Thu·Jun 20, 2019Thursday·June 20, 2019

1. 01*

   Naturalness versus stringy naturalness (with implications for collider and dark matter searches)

   Howard Baer🇺🇸 · Vernon Barger🇺🇸 · Shadman Salam🇺🇸

   The notion of stringy naturalness-- that an observable O_2 is more natural than O_1 if more (phenomenologically acceptable) vacua solutions lead to O_2 rather than O_1-- is examined within the context of the Standard Model (SM) and various SUSY extensions: CMSSM/mSUGRA, high-scale SUSY and radiatively-driven natural SUSY (RNS). Rather general arguments from string theory suggest a (possibly mild) statistical draw towards vacua with large soft SUSY breaking terms. These vacua must be tempered by an anthropic veto of non-standard vacua or vacua with too large a value of the weak scale m(weak). We argue that the SM, the CMSSM and the various high-scale SUSY models are all expected to be relatively rare occurances within the string theory landscape of vacua. In contrast, models with TeV-scale soft terms but with m(weak)~100 GeV and consequent light higgsinos (SUSY with radiatively-driven naturalness) should be much more common on the landscape. These latter models have a statistical preference for m_h~ 125 GeV and strongly interacting sparticles beyond current LHC reach. Thus, while conventional naturalness favors sparticles close to the weak scale, stringy naturalness favors sparticles so heavy that electroweak symmetry is barely broken and one is living dangerously close to vacua with charge-or-color breaking minima, no electroweak breaking or pocket universe weak scale values too far from our measured value. Expectations for how landscape SUSY would manifest itself at collider and dark matter search experiments are then modified compared to usual notions.

   hep-phPRResearch(2019)·31 citations
2. 02*

   QCD evolution of the orbital angular momentum of quarks and gluons: Genuine twist-three part

   Yoshitaka Hatta🇺🇸 · Xiaojun Yao🇺🇸

   We present the numerical solution of the one-loop QCD evolution equation for the genuine twist-three part of the orbital angular momentum (OAM) distributions of quarks and gluons inside a longitudinally polarized nucleon. This is based on the observation that the evolution is identical to that of the Efremov-Teryaev-Qiu-Sterman function for transverse single spin asymmetry. Together with the known evolution of the Wandzura-Wilczek part, the one-loop evolution of OAM distributions is now practically under control. We also study, for the first time, the scale dependence of the potential angular momentum defined as the difference between the Ji and Jaffe-Manohar definitions of OAM.

   hep-phnucl-thPLB(2019)·14 citations
3. 03*

   CP Violation in ${\bar{B}}^0\to D^{\ast +}{\ell }^{-}{\bar{\nu }}_{\ell }$

   David London🇨🇦

   At present, there are discrepancies with the predictions of the standard model in ${\bar{B}}^0\to D^{\ast +}{\ell }^{-}{\bar{\nu }}_{\ell }$ decays, hinting at the presence of new physics (NP) in $b\to c{\tau }^{-}\bar{\nu }$. Various NP models have been proposed to explain the data. In this talk, I discuss how the measurement of CP-violating observables in ${\bar{B}}^0\to D^{\ast +}{\ell }^{-}{\bar{\nu }}_{\ell }$ can be used to differentiate the NP scenarios.

   hep-phhep-ex1 citation
4. 04*

   Status of isospin splittings in mesons and baryons

   Marek Karliner🇮🇱 · Jonathan L. Rosner🇺🇸

   Current measurements of isospin splittings in mesons and baryons are sufficiently precise that they allow estimates of the mass difference between constituent up and down quarks. Some previous results are updated in the light of these new measurements, and the importance of better measurements of some observables such as $M(K^{\ast \pm })$, $M(B^{\ast 0})-M(B^0)$, and isospin splittings in bottom baryons is noted.

   hep-phhep-exPRD(2019)·17 citations
5. 05*

   Flavor changing Flavon decay $\varphi \to tc$ ($\varphi =H_F,A_F$) at the High Luminosity Large Hadron Collider

