HEP Phenomenology·hep-ph

Tue·Oct 3, 2017Tuesday·October 3, 2017

36 papers—25 primary·11 cross-listed·reconstructed*

01*
Factorization and Resummation for Groomed Multi-Prong Jet Shapes
Andrew J. Larkoski🇺🇸 · Ian Moult🇺🇸 · Duff Neill🇺🇸
Observables which distinguish boosted topologies from QCD jets are playing an increasingly important role at the Large Hadron Collider (LHC). These observables are often used in conjunction with jet grooming algorithms, which reduce contamination from both theoretical and experimental sources. In this paper we derive factorization formulae for groomed multi-prong substructure observables, focusing in particular on the groomed $D_{2}$ observable, which is used to identify boosted hadronic decays of electroweak bosons at the LHC. Our factorization formulae allow systematically improvable calculations of the perturbative $D_{2}$ distribution and the resummation of logarithmically enhanced terms in all regions of phase space using renormalization group evolution. They include a novel factorization for the production of a soft subjet in the presence of a grooming algorithm, in which clustering effects enter directly into the hard matching. We use these factorization formulae to draw robust conclusions of experimental relevance regarding the universality of the $D_{2}$ distribution in both $e^{+} e^{-}$ and $pp$ collisions. In particular, we show that the only process dependence is carried by the relative quark vs. gluon jet fraction in the sample, no non-global logarithms from event-wide correlations are present in the distribution, hadronization corrections are controlled by the perturbative mass of the jet, and all global color correlations are completely removed by grooming, making groomed $D_{2}$ a theoretically clean QCD observable even in the LHC environment. We compute all ingredients to one-loop accuracy, and present numerical results at next-to-leading logarithmic accuracy for $e^{+} e^{-}$ collisions, comparing with parton shower Monte Carlo simulations. Results for $pp$ collisions, as relevant for phenomenology at the LHC, are presented in a companion paper.
hep-phhep-exnucl-thJHEP(2018)·50 citations
02*
A fast and accurate method for perturbative resummation of transverse momentum-dependent observables
Daekyoung Kang🇨🇳 · Christopher Lee🇺🇸 · Varun Vaidya🇺🇸
We propose a novel strategy for the perturbative resummation of transverse momentum-dependent (TMD) observables, using the $q_{T}$ spectra of gauge bosons ( $γ^{*}$ , Higgs) in $pp$ collisions in the regime of low (but perturbative) transverse momentum $q_{T}$ as a specific example. First we introduce a scheme to choose the factorization scale for virtuality in momentum space instead of in impact parameter space, allowing us to avoid integrating over (or cutting off) a Landau pole in the inverse Fourier transform of the latter to the former. The factorization scale for rapidity is still chosen as a function of impact parameter $b$ , but in such a way designed to obtain a Gaussian form (in $ln b$ ) for the exponentiated rapidity evolution kernel, guaranteeing convergence of the $b$ integral. We then apply this scheme to obtain the $q_{T}$ spectra for Drell-Yan and Higgs production at NNLL accuracy. In addition, using this scheme we are able to obtain a fast semi-analytic formula for the perturbative resummed cross sections in momentum space: analytic in its dependence on all physical variables at each order of logarithmic accuracy, up to a numerical expansion for the pure mathematical Bessel function in the inverse Fourier transform that needs to be performed just once for all observables and kinematics, to any desired accuracy.
hep-phnucl-thJHEP(2018)·26 citations
03*
Lepton flavor violating meson decays
Derek E. Hazard🇺🇸
We argue that lepton flavor violating (LFV) decays $M \to ℓ_{1} ℓ_{2}$ of meson states $M$ with different quantum numbers could be used to put constraints on the Wilson coefficients of effective operators describing LFV interactions at low energy scales. We note that the restricted kinematics of the two-body decay of quarkonium or a heavy quark meson allows us to select operators with particular quantum numbers, significantly reducing the reliance on the $s in g l e o p er a t or d o minan ce$ assumption that is prevalent in constraining parameters of the effective LFV Lagrangian. We shall also argue that studies of radiative lepton flavor violating $M \to γ ℓ_{1} ℓ_{2}$ decays could provide important complementary access to those effective operators.
