Tue·Apr 30, 2019Tuesday·April 30, 2019

1. 01*

   Resolving the degeneracy in top quark Yukawa coupling with Higgs pair production

   Gang Li🇹🇼 · Ling-Xiao Xu🇨🇳 · Bin Yan🇺🇸 · C.-P. Yuan🇺🇸

   The top quark Yukawa coupling ($y_t$) can be modified by two dimension-six operators ${\mathcal{O}}_H$ and ${\mathcal{O}}_y$ with the corresponding Wilson coefficients $c_H$ and $c_y$, whose individual contribution cannot be distinguished by measuring $y_t$ alone. However, such a degeneracy can be resolved with Higgs boson pair production. In this work we explore the potential of resolving the degeneracy of the unknown Wilson coefficients $c_H$ and $c_y$ at the 14~TeV LHC and the 100~TeV hadron colliders. Combining the information of the single Higgs production, $t\bar{t}h$ associated production and Higgs pair production, the individual contribution of $c_H$ and $c_y$ to $y_t$ can be separated. Regardless of the value of $c_H$, the Higgs pair production can give a strong constraint on $c_y$ at the 100 TeV hadron collider. We further show that it is possible to differentiate various $c_y$ and $c_t$ values predicted in several benchmark models.

   hep-phhep-exPLB(2020)·30 citations
2. 02*

   Hadronic and hadron-like physics of Dark Matter

   Vitaly Beylin🇷🇺 · Maxim Yu. Khlopov🇷🇺 · Vladimir Kuksa🇷🇺 · Nikolay Volchanskiy🇷🇺

   The problems of simple elementary weakly interacting massive particles (WIMPs) appeal to extend the physical basis for nonbaryonic dark matter. Such extension involves more sophisticated dark matter candidates from physics beyond the Standard Model (BSM) of elementary particles. We discuss several models of dark matter, predicting new colored, hyper-colored or techni-colored particles and their accelerator and non-accelerator probes. The nontrivial properties of the proposed dark matter candidates can shed new light on the dark matter physics. They provide interesting solutions for the puzzles of direct and indirect dark matter search.

   hep-phSymmetry(2019)·47 citations
3. 03*

   Fate of the Landau-Yang theorem for twisted photons

   Igor P. Ivanov🇵🇹 · Valery G. Serbo🇷🇺 · Pengming Zhang🇨🇳

   Landau-Yang theorem is sometimes formulated as a selection rule forbidding two real (that is, non-virtual) photons with zero total momentum to be in the state of the total angular momentum J=1. In this paper we discuss whether the theorem itself and this particular formulation can be extended to a pair of two {\em twisted} photons, which carry orbital angular momentum with respect to their propagation direction. We point out possible sources of confusion, which may arise both from the unusual features of twisted photons and from the fact that usual proofs of the Landau-Yang theorem operate in the center of motion reference frame, which, strictly speaking, exists only for plane waves. We show with an explicit calculation that a pair of twisted photons does have a non-zero overlap with the J=1 state. What is actually forbidden is production of a spin-1 particle by such a photon pair, and in this formulation the Landau-Yang theorem is rock-solid. Although both the twisted photon pair and the spin-1 particle can exist in the J=1 state, these two systems just cannot be coupled in a gauge-invariant and Lorentz invariant manner respecting Bose symmetry.

   hep-phJ.Opt.(2019)·9 citations
4. 04*

   Azimuthal asymmetries from $\theta$ Vacuum

   Weihua Yang🇨🇳

   We present the complete azimuthal asymmetries at leading twist in terms of fragmentation functions in dihadron production semi-inclusive electron positron annihilation process. When the non-trivial $\theta$ vacuum is taken into consideration, the parity symmetry of quantum chromodynamics is violated. As a consequence of the $local$ $\mathcal{P}$-odd effects, $\mathcal{P}$-odd fragmentation functions would contribute to the azimuthal asymmetries. Azimuthal asymmetry coming from two interference terms with opposite signs vanishes when sum over many events. This symmetry only survives on the event-by-event basis. Azimuthal asymmetry coming from two interference terms with same signs survives and can be measured to extract the $\mathcal{P}$-odd fragmentation functions. We also present the hadron polarizations.

   hep-phInt.J.Mod.Phys.A(2019)·8 citations
5. 05*

   Testing the tetraquark mixing framework from QCD sum rules for $a_0(980)$

   Hee-Jung Lee🇰🇷 · K. S. Kim🇰🇷 · Hungchong Kim🇰🇷

   According to a recent proposal of the tetraquark mixing framework, the two light-meson nonets in the $J^P=0^{+}$ channel, namely the light nonet composed of $a_0(980)$, $K_0^{\ast }(800)$, $f_0(500)$, $f_0(980)$, and the heavy nonet of $a_0(1450)$, $K_0^{\ast }(1430)$, $f_0(1370)$, $f_0(1500)$, can be expressed by linear combinations of the two tetraquark types, one type containing the spin-0 diquark and the other with the spin-1 diquark. Among various consequences of this mixing model, one surprising result is that the second tetraquark with the spin-1 diquark configuration is more important for the light nonet. In this work, we report that this result can be supported by the QCD sum rule calculation. In particular, we construct a QCD sum rule for the isovector resonance $a_0(980)$ using an interpolating field composed of both tetraquark types and then perform the operator product expansion up to dimension 10 operators. Our sum rule analysis shows that the spin-1 diquark configuration is crucial in generating the $a_0(980)$ mass. Also, the mixed correlation function constructed from the two tetraquark types is found to have large strength which seems consistent with what the tetraquark mixing framework is advocating. On the other hand, the correlation function from the interpolating field with the spin-0 diquark configuration alone fails to predict the $a_0(980)$ mass mostly by the huge negative contribution from dimension 8 operators.