   M. A. Arroyo-Ureña🇲🇽 · A. Fernández-Téllez🇲🇽 · G. Tavares-Velasco🇲🇽

   We present a study of the flavor changing decays $\varphi \to tc$ ($\varphi =H_F,A_F$) of the $CP$-even and $CP$-odd scalar flavons at the large hadron collider and its next stage, the high-luminosity large hadron collider. The theoretical framework is an extension of the standard model that incorporates an extra complex singlet and invokes the Froggatt-Nielsen mechanism with an Abelian flavor symmetry. The projected exclusion and discovery regions in terms of the model parameters are reported. We find that $A_F$ could be detected at the LHC by considering a reasonable scenario of the model parameter space. As far as $H_F$ is concerned, we also found promising results that could be verified experimentally at the high-luminosity LHC.

   hep-phRev.Mex.Fis.(2023)·11 citations
6. 06*

   Algorithm to find an all-order in the running coupling solution to an equation of the DGLAP type

   Igor Kondrashuk🇨🇱

   We propose an algorithm to find a solution to an integro-differential equation of the DGLAP type for all the orders in the running coupling $\alpha$ with splitting functions given at a fixed order in $\alpha .$ Complex analysis is significantly used in the construction of the algorithm, we found a simpler way to calculate the involved integrals over contours in the complex planes than by any of the methods known at present.

   hep-phmath-phmath.MPPhys.Part.Nucl.Lett.(2021)·4 citations
7. 07*

   Visible narrow cusp structure in ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ enhanced by triangle singularity

   Xiao-Hai Liu🇨🇳 · Gang Li🇨🇳 · Ju-Jun Xie🇨🇳 · Qiang Zhao🇨🇳

   A resonance-like structure as narrow as 10 MeV is observed in the $K^{-}p$ invariant mass distributions in ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ at Belle. Based on the large data sample of about 1.5 million events and the small bin width of just 1 MeV for the $K^{-}p$ invariant mass spectrum, the narrow peak is found precisely lying at the $\Lambda \eta$ threshold. While lacking evidence for a quark model state with such a narrow width at this mass region, we find that this narrow structure can be naturally identified as a threshold cusp but enhanced by the nearby triangle singularity via the $\Lambda$-$a_0(980{)}^{+}$ or $\eta$-$\Sigma (1660{)}^{+}$ rescatterings.

   hep-phhep-exnucl-exnucl-thPRD(2019)·35 citations
8. 08*

   Di-jet/$e^{+}{e}^{-}$+ MET to Probe $Z_2-$Odd Mediators to the Dark Sector

   Florian Goertz🇩🇪 · Karla Tame-Narvaez🇩🇪 · Valentin Tenorth🇩🇪

   We explore a scenario where Dark Matter (DM) couples to the Standard Model mainly via a scalar mediator $\mathcal{S}$ that is odd under a $Z_2$ symmetry, leading to interesting collider signatures. In fact, if linear interactions with the mediator are absent the most important DM production mechanisms at colliders could lead to final states with missing transverse energy (MET) in association with at least two fermions, such as di-jet or di-electron signatures. The framework we consider is model-independent, in a sense that it is only based on symmetry and formulated in the (extended) DM Effective Field Theory (eDMEFT) approach. Moreover, it allows to address the smallness of first-generation fermion masses via suppressed $Z_2$ breaking effects. From a di-jet +MET analysis at the LHC, we find rather loose bounds on the effective $\mathcal{S}$-$\mathcal{S}$-DM-DM interactions, unless the mediator couples very strongly to SM fermions, while a future $e^{+}{e}^{-}$ collider, such as CLIC, could deliver tighter constraints on the corresponding model parameters, given the mediator is leptophilic. We finally highlight the parameter space that allows to produce the observed DM density, including constraints from direct-detection experiments.

   hep-phhep-exEPJC(2019)·8 citations
9. 09*

   New Physics in $b\to c\tau \nu$: Impact of Polarisation Observables and $B_c\to \tau \nu$

