yan🇩🇪

   Differential equations are a powerful tool for evaluating Feynman integrals. Their solution is straightforward if a transformation to a canonical form is found. In this paper, we present an algorithm for finding such a transformation. This novel technique is based on a method due to Hoschele et al. and relies only on the knowledge of a single integral of uniform transcendental weight. As a corollary, the algorithm can also be used to test the uniform transcendentality of a given integral. We discuss the application to several cutting-edge examples, including non-planar four-loop HQET and non-planar two-loop five-point integrals. A Mathematica implementation of our algorithm is made available together with this paper.

   hep-phhep-thmath-phmath.MPJHEP(2020)·114 citations
5. 05*

   Neutrino and $Z^{\prime }$ phenomenology in an anomaly-free $\mathbf{U}(1)$ extension: role of higher-dimensional operators

   Debajyoti Choudhury🇮🇳 · Kuldeep Deka🇮🇳 · Tanumoy Mandal🇸🇪 · Soumya Sadhukhan🇮🇳

   We consider an anomaly-free $\mathrm{U}(1)$ extension of the Standard Model with three right-handed neutrinos (RHNs) and two complex scalars, wherein the charge assignments preclude all tree-level mass terms for the neutrinos. Considering this setup, in turn, to be only a low-energy effective theory, we introduce higher-dimensional terms {\em a la} Froggatt-Nielsen to naturally generate tiny neutrino masses. One of the RHNs turns out to be very light, thereby constituting the main decay mode for the $Z^{\prime }$ and hence relaxing the LHC dilepton resonance search constraints. This very RHN has a lifetime comparable to or bigger than the age of the Universe, and, hence, could account for a non-negligible fraction of the dark matter.

   hep-phJHEP(2020)·26 citations
6. 06*

   How does the $S_{11}$ $N^{\ast }(890)$ state emerge from a naive $K$ matrix fit?

   Yao Ma🇨🇳 · Wen-Qi Niu🇨🇳 · Yu-Fei Wang🇨🇳 · Han-Qing Zheng🇨🇳

   We give a pedagogical analysis on $K$ matrix models describing the $\pi N$ scattering amplitude, in $S_{11}$ channel at low energies. We show how the correct use of analyticity in the $s$ channel and crossing symmetry in $t$ and $u$ channels leads to a much improved analytic behavior in the negative $s$ region, in agreement with the prediction from chiral perturbation amplitudes in its validity region. The analysis leads again to the conclusion that a genuine $N^{\ast }(890)$ resonance exists.

   hep-phnucl-thCommun.Theor.Phys.(2020)·9 citations
7. 07*

   Relaxing the Higgs mass and its vacuum energy by living at the top of the potential

   Alessandro Strumia🇮🇹 · Daniele Teresi🇮🇹

   We consider an ultra-light scalar coupled to the Higgs in the presence of heavier new physics. In the electroweak broken phase the Higgs gives a tree-level contribution to the light-scalar potential, while new physics contributes at loop level. Thereby, the theory has a cosmologically meta-stable phase where the light scalar is around the top of its potential, and the Higgs is a loop factor lighter than new physics. Such regions with precarious naturalness are anthropically and environmentally selected, as regions with heavier Higgs crunch quickly. We expect observable effects of rolling in the dark-energy equation of state. Furthermore, vacuum energies up to the weak scale can be canceled down to anthropically small values.

   hep-phastro-ph.COhep-thPRD(2020)·32 citations
8. 08*

   A Review of the Exceptional Supersymmetric Standard Model

   S. F. King🇬🇧 · S. Moretti🇬🇧 · R. Nevzorov🇷🇺

   Local supersymmetry (SUSY) provides an attractive framework for the incorporation of gravity and unification of gauge interactions within Grand Unified Theories (GUTs). Its breakdown can lead to a variety of models with softly broken SUSY at low energies. In this review article we focus on the SUSY extension of the Standard Model (SM) with an extra U(1)_{N} gauge symmetry originating from a string-inspired E_6 grand unified gauge group. Only in this U(1) extension of the minimal supersymmetric standard model (MSSM) inspired by E_6 GUTs the right-handed neutrinos can be superheavy providing a mechanism for the generation of the lepton and baryon asymmetry of the Universe. The particle content of this exceptional supersymmetric standard model (E_6SSM) includes three 27 representations of the E_6 group, to ensure anomaly cancellation, plus a pair of SU(2)_W doublets as required for gauge coupling unification. Thus E_6SSM involves extra exotic matter beyond the MSSM. We consider symmetries that permit to suppress non-diagonal flavour transitions and rapid proton decay, as well as gauge coupling unification, the breakdown of the gauge symmetry and the spectrum of Higgs bosons in this model. The possible Large Hadron Collider (LHC) signatures caused by the presence of exotic states are also discussed.