   hep-phhep-exhep-latnucl-thPRD(2019)·18 citations
6. 06*

   Probing the Decoupled Seesaw Scalar in Rare Higgs Decay

   Yu Gao🇨🇳 · Mingjie Jin🇨🇳 · Kechen Wang🇨🇳

   The Higgs boson can mix with a singlet scalar that dynamically generates the Majorana mass of the right-handed neutrino $N_R$. We show that even a tiny mixing between the Higgs boson and a `decoupled' singlet scalar allows for Higgs-mediated pair production of $N_R$ without significant mixings between the active neutrinos and $N_R$, and thus testable at colliders via a characteristic signal of two same-sign same-flavor lepton pairs, plus missing energy. We demonstrate that this search channel is mostly background-free in $pp$-collision and can be a highly sensitive probe of the Higgs-singlet mixing at the current and future $pp$ colliders. Such channel provides a clean signal to discover the singlet scalar and explore the origin of neutrino masses.

   hep-phhep-exJHEP(2020)·10 citations
7. 07*

   Cosmological decay of Higgs-like scalars into a fermion channel

   Daniel Boyanovsky🇺🇸 · Nathan Herring🇺🇸

   We study the decay of a Higgs-like scalar Yukawa coupled to massless fermions in post-inflationary cosmology, combining a non-perturbative method with an adiabatic expansion. The renormalized survival probability ${\mathcal{P}}_{\Phi }(t)$ of a (quasi) particle ``born'' at time $t_b$ and decaying at rest in the comoving frame, ${\mathcal{P}}_{\Phi }(t)=[\frac{t}{t_b}{]}^{-\frac{Y^2}{8{\pi }^2}}{e}^{\frac{Y^2}{4{\pi }^2}(t/t_b{)}^{1/4}}{e}^{-{\Gamma }_0(t-t_b)}{\mathcal{P}}_{\Phi }(t_b)$, with ${\Gamma }_0$ the decay rate at rest in Minkowski space-time. For an ultrarelativistic particle we find ${\mathcal{P}}_{\Phi }(t)=e^{-\frac{2}{3}{\Gamma }_0{t}_{nr}(t/t_{nr}{)}^{3/2}}{\mathcal{P}}_{\Phi }(t_b)$ before it becomes non-relativistic at a time $t_{nr}$ as a consequence of the cosmological redshift. For $t\gg t_{nr}$ we find ${\mathcal{P}}_{\Phi }(t)=\left[\frac{t}{t_{nr}}{]}^{-\frac{Y^2}{8{\pi }^2}}{e}^{\frac{Y^2}{4{\pi }^2}(t/t_{nr}{)}^{1/4}}\right[\frac{t}{t_{nr}}{]}^{{\Gamma }_0{t}_{nr}/2}{e}^{-{\Gamma }_0(t-t_{nr})}{\mathcal{P}}_{\Phi }(t_{nr})$. The extra power is a consequence of the memory on the past history of the decay process. We compare these results to an S-matrix inspired phenomenological Minkowski-like decay law modified by an instantaneous Lorentz factor to account for cosmological redshift. Such phenomenological description \emph{under estimates the lifetime of the particle}. For very long lived, very weakly coupled particles, we obtain an \emph{upper bound} for the survival probability as a function of redshift $z$ valid throughout the expansion history ${\mathcal{P}}_{\Phi }(z)\gtrsim e^{-\frac{{\Gamma }_0}{H_0}{\rm Y}(z,z_b)}{\mathcal{P}}_{\Phi }(z_b)$, where ${\rm Y}(z,z_b)$ only depends on cosmological parameters and $t_{nr}$.

   hep-phastro-ph.COgr-qchep-thPRD(2019)·10 citations
8. 08*

   NuOscProbExact: a fast, general-purpose code to compute exact two-, three-, and four-flavor neutrino oscillation probabilities