hep-phhep-ex1 citation
04*
Higgs production at future $e^{+} e^{-}$ colliders in the Georgi-Machacek model
Bin Li🇨🇳 · Zhi-Long Han🇨🇳 · Yi Liao🇨🇳
We study how the dominant single and double SM-like Higgs ( $h$ ) production at future $e^{+} e^{-}$ colliders is modified in the Georgi-Machacek (GM) model. On imposing theoretical, indirect and direct constraints, significant deviations of $h$ -couplings from their SM values are still possible; for instance, the Higgs-gauge coupling coupling can be corrected by a factor $κ_{hV V} \in [0.93, 1.15]$ in the allowed parameter space. For the Higgs-strahlung $e^{+} e^{-} \to h Z$ and vector boson fusion processes $e^{+} e^{-} \to h ν ν ˉ, h e^{+} e^{-}$ , the cross section could increase by $32%$ or decrease by $13%$ . In the case of associated production with a top quark pair $e^{+} e^{-} \to h t t ˉ$ , the cross section can be enhanced up to several times when the custodial triplet scalar $H_{3}^{0}$ is resonantly produced. In the meanwhile, the double Higgs production $e^{+} e^{-} \to hh Z (hh ν ν ˉ)$ can be maximally enhanced by one order of magnitude at the resonant $H_{1, 3}^{0}$ production. We also include exclusion limits expected from future LHC runs at higher energy and luminosity and discuss their further constraints on the relevant model parameters. We find that the GM model can result in likely measurable deviations of Higgs production from the SM at future $e^{+} e^{-}$ colliders.
hep-phJHEP(2018)·19 citations
05*
QCD coupling which respects lattice restrictions at low energies
Cesar Ayala🇨🇱
We consider a phenomenologycal parametrization of the QCD running coupling which arises from the dispersion relation respecting the holomorphic properties of the physical QCD observables in the complex momentum plane. The parameters are fixed by the following requirements: 1) at enough high energies, it reproduces the underlying perturbative coupling, 2) at intermediate energy momenta, it reproduces the experimental semihadronic tau decay ratio, and 3) in the deep IR regime, it satisfies the qualitative properties coming from recent lattice results. Finally, we apply this new coupling to low-energy available experimental data. In particular, to Borel sum rules for {\tau}-decay, extracting the values of the dimension 4 and 6 condensates, to the V-channel Adler function, and to polarized Bjorken Sum Rule.
hep-phNucl.Part.Phys.Proc.(2018)·3 citations
06*
Search for Massive Bosons Decaying to Wg and Zg Using the ATLAS Detector
Wei Tang🇺🇸
The Standard Model is by far the most encompassing physics theory. With the recent discovery of the Higgs Boson, the Standard Model has performed extremely well against experimental data. However, the theory is intrinsically not complete, it does not address physical phenomenon such as gravity and dark matter. Many proposals for physics beyond the Standard Model predict new massive bosons from additional gauge fields or extended Higgs sectors. This paper examines a preliminary search of possible V gamma decay channels of proposed new bosons.