   hep-phhep-thSymmetry(2020)·22 citations
9. 09*

   $B\to \rho$ Decay Form Factors from Covariant Confined Quark Model

   Aidos Issadykov🇷🇺

   We evaluate $B\to \rho$ transition form factors in the full kinematical region within the covariant confined quark model. We compare the obtained results with the results from light-cone sum rules. The calculated form factors can be used to calculate the $B^{+}\to {\rho }^{+}{\mu }^{+}{\mu }^{-}$ rare decay branching ratio.

   hep-phAIP Conf.Proc.(2019)·4 citations
10. 10*

    Self-Interacting Dark Matter and the Origin of Ultra-Diffuse Galaxies NGC1052-DF2 and -DF4

    Daneng Yang🇨🇳 · Hai-Bo Yu🇺🇸 · Haipeng An🇨🇳

    Observations of ultra-diffuse galaxies NGC 1052-DF2 and -DF4 show they may contain little dark matter, challenging our understanding of galaxy formation. Using controlled N-body simulations, we explore the possibility that their properties can be reproduced through tidal stripping from the elliptical galaxy NGC 1052, in both cold dark matter (CDM) and self-interacting dark matter (SIDM) scenarios. To explain the dark matter deficiency, we find that a CDM halo must have a very low concentration so that it can lose sufficient inner mass in the tidal field. In contrast, SIDM favors a higher and more reasonable concentration as core formation enhances tidal mass loss. Final stellar distributions in our SIDM benchmarks are more diffuse than the CDM one, and hence the former are in better agreement with the data. We further show that a cored CDM halo model modified by strong baryonic feedback is unlikely to reproduce the observations. Our results indicate that SIDM is more favorable for the formation of dark-matter-deficient galaxies.

    ↳ astro-ph.GAhep-phPRL(2020)·51 citations
11. 11*

    Joseph Polchinski: A Biographical Memoir

    Raphael Bousso🇺🇸 · Fernando Quevedo🇬🇧 · Steven Weinberg🇺🇸

    Joseph Polchinski (1954-2018), one of the the leading theoretical physicists of the past 50 years, was an exceptionally broad and deep thinker. He made fundamental contributions to quantum field theory, advancing the role of the renormalization group, and to cosmology, addressing the cosmological constant problem. Polchinski's work on D-branes revolutionized string theory and led to the discovery of a nonperturbative quantum theory of gravity. His recent, incisive reformulation of the black hole information paradox presents us with a profound challenge. Joe was deeply devoted to his family, a beloved colleague and advisor, an excellent writer, and an accomplished athlete.

    ↳ physics.hist-phgr-qchep-phhep-th+12 citations
12. 12*

    Initial conditions for plateau inflation: a case study

    Tommi Tenkanen🇺🇸 · Eemeli Tomberg🇪🇪

    We study initial conditions for inflation in scenarios where the inflaton potential has a plateau shape. Such models are those most favored by Planck data and can be obtained in a large number of model classes. As a representative example, we consider Higgs inflation with and without an $R^2$ term in the context of Palatini gravity. We show that inflation with a large number of e-folds generically occurs in a large part of the parameter space without any fine-tuning of parameters even when the scale of inflation and the inflaton field value during inflation are much smaller than the Planck scale. We discuss consequences for detection of primordial gravitational waves and spectral tilt of curvature perturbations, as well as the recently proposed "Trans-Planckian Censorship" conjecture.