   Marta Moscati🇩🇪

   The experimental values of the lepton-flavour-universality tests $\mathcal{R}(D)$ and $\mathcal{R}(D^{\ast })$ show a tension of about $3.1\sigma$ with their Standard Model prediction. Motivated by this tension, we perform a fit of the $b\to c\tau \nu$ data. We consider one-particle scenarios imposing consecutive limits on $\text{BR}(B_c\to \tau {\nu }_{\tau })$, and analyse how these limits affect the fits. We include the polarisation observables available to date and predict those that are still to be measured, and conclude that they have a high model-resolving power. For each scenario we also predict $\mathcal{R}({\Lambda }_c)$, observing that an enhancement of $\mathcal{R}(D^{(\ast )})$ implies an enhancement of $\mathcal{R}({\Lambda }_c)$ in any scenario. We trace back this enhancement to a sum-rule valid irrespective of the scenario used to fit $\mathcal{R}(D^{(\ast )})$.

   hep-ph0 citations
10. 10*

    Electromagnetic properties of the nucleon and the Roper resonance in soft-wall AdS/QCD at finite temperature

    Thomas Gutsche🇩🇪 · Valery E. Lyubovitskij🇩🇪 · Ivan Schmidt🇨🇱

    We present a study of the nucleon electromagnetic form factors and of the Roper-nucleon transition at finite small temperature $T$, using an extended version of a soft-wall AdS/QCD approach developed by us previously. In the action we introduce the effective potential, which has quadratic dependence on the holographic coordinate $z$ and depends on both the gluon and quark condensates. Choosing the AdS geometry we restrict ourselves to the AdS Poincaré metric, because the contribution of the AdS-Schwarzschild geometry starts at next-to-leading order $\mathcal{O}(T^4)$. Hence, one can neglect the temperature dependence of the AdS geometry at small $T$. This is consistent with the Hawking-Page phase transition at a critical temperature representing the transition between thermal AdS/QCD and AdS-Schwarzschild geometry. In the small temperature regime we base our analysis on the temperature dependence of the effective potential, which starts at order $\mathcal{O}(T^2)$, due to the leading contribution from the quark condensate. As applications we present the analysis of properties of the nucleon and Roper resonance (masses, form factors, and helicity amplitudes) at low temperatures.

    hep-phNPB(2020)·24 citations
11. 11*

    Thermodynamics of quark-gluon plasma at finite baryon density

    Z.V Khaidukov🇷🇺 · Yu.A.Simonov🇷🇺

    Properties of the quark-gluon plasma(QGP) in the presence of the baryon chemical potential ${\mu }_B$ are studied using the Field Correlator Method(FCM). The nonperturbative FCM dynamics includes the Polyakov line, computed via colorelectric string tension ${\sigma }^E(T)$ and the quark and gluon Debye masses, defined by the colormagnetic string tension ${\sigma }^H(T)$. The resulting QGP thermodynamics at ${\mu }_B\le 400$ MeV is in a good agreement with the available lattice data,both pressure and the sound velocity do not show any sign of a critical behavior in this region.

    hep-phhep-latPRD(2019)·21 citations
12. 12*

    Constraining primordial black hole abundance with the Galactic 511 keV line

    William DeRocco🇺🇸 · Peter W. Graham🇺🇸

    Models in which dark matter consists entirely of primordial black holes (PBHs) with masses around $10^{17}$ g are currently unconstrained. However, if PBHs are a component of the Galactic dark matter density, they will inject a large flux of energetic particles into the Galaxy as they radiate. Positrons produced by these black holes will subsequently propagate throughout the Galaxy and annihilate, contributing to the Galactic 511 keV line. Using measurements of this line by the INTEGRAL satellite as a constraint on PBH positron injection, we place new limits on PBH abundance in the mass range $10^{16}-10^{17}$ g, ruling out models in which these PBHs constitute the entirety of dark matter.

    ↳ astro-ph.COhep-phPRL(2019)·212 citations
13. 13*

    On the self-consistency of off-shell Slavnov-Taylor identities in QCD

    J.A. Gracey🇬🇧 · H. Kissler🇩🇪 · D. Kreimer🇩🇪

    Using Hopf-algebraic structures as well as diagrammatic techniques for determining the Slavnov-Taylor identities for QCD we construct the relations for the triple and quartic gluon vertices at one loop. By making the longitudinal projection on an external gluon of a Green's function we show that the gluon self-energy of that leg is consistently replaced by a ghost self-energy. The resulting identities are then studied by evaluating all the graphs for an off-shell non-exceptional momentum configuration. In the case of the 3-point function this is for the most general momentum case and for the 4-point function we consider the fully symmetric point.