hep-ph0 citations
07*
Strongly self-interacting vector dark matter via freeze-in
Mateusz Duch🇵🇱 · Bohdan Grzadkowski🇵🇱 · Da Huang🇵🇱
We study a vector dark matter (VDM) model in which the dark sector couples to the Standard Model sector via a Higgs portal. If the portal coupling is small enough the VDM can be produced via the freeze-in mechanism. It turns out that the electroweak phase transition have a substantial impact on the prediction of the VDM relic density. We further assume that the dark Higgs boson which gives the VDM mass is so light that it can induce strong VDM self-interactions and solve the small-scale structure problems of the Universe. As illustrated by the latest LUX data, the extreme smallness of the Higgs portal coupling required by the freeze-in mechanism implies that the dark matter direct detection bounds are easily satisfied. However, the model is well constrained by the indirect detections of VDM from BBN, CMB, AMS-02, and diffuse $γ$ /X-rays. Consequently, only when the dark Higgs boson mass is at most of $O (keV)$ does there exist a parameter region which leads to a right amount of VDM relic abundance and an appropriate VDM self-scattering while satisfying all other constraints simultaneously.
hep-phastro-ph.COJHEP(2018)·50 citations
08*
Quasi-two-body decays $B_{c} \to D_{(s)} [ρ (770), ρ (1450), ρ (1700) \to] π π$ in the perturbative QCD factorization approach
Ai-Jun Ma🇨🇳 · Ya Li🇨🇳 · Zhen-Jun Xiao🇨🇳
In this paper, we studied the quasi-two-body $B_{c} \to D_{(s)} [ρ (770), ρ (1450), ρ (1700) \to] π π$ decays by employing the perturbative QCD (PQCD) factorization approach. The two-pion distribution amplitudes $Φ_{π π}$ are applied to include the final-state interactions between the pion pair, while the time-like form factors $F_{π} (w^{2})$ associated with the $P$ -wave resonant states $ρ (770)$ , $ρ (1450)$ and $ρ (1700)$ are extracted from the experimental data of the $e^{+} e^{-}$ annihilation. We found that: (a) the PQCD predictions for the branching ratios of the quasi-two-body $B_{c} \to D_{(s)} [ρ (770), ρ (1450), ρ (1700) \to] π π$ decays are in the order of $1 0^{- 9}$ to $1 0^{- 5}$ and the direct $C P$ violations around $(10 - 40) %$ in magnitude; (b) the two sets of the large hierarchy $R_{1 a, 1 b, 1 c}$ and $R_{2 a, 2 b, 2 c}$ for the ratios of the branching ratios of the considered decays are defined and can be understood in the PQCD factorization approach, while the self-consistency between the quasi-two-body and two-body framework for $B_{c} \to D_{(s)} [ρ (770) \to] π π$ and $B_{c} \to D_{(s)} ρ (770)$ decays are confirmed by our numerical results; (c) taking currently known $B (ρ (1450) \to π π)$ and $B (ρ (1700) \to π π)$ as input, we extracted the theoretical predictions for $B (B_{c} \to D ρ (1450))$ and $B (B_{c} \to D ρ (1700))$ from the PQCD predictions for the decay rates of the quasi-two-body decays $B_{c} \to D [ρ (1450), ρ (1700) \to] π π$ . All the PQCD predictions will be tested in the future experiments.
hep-phNPB(2018)·12 citations
09*
Exploring $R_{D}$ , $R_{D^{*}}$ and $R_{J /Ψ}$ anomalies
Rupak Dutta🇮🇳
Deviations from the standard model predictions have been reported in various observables concerned with the lepton flavor universality. At present, the deviation of the measured values of $R_{D}$ and $R_{D^{*}}$ from the standard model expectation is exceeded by $2.3 σ$ and $3.4 σ$ , respectively. Very recently LHCb has measured the ratio of branching ratio $R_{J /Ψ} = B (B_{c} \to J /Ψ τ ν) / B (B_{c} \to J /Ψ l ν)$ , where $l \in (e, μ)$ , to be $0.71 \pm 0.17 \pm 0.18$ which is at more than $2 σ$ away from the standard model prediction. We investigate the anomalies in $R_{D}$ , $R_{D^{*}}$ , and $R_{J /Ψ}$ using a model independent framework with minimal number of new physics couplings. We find various new physics models that can explain these anomalies within $1 σ$ .