   Mauricio Bustamante (Bohr Inst.)🇩🇰

   A neutrino created with one flavor can oscillate and be detected later with another. Ordinarily, the probability of this occurring---the oscillation probability---is obtained by diagonalizing the Hamiltonian that drives the neutrino evolution. We bypass the diagonalization: expanding the evolution operator in the generators of the groups SU(2), SU(3), and SU(4) yields exact closed-form probabilities for two, three, and four neutrino flavors that need the eigenvalues of the Hamiltonian and never its eigenvectors. As a result, every probability is then the same short run of arithmetic, whatever the Hamiltonian contains. We implement these expressions in NuOscProbExact, which we make publicly available. Any scenario with a time- or position-independent Hermitian Hamiltonian is in scope: oscillations in vacuum, matter of constant density, with non-standard interactions, in a Lorentz-violating background, with sterile states, combinations of them, or completely novel theory proposals. Matter of piecewise constant density, including the density profile of Earth, follows by composing the exact solutions for consecutive matter slabs. NuOscProbExact offers three properties that are seldom found in one program. It is flexible: computing probabilities for a new oscillation scenario needs no new solver, only a new Hamiltonian matrix. It is fast: among the surveyed existing public oscillation codes, it is the quickest to compute probabilities for neutrinos going through the Earth at every accuracy but the coarsest. It is accurate: for the Hamiltonian it is given, only machine round-off limits the probability; at constant density, no other surveyed code comes within four decades of it. Deriving only a Hamiltonian, and evaluating a million of them in one call, puts whole parameter spaces within reach in scenarios that no approximation covers.

   hep-phastro-ph.HEhep-ex15 citations
9. 09*

   Prospects for CP & P violation in ${\Lambda }_c^{+}$ decay at STCF

   Xiao-Dong Shi🇨🇳 · Xian-Wei Kang🇨🇳 · Ikaros Bigi🇺🇸 · Wei-Ping Wang🇨🇳 · Hai-Ping Peng🇨🇳

   CP violation is an excellent tool for probing flavor dynamics as we learnt first with $K_L\to 2\pi$ and later also with the weak decays of beauty mesons. LHCb 2019 data have shown CP violation for the first time in $D^0\to K^{-}{K}^{+}$ vs. $D^0\to {\pi }^{-}{\pi }^{+}$. Searching for CP asymmetries is of great interest in charm quark sector in the Standard Model (SM) or even more beyond it. In charm hadron decays, lots of work had focused on two-body final states, and the measurements of CP asymmetries in three- or four-body final states are rare. Dalitz plots have shown an excellent record for three-body final states, and more results are desired for four-body ones. In this work we study CP asymmetries in the decays ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}{\pi }^0$/$\Lambda {\pi }^{+}{\pi }^{+}{\pi }^{-}$/$p{K}_S{\pi }^{+}{\pi }^{-}$, where the SM gives zero values for the first two channels, while $3.3\times 10^{-3}$ for the last one due to $K^0-{\bar{K}}^0$ oscillation. We performed a fast Monte Carlo simulation study by using electron-positron annihilation data of 1~${\text{ab}}^{-1}$ at center-of-mass energy $\sqrt{s}=4.64$ GeV. The data is expected to be available by the next generation Super Tau Charm Facility proposed by China and Russia with one year (or even less) data taking operation. The results indicate that a sensitivity at the level of 0.2$\sim$0.5% is accessible for these processes, which would be enough to measure nonzero CP-violating asymmetries as large as 1%.

   hep-phhep-exPRD(2019)·22 citations
10. 10*

    Differential equations, recurrence relations, and quadratic constraints for $L$-loop two-point massive tadpoles and propagators

    Roman N. Lee🇷🇺 · Andrei A. Pomeransky🇷🇺

    We consider $L$-loop two-point tadpole (watermelon) integral with arbitrary masses, regularized both dimensionally and analytically. We derive differential equation system and recurrence relations (shifts of dimension and denominator powers). Since the $L$-loop sunrise integral corresponds to the $(L+1)$-loop watermelon integral with one cut line, our results are equally applicable to the former. The obtained differential system has a Pfaffian form and is linear in dimension and analytic regularization parameters. In general case, the solutions of this system can be expressed in terms of the Lauricella functions $F_C^{(L)}$ with generic parameters. Therefore, as a by-product, we obtain, to our knowledge for the first time, the Pfaffian system for $F_C^{(L)}$ for arbitrary $L$. The obtained system has no apparent singularities. Near odd dimension and integer denominator powers the system can be easily transformed into canonical form. Using the symmetry properties of the matrix in the right-hand side of the differential system, we obtain quadratic constraints for the expansion of solutions near integer dimension and denominator powers. In particular, we obtain quadratic constraints for Bessel moments similar to those discovered by Broadhurst and Roberts.

    hep-phhep-thmath-phmath.MPJHEP(2019)·12 citations
11. 11*

    Clockwork origin of neutrino mixings

    Teruyuki Kitabayashi🇯🇵

    The clockwork mechanism provides a natural way to obtain hierarchical masses and couplings in a theory. We propose a clockwork model that has nine clockwork generations. In this model, the candidates of the origin of the neutrino mixings are nine Yukawa mass matrix elements $Y^{a\beta }$ that connect neutrinos and clockwork fermions, nine clockwork mass ratios $q_{a\beta }$, and nine numbers of clockwork fermions $n_{a\beta }$, where $a,\beta =1,2,3$. Assuming $|Y^{a\beta }|=1$, the neutrino mixings originate from the pure clockwork sector. We show that the observed neutrino mixings are exactly obtained from a clockwork model in the case of the $q_{a\beta }$ origin scenario. In the $n_{a\beta }$ origin scenario, the correct order of magnitude of the observed neutrino mixings is obtained from a clockwork model.