    ↳ hep-thhep-phPRD(2019)·20 citations
14. 14*

    Revisiting instabilities of $S^1/Z_2$ models with loop-induced Fayet-Iliopoulos terms

    Hiroyuki Abe🇯🇵 · Tatsuo Kobayashi🇯🇵 · Shohei Uemura🇯🇵 · Junji Yamamoto🇯🇵

    We study Fayet-Iliopoulos (FI) terms of 5-dimensional supersymmetric $U(1)$ gauge theory compactified on $S^1/Z_2$. In this model, loop diagrams including matter hypermultiplets and brane chiral multiplets induce FI-terms localized at the fixed points. Localized FI-terms lead instabilities of bulk modes. The form of the induced FI-terms strictly depends on wave function profiles of matter multiplets. It is a non-trivial question whether the vacuum of 1-loop corrected potential is stable under radiative corrections. We investigate this issue and it is found that the stable configuration is obtained when the bulk zero modes shield the brane charge completely.

    ↳ hep-thhep-phPRD(2019)·2 citations
15. 15*

    Flux Tube S-matrix Bootstrap

    Joan Elias Miro🇨🇭 · Andrea L. Guerrieri🇧🇷 · Aditya Hebbar🇨🇭 · Joao Penedones🇨🇭 · Pedro Vieira🇨🇦

    We bootstrap the S-matrix of massless particles in unitary, relativistic two dimensional quantum field theories. We find that the low energy expansion of such S-matrices is strongly constrained by the existence of a UV completion. In the context of flux tube physics, this allows us to constrain several terms in the S-matrix low energy expansion or -- equivalently -- on Wilson coefficients of several irrelevant operators showing up in the flux tube effective action. These bounds have direct implications for other physical quantities; for instance, they allow us to further bound the ground state energy as well as the level splitting of degenerate energy levels of large flux tubes. We find that the S-matrices living at the boundary of the allowed space exhibit an intricate pattern of resonances with one sharper resonance whose quantum numbers, mass and width are precisely those of the world-sheet axion proposed in [1,2]. The general method proposed here should be extendable to massless S-matrices in higher dimensions and should lead to new quantitative bounds on irrelevant operators in theories of Goldstones and also in gauge and gravity theories.

    ↳ hep-thhep-lathep-phnlin.SIPRL(2019)·92 citations
16. 16*

    Weak-field limit of Kaluza-Klein model with non-linear perfect fluid

    Ezgi Yalçınkaya🇹🇷 · Alexander Zhuk🇹🇷

    The main purpose of our paper is to construct a viable Kaluza-Klein model satisfying the observable constraints. To this end, we investigate the six-dimensional model with spherical compactification of the internal space. Background matter is considered in the form of a perfect fluid with non-linear equations of state both in the external/our and internal spaces and the model is set to include an additional bare cosmological constant ${\Lambda }_6$. In the weak-field approximation, the background is perturbed by pressureless gravitating mass that is a static point-like particle. The non-linearity of the equations of state of a perfect fluid makes it possible to solve simultaneously a number of problems. The demand that the parameterized post-Newtonian parameter $\gamma$ be equal to 1 in this configuration, first, ensures compatibility with gravitational tests in the Solar system (deflection of light and time delay of radar echoes) at the same level of accuracy as General Relativity. Second, it translates into the absence of internal space variations so that the gravitational potential coincides exactly with the Newtonian one, securing the absence of the fifth force. Third, the gravitating mass remains pressurless in the external space as in the standard approach to non-relativistic astrophysical objects and meanwhile, acquires effective tension in the internal space.