    ↳ astro-ph.COgr-qchep-phJCAP(2020)·49 citations
13. 13*

    Towards a Swampland Global Symmetry Conjecture using Weak Gravity

    Tristan Daus🇩🇪 · Arthur Hebecker🇩🇪 · Sascha Leonhardt🇩🇪 · John March-Russell🇬🇧

    It is widely believed and in part established that exact global symmetries are inconsistent with quantum gravity. One then expects that approximate global symmetries can be quantitatively constrained by quantum gravity or swampland arguments. We provide such a bound for an important class of global symmetries: Those arising from a gauged $U(1)$ with the vector made massive via Higgsing with an axion. The latter necessarily couples to instantons, and their action can be constrained, using both the electric and magnetic version of the axionic weak gravity conjecture, in terms of the cutoff of the theory. As a result, instanton-induced symmetry breaking operators with a suppression factor not smaller than $\exp (-M_{\mathrm{P}}^2/{\Lambda }^2)$ are present, where $\Lambda$ is a cutoff of the 4d effective theory. We provide a general argument and clarify the meaning of $\Lambda$. Simple 4d and 5d models are presented to illustrate this, and we recall that this is the standard way in which things work out in string compactifications with brane instantons. The relation of our constraint to bounds that can be derived from wormholes or gravitational instantons and to those motivated by black-hole effects at finite temperature are discussed, and we present a generalization of the Giddings-Strominger wormhole solution to the case of a gauge-derived $U(1)$ global symmetry. Finally, we discuss potential loopholes to our arguments.

    ↳ hep-thhep-phNPB(2020)·54 citations
14. 14*

    Universality in the classical limit of massless gravitational scattering

    Zvi Bern🇺🇸 · Harald Ita🇩🇪 · Julio Parra-Martinez🇺🇸 · Michael S. Ruf🇩🇪

    We demonstrate the universality of the gravitational classical deflection angle of massless particles through O(G^3) by studying the high-energy limit of full two-loop four-graviton scattering amplitudes in pure Einstein gravity as well as N >= 4 supergravity. As a by-product, our first-principles calculation provides a direct confirmation of the massless deflection angle in Einstein gravity proposed long ago by Amati, Ciafaloni and Veneziano, and is inconsistent with a recently proposed alternative.

    ↳ hep-thgr-qchep-phPRL(2020)·143 citations
15. 15*

    Intelligent Arxiv: Sort daily papers by learning users topics preference

    Ezequiel Alvarez (ICAS)🇦🇷 · Federico Lamagna (CAB)🇦🇷 · Cesar Miquel (Easytech)🇦🇷 · Manuel Szewc (ICAS)🇦🇷

    Current daily paper releases are becoming increasingly large and areas of research are growing in diversity. This makes it harder for scientists to keep up to date with current state of the art and identify relevant work within their lines of interest. The goal of this article is to address this problem using Machine Learning techniques. We model a scientific paper to be built as a combination of different scientific knowledge from diverse topics into a new problem. In light of this, we implement the unsupervised Machine Learning technique of Latent Dirichlet Allocation (LDA) on the corpus of papers in a given field to: i) define and extract underlying topics in the corpus; ii) get the topics weight vector for each paper in the corpus; and iii) get the topics weight vector for new papers. By registering papers preferred by a user, we build a user vector of weights using the information of the vectors of the selected papers. Hence, by performing an inner product between the user vector and each paper in the daily Arxiv release, we can sort the papers according to the user preference on the underlying topics. We have created the website IArxiv.org where users can read sorted daily Arxiv releases (and more) while the algorithm learns each users preference, yielding a more accurate sorting every day. Current IArxiv.org version runs on Arxiv categories astro-ph, gr-qc, hep-ph and hep-th and we plan to extend to others. We propose several new useful and relevant implementations to be additionally developed as well as new Machine Learning techniques beyond LDA to further improve the accuracy of this new tool.

    ↳ cs.LGastro-ph.HEgr-qchep-ph+20 citations
16. 16*

    Melting holographic mesons by cooling a magnetized quark gluon plasma

    Daniel Ávila🇲🇽 · Leonardo Patiño🇲🇽

    We extend our analysis of holographic meson dissociation in the presence of an intense magnetic field. In addition to the previously known critical temperature above which the mesons melt, we found that for certain magnetic field intensities there exists a second lower critical temperature, below which stable mesons cease to exist. While we showed before that there is a range of high temperatures for which mesons can be melted by changing the magnetic field intensity, here we show that, as a consequence of the second critical point, there is also a range of low temperatures for which this phenomenom, which we term Magnetic Meson Melting (MMM), can be triggered. Additionaly, we also show that the magnetic field decreases the mass gap of the meson spectrum along with their masses. We are able to observe this by constructing a configuration that makes it possible to apply gauge/gravity methods to study fundamental degrees of freedom in a quark-gluon plasma subject to a magnetic field as intense as that expected in high energy collisions. This is achieved by the confection of a ten-dimensional background that is dual to the magnetized plasma and nonetheless permits the embedding of D7-branes in it. The main difference with previous approaches, which in consequence gives the novel results, is that the magnetic field retroacts in the geometry itself, as opposed to be confined to the world volume of the probe D7-branes.

    ↳ hep-thgr-qchep-phJHEP(2020)·13 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.