    hep-phPRD(2019)·11 citations
12. 12*

    High energy muons in extensive air showers

    Carmen Gámez🇪🇸 · Miguel Gutiérrez🇨🇴 · Juan S. Martínez🇪🇸 · Manuel Masip🇪🇸

    The production of very high energy muons inside an extensive air shower is observable at $\nu$ telescopes and sensitive to the composition of the primary cosmic ray. Here we discuss five different sources of these muons: pion and kaon decays; charmed hadron decays; rare decays of unflavored mesons; photon conversion into a muon pair; and photon conversion into a $J/\psi$ vector meson decaying into muons. We solve the cascade equations for a $10^{10.5}$ GeV proton primary and find that unflavored mesons and gamma conversions are the two main sources of $E\ge 10^{8.5}$ GeV muons, while charm decays dominate at $10^{5.5}\mathrm{GeV}<E<10^{8.5}\mathrm{GeV}$. In inclined events one of these muons may deposite a large fraction of its energy near the surface, implying fluctuations in the longitudinal profile of the shower and in the muon to electron count at the ground level. In particular, we show that 1 out of 6 proton showers of $10^{10.5}$ GeV include an $E>10^6$ GeV deposition within 500 g/cm${}^2$, while only in 1 out of 330 showers it is above $10^7$ GeV. We also show that the production of high energy muons is very different in proton, iron or photon showers ({e.g., conversions $\gamma \to {\mu }^{+}{\mu }^{-}$ are the main source of $E\ge 10^4$ GeV muons in photon showers). Finally, we use Monte Carlo simulations to discuss the validity of our results.

    hep-phastro-ph.HEJCAP(2020)·11 citations
13. 13*

    Probing new physics in rare decays of b-flavored Hadrons $b\to s\gamma$ in CMSSM/mSUGRA SUSY SO (10) theories

    Gayatri Ghosh🇮🇳

    The implications of the latest measurement of the branching fraction of B($b\to s\gamma$) of b hadrons, which is another signature of New Physics beyond Standard Model is presented here. The quark transitions $b\to s$, $b\to d$ do not happen at tree level in the Standard Model as the Z boson does not couple to quarks of different flavour. In this work the present bounds on the quark transition $b\to s$ within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which there are three independent soft SUSY breaking parameters $m_0$, $m_{1/2}$ and $A_0$ is illustrated. The recent constraint on B($b\to s\gamma$), B($b_s\to {\mu }^{+}{\mu }^{-}$), the recently measured value of Higgs mass at LHC, $M_h$, the value of ${\theta }_{13}$ from reactor data and the Higgs branching ratios set very strong constraints on New Physics models, in particular supersymmetry. A new epoch for this research has begun since the Large Hadron Collider beauty (LHCb) experiment started affording data for various observables for these decays. The results presented here in mSUGRA/CMSSM models may gain access to supersymmetry even at scales beyond the direct reach of the LHC and the susceptibleness to test these theories at the next run of LHC is also explored.

    hep-phGradiva,ISSN:0363-8057,87-99, VOLUME-8-IS…·0 citations
14. 14*

    Majorana neutrino masses in gauge-Higgs unification

    K. Hasegawa🇯🇵

    The theory that the extra-space component of the gauge field is identified with the standard model Higgs boson, is called the gauge-Higgs unification (GHU) scenario. We examine how the small neutrino masses are naturally generated in the GHU framework. We find out two model classes where the following matter multiplets are introduced : 1. adjoint rep. lepton ${\Psi }_A$, 2. fundamental rep. lepton ${\Psi }_F$ and scalar ${\Sigma }_F$. We present a concrete model in each class. At the model in class 1, the neutrino masses are generated by the admixture of the seesaw mechanism type-I and -III. At the model in class 2, the masses are generated by the inverse seesaw mechanism.

    hep-phPoS(2019)·0 citations
15. 15*

    A background estimator for jet studies in p+p and A+A collisions

    Yacine Mehtar-Tani🇺🇸 · Alba Soto-Ontoso🇺🇸 · Marta Verweij🇺🇸

    Experimentally, jet physics studies face an unavoidable task: distinguishing, at the detector level, the particles produced in the hard partonic scattering from the ones created in unrelated soft processes such as pileup interactions in high-luminosity proton-proton scattering or the underlying event in heavy-ion collisions. The fluctuating nature of the background constitutes the main source of uncertainty for any subtraction algorithm. Aiming at mitigating the effect of such fluctuations, we present a new method to estimate the background contribution to the transverse momentum on a jet-by-jet basis. Our approach is based on estimating the median background momentum density stored above a $p_{\mathrm{T}}$-cut applied at the constituent level and an experimentally accessible correction term related to the signal contribution below the cut. This allows to trade part of the uncertainty due to background contamination for that of the signal below the cut, similarly to SoftKiller method. We propose to reduce the fluctuations of the latter by exploiting intrinsic correlations among the soft and hard sectors of QCD jets. Our data-driven approach is tested against PYTHIA8 and JEWEL di-jet events embedded in a thermal background and compared to the area-median and SoftKiller methods. The main result of this study is a $\sim 5-40\%$ improvement on the resolution of the reconstructed jet $p_T$ compared to previous methods in a high-luminosity proton-proton scenario. Its applicability in a heavy-ion context is also discussed.