    ↳ gr-qcastro-ph.COhep-phhep-thGrav.Cosmol.(2019)·2 citations
17. 17*

    Cosmic Conundra Explained by Thermal History and Primordial Black Holes

    Bernard Carr🇬🇧 · Sebastien Clesse🇧🇪 · Juan Garcia-Bellido🇪🇸 · Florian Kuhnel🇩🇪

    A universal mechanism may be responsible for several unresolved cosmic conundra. The sudden drop in the pressure of relativistic matter at $W^{\pm }/Z^0$ decoupling, the quark--hadron transition and $e^{+}{e}^{-}$ annihilation enhances the probability of primordial black hole (PBH) formation in the early Universe. Assuming the amplitude of the primordial curvature fluctuations is approximately scale-invariant, this implies a multi-modal PBH mass spectrum with peaks at $10^{-6}$, 1, 30, and $10^6{M}_{\odot }$. This suggests a unified PBH scenario which naturally explains the dark matter and recent microlensing observations, the LIGO/Virgo black hole mergers, the correlations in the cosmic infrared and X-ray backgrounds, and the origin of the supermassive black holes in galactic nuclei at high redshift. A distinctive prediction of our model is that LIGO/Virgo should observe black hole mergers in the mass gaps between 2 and $5M_{\odot }$ (where no stellar remnants are expected) and above $65M_{\odot }$ (where pair-instability supernovae occur) and low-mass-ratios in between. Therefore the recent detection of events GW190425, GW190814 and GW190521 with these features is striking confirmation of our prediction and may indicate a primordial origin for the black holes. In this case, the exponential sensitivity of the PBH abundance to the equation of state would offer a unique probe of the QCD phase transition. The detection of PBHs would also offer a novel way to probe the existence of new particles or phase transitions with energy between $1\mathrm{MeV}$ and $10^{10}$GeV.

    ↳ astro-ph.COgr-qchep-phhep-thPhys.Dark Univ.(2021)·280 citations
18. 18*

    New constraints on Lorentz Invariance violation from Crab Nebula spectrum beyond $100$ TeV

    Petr Satunin🇷🇺

    Recently two collaborations, Tibet and HAWC, presented new measurements of gamma-ray spectrum from Crab Nebula \cite{Amenomori:2019rjd},\cite{Abeysekara:2019edl} which continues beyond $100$ TeV. We use these data to establish two-sided constraints on parameters of Lorentz Invariance violation in quantum electrodynamics. The limits on Lorentz violating mass scale for quartic dispersion relation are $4.1\times 10^{14}\text{mbox}GeV$ (photon splitting) and $1.9\times 10^{13}\text{mbox}GeV$ (photon decay) for superluminal case, and $1.4\times 10^{12}$ GeV (suppression of shower formation) for subluminal case.

    ↳ astro-ph.HEhep-phEPJC(2019)·34 citations
19. 19*

    $H_0$ Tension, Swampland Conjectures and the Epoch of Fading Dark Matter

    Prateek Agrawal🇺🇸 · Georges Obied🇺🇸 · Cumrun Vafa🇺🇸

    Motivated by the swampland dS conjecture, we consider a rolling scalar field as the source of dark energy. Furthermore, the swampland distance conjecture suggests that the rolling field will lead at late times to an exponentially light tower of states. Identifying this tower as residing in the dark sector suggests a natural coupling of the scalar field to the dark matter, leading to a continually reducing dark matter mass as the scalar field rolls in the recent cosmological epoch. The exponent in the distance conjecture, $\tilde{c}$, is expected to be an $\mathcal{O}(1)$ number. Interestingly, when we include the local measurement of $H_0$, our model prefers a non-zero value of the coupling $\tilde{c}$ with a significance of $2.8\sigma$ and a best-fit at $\tilde{c}\sim 0.3$. Modifying the recent evolution of the universe in this way improves the fit to data at the $2\sigma$ level compared to $\Lambda$CDM. This string-inspired model automatically reduces cosmological tensions in the $H_0$ measurement as well as ${\sigma }_8$.