    hep-phhep-exnucl-exnucl-thPRD(2019)·3 citations
16. 16*

    Two-Loop Massive Quark Jet Functions in SCET

    André H. Hoang🇦🇹 · Christopher Lepenik🇦🇹 · Maximilian Stahlhofen🇩🇪

    We calculate the $\mathcal{O}({\alpha }_s^2)$ corrections to the primary massive quark jet functions in Soft-Collinear Effective Theory (SCET). They are an important ingredient in factorized predictions for inclusive jet mass cross sections initiated by massive quarks emerging from a hard interaction with smooth quark mass dependence. Due to the effects coming from the secondary production of massive quark-antiquark pairs there are two options to define the SCET jet function, which we call universal and mass mode jet functions. They are related to whether or not a soft mass mode (zero) bin subtraction is applied for the secondary massive quark contributions and differ in particular concerning the infrared behavior for vanishing quark mass. We advocate that a useful alternative to the common zero-bin subtraction concept is to define the SCET jet functions through subtractions related to collinear-soft matrix elements. This avoids the need to impose additional power counting arguments as required for zero-bin subtractions. We demonstrate how the two SCET jet function definitions may be used in the context of two recently developed factorization approaches to treat secondary massive quark effects. We clarify the relation between these approaches and in which way they are equivalent. Our two-loop calculation involves interesting technical subtleties related to spurious rapidity divergences and infrared regularization in the presence of massive quarks.

    hep-phhep-thJHEP(2019)·30 citations
17. 17*

    Self-Similarity and Criticality in the Boson (pions) field produced according to dynamic cascade models

    Yiannis Contoyiannis🇮🇳 · Myron Kampitakis🇮🇳

    In this work we reveal that the inside-outside dynamic model for the production of fermion-antifermion pair (or quark-antiquark in QCD), is an out of equilibrium process. Properties of a complex system as the self-similarity and the critical point of a continuous phase transition in equilibrium appear. In this work we show that this is accomplished imposing a type of mapping process through a self-composition operator on a QED_2 bosons (or pions) field.

    hep-phcond-mat.stat-mech0 citations
18. 18*

    Ultrafast Polarization of an Electron Beam in an Intense Bi-chromatic Laser Field

    Daniel Seipt🇺🇸 · Dario Del Sorbo🇺🇸 · Christopher P. Ridgers🇬🇧 · Alec G. R. Thomas🇺🇸

    Here, we demonstrate the radiative polarization of high-energy electron beams in collisions with ultrashort pulsed bi-chromatic laser fields. Employing a Boltzmann kinetic approach for the electron distribution allows us to simulate the beam polarization over a wide range of parameters and determine the optimum conditions for maximum radiative polarization. Those results are contrasted with a Monte-Carlo algorithm where photon emission and associated spin effects are treated fully quantum mechanically using spin-dependent photon emission rates. The latter method includes realistic focusing laser fields, which allows us to simulate a near-term experimentally feasible scenario of a 8 GeV electron beam scattering from a 1 PW laser pulse and provide a measurement that would verify the ultrafast radiative polarization in high-intensity laser pulses that we predict. Aspects of spin dependent radiation reaction are also discussed, with spin polarization leading to a measurable (5%) splitting of the energies of spin-up and spin-down electrons.

    ↳ physics.plasm-phhep-phphysics.acc-phPRA(2019)·65 citations
19. 19*

    First measurements of absolute branching fractions of the ${\Xi }_c^{+}$ baryon at Belle

    Belle Collaboration: Y.B.Li🇨🇳 · C.P.Shen🇨🇳 · I. Adachi🇯🇵 · J. K. Ahn🇰🇷 · H. Aihara🇯🇵 · S. Al Said🇸🇦 · D. M. Asner🇺🇸 · H. Atmacan🇺🇸 · T. Aushev🇷🇺 · R. Ayad🇸🇦 · V. Babu🇩🇪 · A. M. Bakich🇦🇺 and 182 other authors

    We present the first measurements of the absolute branching fractions of ${\Xi }_c^{+}$ decays into ${\Xi }^{-}{\pi }^{+}{\pi }^{+}$ and $p{K}^{-}{\pi }^{+}$ final states. Our analysis is based on a data set of $(772\pm 11)\times 10^6$ $B\bar{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. We measure the absolute branching fraction of ${\bar{B}}^0\to {\bar{\Lambda }}_c^{-}{\Xi }_c^{+}$ with the ${\Xi }_c^{+}$ recoiling against ${\bar{\Lambda }}_c^{-}$ in ${\bar{B}}^0$ decays resulting in $\mathcal{B}({\bar{B}}^0\to {\bar{\Lambda }}_c^{-}{\Xi }_c^{+})=[1.16\pm 0.42(stat.)\pm 0.15(syst.)]\times 10^{-3}$. We then measure the product branching fractions $\mathcal{B}({\bar{B}}^0\to {\bar{\Lambda }}_c^{-}{\Xi }_c^{+})\mathcal{B}({\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+})$ and $\mathcal{B}({\bar{B}}^0\to {\bar{\Lambda }}_c^{-}{\Xi }_c^{+})\mathcal{B}({\Xi }_c^{+}\to p{K}^{-}{\pi }^{+})$. Dividing these product branching fractions by ${\bar{B}}^0\to {\bar{\Lambda }}_c^{-}{\Xi }_c^{+}$ yields: $\mathcal{B}({\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+})=[2.86\pm 1.21(stat.)\pm 0.38(syst.)]\%$ and $\mathcal{B}({\Xi }_c^{+}\to p{K}^{-}{\pi }^{+})=[0.45\pm 0.21(stat.)\pm 0.07(syst.)]\%$. Our result for $\mathcal{B}({\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+})$ can be combined with ${\Xi }_c^{+}$ branching fractions measured relative to ${\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}$ to set the absolute scale for many ${\Xi }_c^{+}$ branching fractions.

    ↳ hep-exhep-phPRD(2019)·57 citations
20. 20*

    Screened fifth forces in parity-breaking correlation functions

    Darsh Kodwani🇬🇧 · Harry Desmond🇬🇧

    Cross-correlating two different types of galaxy gives rise to parity breaking in the correlation function that derives from differences in the galaxies' properties and environments. This is typically associated with a difference in galaxy bias, describing the relation between galaxy number density and dark matter density, although observational effects such as magnification bias also play a role. In this paper we show that the presence of a screened fifth force adds additional degrees of freedom to the correlation function, describing the effective coupling of the force to the two galaxy populations. These are also properties of the galaxies' environments, but with different dependence in general to galaxy bias. We derive the parity-breaking correlation function analytically as a function of fifth-force strength and the two populations' fifth-force charges, and explore the result numerically using Hu-Sawicki $f(R)$ as a toy model of chameleon screening. We find that screening gives rise to an octopole, which, in the absence of magnification bias, is not present in any gravity theory without screening and thus is a qualitatively distinct signature. The modification to the dipole and octopole can be $\mathcal{O}(10\%)$ and $\mathcal{O}(100\%)$ respectively at redshift $z\gtrsim 0.5$ due to screening, but decreases towards lower redshift. The change in the background power spectrum in $f(R)$ theories induces a change in the dipole of roughly the same size, but dominant to the effect of screening at low $z$. While current data is insufficient to measure the parity-breaking dipole or octopole to the precision required to test these models, future surveys such as DESI, Euclid and SKA have the potential to probe screened fifth forces through the dipole.

    ↳ astro-ph.COastro-ph.GAgr-qchep-ph+1PRD(2019)·9 citations
21. 21*

    Bouncing Universe from Nothing

    Hiroki Matsui🇯🇵 · Fuminobu Takahashi🇯🇵 · Takahiro Terada🇯🇵

    We find a class of solutions for a homogeneous and isotropic universe in which the initially expanding universe stops expanding, experiences contraction, and then expands again (the "bounce"), in the framework of Einstein gravity with a real scalar field without violating the null energy condition nor encountering any singularities. Two essential ingredients for the bouncing universe are the positive spatial curvature and the scalar potential which becomes flatter at large field values. Depending on the initial condition, either the positive curvature or the negative potential stops the cosmic expansion and begins the contraction phase. The flat potential plays a crucial role in triggering the bounce. After the bounce, the flat potential naturally allows the universe to enter the slow-roll inflation regime, thereby making the bouncing universe compatible with observations. If the e-folding of the subsequent inflation is just enough, a positive spatial curvature may be found in the future observations. Our scenario nicely fits with the creation of the universe from nothing, which leads to the homogeneous and isotropic universe with positive curvature. As a variant of the mechanism, we also find solutions representing a cyclic universe.

    ↳ gr-qcastro-ph.COhep-phhep-thPLB(2019)·37 citations
22. 22*

    Pion generalized parton distribution from lattice QCD

    Jiunn-Wei Chen🇹🇼 · Huey-Wen Lin🇺🇸 · Jian-Hui Zhang🇩🇪

    We present the first lattice calculation of the valence-quark generalized parton distribution (GPD) of the pion using the large-momentum effective theory (LaMET) approach. We focus on the zero-skewness limit, where the GPD has a probability-density interpretation in the longitudinal Bjorken $x$ and the transverse impact-parameter distributions. Our calculation is done using clover valence fermions on an ensemble of gauge configurations with $2+1+1$ flavors (degenerate up/down, strange and charm) of highly improved staggered quarks (HISQ) with lattice spacing $a\approx 0.12$ fm, box size $L\approx 3$ fm and pion mass $m_{\pi }\approx 310$ MeV. The parton distribution function and the form factor are reproduced as special limits of the GPD as expected. Due to the large errors, this exploratory study does not show a clear preference among different model assumptions about the kinematic dependence of the GPD. To discriminate between these assumptions, future studies using higher-statistics data will be crucial.

    ↳ hep-lathep-phnucl-thNPB(2020)·127 citations
23. 23*

    Modified Friedmann equations via conformal Bohm -- De Broglie gravity

    G. Gregori🇬🇧 · B. Reville🇬🇧 · B. Larder🇬🇧

    We use an alternative interpretation of quantum mechanics, based on the Bohmian trajectory approach, and show that the quantum effects can be included in the classical equation of motion via a conformal transformation on the background metric. We apply this method to the Robertson-Walker metric to derive a modified version of Friedmann's equations for a Universe consisting of scalar, spin-zero, massive particles. These modified equations include additional terms that result from the non-local nature of matter and appear as an acceleration in the expansion of the Universe. We see that the same effect may also be present in the case of an inhomogeneous expansion.