    ↳ astro-ph.COhep-phhep-thPRD(2021)·137 citations
20. 20*

    A Simple Phenomenological Emergent Dark Energy Model can Resolve the Hubble Tension

    Xiaolei Li🇰🇷 · Arman Shafieloo🇰🇷

    Motivated by the current status of the cosmological observations and significant tensions in the estimated values of some key parameters assuming the standard $\Lambda$CDM model, we propose a simple but radical phenomenological emergent dark energy model where dark energy has no effective presence in the past and emerges at the later times. Theoretically, in this phenomenological dark energy model with zero degree of freedom (similar to a $\Lambda$CDM model), one can derive that the equation of state of dark energy increases from $-\frac{2}{3\ln 10}-1$ in the past to $-1$ in the future. We show that by setting a hard-cut 2$\sigma$ lower bound prior for the $H_0$ that associates with $97.72\%$ probability from the recent local observations~\citep{riess2019large}, this model can satisfy different combinations of cosmological observations at low and high redshifts (SNe Ia, BAO, Ly{$\alpha$} BAO and CMB) substantially better than the concordance $\Lambda$CDM model with $\Delta {\chi }_{bf}^2\sim -41.08$ and $\Delta \mathrm{DIC}\sim -35.38$. If there are no substantial systematics in SN Ia, BAO or Planck CMB data and assuming reliability of the current local $H_0$ measurements, there is a very high probability that with slightly more precise measurement of the Hubble constant our proposed phenomenological model rules out the cosmological constant with decisive statistical significance and is a strong alternative to explain combination of different cosmological observations. This simple phenomenologically emergent dark energy model can guide theoretically motivated dark energy model building activities.

    ↳ astro-ph.COgr-qchep-phhep-thApJL(2019)·256 citations
21. 21*

    Electromagnetic stress on nucleon structure

    Benjamin Koch🇨🇱

    External electromagnetic fields can provoke stress, and thus modifications of the internal structure of nucleons. Working with this hypothesis, one can derive a simple description of the charge dependence of the EMC effect. This first result is confirmed by two explicit models of the structure functions of deformed nucleons in the atomic nucleus. For large nuclei a continuous model is used. For small nuclei a discrete distribution of nuclear matter gives better results.

    ↳ nucl-thhep-phNPA(2020)·1 citation
22. 22*

    Mass spectra in $\mathcal{N}=1SQCD$ with additional colorless but flavored fields

    Victor L. Chernyak🇷🇺

    Considered is the $\mathcal{N}=1$ SQCD-like theory with $SU(N_c)$ colors and $0<N_F<2N_c$ flavors of equal mass $0<m_Q\ll {\Lambda }_Q$ quarks. Besides, it includes $N_F^2$ additional colorless but flavored fields ${\Phi }_i^j$, with the large mass parameter ${\mu }_{\Phi }\gg {\Lambda }_Q$. The mass spectra of this $\Phi$-theory are first directly calculated at $0<N_F<N_c$ where the quarks are weakly coupled, in all different vacua with the unbroken or spontaneously broken flavor symmetry $U(N_F)\to U(n_1)\times U(n_2)$. Further, the mass spectra of this direct $\Phi$-theory and its Seiberg's dual variant, the $d\Phi$-theory, are calculated at $3N_c/2<N_F<2N_c$ and various values of ${\mu }_{\Phi }/{\Lambda }_Q\gg 1$ (in strong coupling regimes), using the dynamical scenario introduced by the author in his previous article \cite{ch3}. This scenario assumes that quarks can be in two different standard phases only: either this is the HQ (heavy quark) phase where they are confined, or they are higgsed. Within the used dynamical scenario, it is shown that mass spectra of the direct $\Phi$ and dual $d\Phi$ - theories are parametrically different. Besides it is shown in the direct $\Phi$-theory that a qualitatively new phenomenon takes place: under appropriate conditions, the seemingly heavy and dynamically irrelevant fields $\Phi$ 'return back' and there appear two additional generations of light $\Phi$-particles with small masses ${\mu }^{\mathrm{pole}}(\Phi )\ll {\Lambda }_Q$. Also considered is the $X$-theory which is the $\mathcal{N}=2$ SQCD with $SU(N_c)$ colors and $0<N_F<2N_c$ flavors of light quarks, broken down to $\mathcal{N}=1$ by the large mass parameter of the adjoint scalar superfield $X,{\mu }_X\gg {\Lambda }_2$. The tight interrelations between these $X$ and $\Phi$ theories are described, in particular, the conditions under which they are equivalent.

    ↳ hep-thhep-phEPJC(2017)·8 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.