    ↳ gr-qcastro-ph.COhep-phApJ(2019)·5 citations
24. 24*

    A survey of spectral models of gravity coupled to matter

    Ali H. Chamseddine🇳🇱 · Walter D. van Suijlekom🇳🇱

    This is a survey of the historical development of the Spectral Standard Model and beyond, starting with the ground breaking paper of Alain Connes in 1988 where he observed that there is a link between Higgs fields and finite noncommutative spaces. We present the important contributions that helped in the search and identification of the noncommutative space that characterizes the fine structure of space-time. The nature and properties of the noncommutative space are arrived at by independent routes and show the uniqueness of the Spectral Standard Model at low energies and the Pati-Salam unification model at high energies.

    ↳ hep-thhep-ph101 citations
25. 25*

    5d Dirac fermion on quantum graph

    Yukihiro Fujimoto🇯🇵 · Tomonori Inoue🇯🇵 · Makoto Sakamoto🇯🇵 · Kazunori Takenaga🇯🇵 · Inori Ueba🇯🇵

    In this paper, we investigate a five-dimensional Dirac fermion on a quantum graph that consists of a single vertex and $N$ loops. We find that the model possesses a rich structure of boundary conditions for wavefunctions on the quantum graph and they can be classified into $(2N+1)$ distinct categories. It is then shown that there appear degenerate four-dimensional chiral massless fermions in the four-dimensional mass spectrum. We briefly discuss how our model could naturally solve the problems of the fermion generation, the fermion mass hierarchy and the origin of the $CP$-violating phase.

    ↳ hep-thhep-phquant-phJ.Phys.A(2019)·5 citations
26. 26*

    Extracting the strangeness freeze-out temperature from net-Kaon data at RHIC

    Rene Bellwied🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Paolo Parotto🇺🇸 · Israel Portillo Vazquez🇺🇸 · Claudia Ratti🇺🇸 · Jamie Stafford🇺🇸

    Using the moments of the net-kaon distribution calculated within a state of-the-art hadron resonance gas model compared to experimental data from STAR's Beam Energy Scan, we find that the extracted strange freeze-out temperature is incompatible with the light one extracted from net-proton and net-charge fluctuations. Additionally predictions for net-$Lambda$ fluctuations are made that also appear to be consistent with a higher freeze-out temperature for strange particles. This strangeness freeze-out temperature is roughly $10-15$ MeV higher than the corresponding light freeze-out temperature. We also discuss cross-susceptibilities using different identified particles, which may be a further test of this two freeze-out temperature picture. Finally, we lay out the necessary updates needed in relativistic hydrodynamic models to take into account for this two freeze-out temperature scenario and present preliminary results of $\Lambda$ spectra at RHIC for AuAu $\sqrt{s_{NN}}=200$ GeV collisions that indicate a higher freeze-out temperature is preferred.

    ↳ nucl-thhep-phPoS(2019)·4 citations
27. 27*

    Conformal perturbation theory confronts lattice results in the vicinity of a critical point

    Michele Caselle🇮🇹 · Nicodemo Magnoli🇮🇹 · Alessandro Nada🇩🇪 · Marco Panero🇮🇹 · Marcello Scanavino🇮🇹

    We study the accuracy and predictive power of conformal perturbation theory by a comparison with lattice results in the neighborhood of the finite-temperature deconfinement transition of SU(2) Yang-Mills theory, assuming that the infrared properties of this non-Abelian gauge theory near criticality can be described by the Ising model. The results of this comparison show that conformal perturbation theory yields quantitatively accurate predictions in a broad temperature range. We discuss the implications of these findings for the description of the critical point (belonging to the same universality class) of another strongly coupled, non-supersymmetric non-Abelian gauge theory: the critical end-point in the phase diagram of QCD at finite temperature and finite quark chemical potential.

    ↳ hep-lathep-phhep-thnucl-thPRD(2019)·7 citations
28. 28*

    Soft Bootstrap and Effective Field Theories

    Ian Low🇺🇸 · Zhewei Yin🇺🇸

    The soft bootstrap program aims to construct consistent effective field theories (EFT's) by recursively imposing the desired soft limit on tree-level scattering amplitudes through on-shell recursion relations. A prime example is the leading two-derivative operator in the EFT of $\text{SU}(N)\times \text{SU}(N)/\text{SU}(N)$ nonlinear sigma model (NLSM), where $\mathcal{O}(p^2)$ amplitudes with an arbitrary multiplicity of external particles can be soft-bootstrapped. We extend the program to $\mathcal{O}(p^4)$ operators and introduce the "soft blocks," which are the seeds for soft bootstrap. The number of soft blocks coincides with the number of independent operators at a given order in the derivative expansion and the incalculable Wilson coefficient emerges naturally. We also uncover a new soft-constructible EFT involving the "multi-trace" operator at the leading two-derivative order, which is matched to $\text{SO}(N+1)/\text{SO}(N)$ NLSM. In addition, we consider Wess-Zumino-Witten (WZW) terms, the existence of which, or the lack thereof, depends on the number of flavors in the EFT, after a novel application of Bose symmetry. Remarkably, we find agreements with group-theoretic considerations on the existence of WZW terms in $\text{SU}(N)$ NLSM for $N\ge 3$ and the absence of WZW terms in $\text{SO}(N)$ NLSM for $N\ne 5$.

    ↳ hep-thhep-phnucl-thJHEP(2019)·65 citations
29. 29*

    Anthropic Bound on Dark Radiation and its Implications for Reheating

    Fuminobu Takahashi🇯🇵 · Masaki Yamada🇺🇸

    We derive an anthropic bound on the extra neutrino species, $\Delta N_{\mathrm{eff}}$, based on the observation that a positive $\Delta N_{\mathrm{eff}}$ suppresses the growth of matter fluctuations due to the prolonged radiation dominated era, which reduces the fraction of matter that collapses into galaxies, hence, the number of observers. We vary $\Delta N_{\mathrm{eff}}$ and the positive cosmological constant while fixing the other cosmological parameters. We then show that the probability of finding ourselves in a universe satisfying the current bound is of order a few percents for a flat prior distribution. If $\Delta N_{\mathrm{eff}}$ is found to be close to the current upper bound or the value suggested by the $H_0$ tension, the anthropic explanation is not very unlikely. On the other hand, if the upper bound on $\Delta N_{\mathrm{eff}}$ is significantly improved by future observations, such simple anthropic consideration does not explain the small value of $\Delta N_{\mathrm{eff}}$. We also study simple models where dark radiation consists of relativistic particles produced by heavy scalar decays, and show that the prior probability distribution sensitively depends on the number of the particle species.

    ↳ astro-ph.COhep-phhep-thJCAP(2019)·11 citations
30. 30*

    Superheavy Dark Matter and ANITA's Anomalous Events

    Dan Hooper🇺🇸 · Shalma Wegsman🇺🇸 · Cosmin Deaconu🇺🇸 · Abigail Vieregg🇺🇸

    The ANITA experiment, which is designed to detect ultra-high energy neutrinos, has reported the observation of two anomalous events, directed at angles of $27^{\circ }$ and $35^{\circ }$ with respect to the horizontal. At these angles, the Earth is expected to efficiently absorb ultra-high energy neutrinos, making the origin of these events unclear and motivating explanations involving physics beyond the Standard Model. In this study, we consider the possibility that ANITA's anomalous events are the result of Askaryan emission produced by exotic weakly interacting particles scattering elastically with nuclei in the Antarctic ice sheet. Such particles could be produced by superheavy ($\sim 10^{10}-10^{13}$ GeV) dark matter particles decaying in the halo of the Milky Way. Such scenarios can be constrained by existing measurements of the high-latitude gamma-ray background and the ultra-high energy cosmic ray spectrum, along with searches for ultra-high energy neutrinos by IceCube and other neutrino telescopes.

    ↳ astro-ph.HEastro-ph.COhep-phPRD(2019)·32 citations
31. 31*

    Gravitational Waves Induced by Scalar Perturbations during a Gradual Transition from an Early Matter Era to the Radiation Era

    Keisuke Inomata🇯🇵 · Kazunori Kohri🇯🇵 · Tomohiro Nakama🇨🇳 · Takahiro Terada🇯🇵

    We revisit the effects of an early matter-dominated era on gravitational waves induced by scalar perturbations. We carefully take into account the evolution of the gravitational potential, the source of these induced gravitational waves, during a gradual transition from an early matter-dominated era to the radiation-dominated era, where the transition timescale is comparable to the Hubble time at that time. Realizations of such a gradual transition include the standard perturbative reheating with a constant decay rate. Contrary to previous works, we find that the presence of an early matter-dominated era does not necessarily enhance the induced gravitational waves due to the decay of the gravitational potential around the transition from an early matter-dominated era to the radiation-dominated era.

    ↳ astro-ph.COgr-qchep-phJCAP(2019)·179 citations
32. 32*

    Enhancement of Gravitational Waves Induced by Scalar Perturbations due to a Sudden Transition from an Early Matter Era to the Radiation Era

    Keisuke Inomata🇯🇵 · Kazunori Kohri🇯🇵 · Tomohiro Nakama🇨🇳 · Takahiro Terada🇯🇵

    We study gravitational waves induced from the primordial scalar perturbations at second order around the reheating of the Universe. We consider reheating scenarios in which a transition from an early matter dominated era to the radiation dominated era completes within a timescale much shorter than the Hubble time at that time. We find that an enhanced production of induced gravitational waves occurs just after the reheating transition because of fast oscillations of scalar modes well inside the Hubble horizon. This enhancement mechanism just after an early matter-dominated era is much more efficient than a previously known enhancement mechanism during an early matter era, and we show that the induced gravitational waves could be detectable by future observations if the reheating temperature $T_{\text{R}}$ is in the range $T_{\text{R}}\lesssim 7\times 10^{-2}$GeV or $20\text{GeV}\lesssim T_{\text{R}}\lesssim 2\times 10^7\text{GeV}$. This is the case even if the scalar perturbations on small scales are not enhanced relative to those on large scales, probed by the observations of the cosmic microwave background.

    ↳ astro-ph.COgr-qchep-phPRD(2019)·225 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.