hep-ph41 citations
10*
Some Dipole Shower Studies
Baptiste Cabouat (The University of Manchester)🇸🇪 · Torbjörn Sjöstrand (Lund University)🇸🇪
Parton showers have become a standard component in the description of high-energy collisions. Nowadays most final-state ones are of the dipole character, wherein a pair of partons branches into three, with energy and momentum preserved inside this subsystem. For initial-state showers a dipole picture is also possible and commonly used, but the older global-recoil strategy remains a valid alternative, wherein larger groups of partons share the energy--momentum preservation task. In this article we introduce and implement a dipole picture also for initial-state radiation in PYTHIA, and compare with the existing global-recoil one, and with data. For the case of Deeply Inelastic Scattering we can directly compare with matrix element expressions and show that the dipole picture gives a very good description over the whole phase space, at least for the first branching.
hep-phEPJC(2018)·104 citations
11*
CP violation in $D^{0} \to K^{+} π^{-}$
David Delepine🇲🇽 · Gaber Faisel🇹🇷 · Carlos A. Ramirez🇨🇴
In this paper we study the direct CP asymmetry of the doubly Cabibbo-suppressed decay mode $D^{0} \to K^{+} π^{-}$ within standard model and two Higgs doublet model with generic Yukawa structure. In the standard model we derive the corrections to the tree level amplitude, generated from the box and di-penguin diagrams, required for generating the weak CP violating phases. We show that these phases are so tiny leading to a direct CP asymmetry of order $1 0^{- 9}$ . Regarding the two Higgs doublet model with generic Yukawa structure we derive the Wilson coefficients relevant to $D^{0} \to K^{+} π^{-}$ . After taking into account all constraints on the parameter space of the model we show that charged Higgs couplings to quarks can lead to a direct CP asymmetry of order $1 0^{- 3}$ which is $6$ orders of magnitude larger than the standard model prediction.
hep-phhep-exPRD(2017)·3 citations
12*
The Thomas-Fermi quark model and mesonic matter
Suman Baral🇺🇸 · Walter Wilcox🇺🇸
The first results of a new application of the Thomas-Fermi statistical quark model to mesonic matter is presented. Interesting aspects of the theory are discussed, distinguishing such states from baryonic matter. A major motivation of this study is the tetraquark states discovered by the Belle and other collaborations and the possibility that stable multi-quark families of such states exist. Similar to our previous baryonic study, we use a two-inequivalent wave function approach to investigate aspects of multi-quark matter. We think of our model as a tool for quickly assessing the characteristics of new, possibly bound, particle states of higher quark number content, which can not yet be examined by lattice methods.
hep-phhep-lat4 citations
13*
Cumulant Expansion in Gluon Saturation, and Five and Six-Gluon Azimuthal Correlations
Sener Ozonder🇹🇷
Correlations between the momenta of the final state hadrons measured in proton or nucleus collisions contain information that sheds light on the initial conditions and evolutionary dynamics of the collision system. These correlation measurements have revealed the long-range rapidity correlations in p-p and p-Pb systems, and they have also made it possible to extract the elliptic flow coefficient from hadron correlation measurements. In this work, we calculate five- and six-gluon correlation functions in the framework of saturation physics by using superdiagrams. We also derive the cumulant expansion of the gluon correlators that is valid in the gluon saturation limit. We show that the cumulant expansion of the gluon correlators that is used for counting the number of diagrams to be calculated does not follow the standard cumulant expansion. We also explain how these findings can be used in obtaining experimentally relevant observables such as flow coefficients calculated from correlations as well as ratios of the correlation functions of different orders.
hep-phhep-thnucl-thPRD(2017)·3 citations
14*
Moving heavy quarkonium entropy, effective string tension, and the QCD phase diagram
Xun Chen🇨🇳 · Sheng-Qin Feng🇨🇳 · Ya-Fei Shi🇨🇳 · Yang Zhong🇨🇳
The entropy and effective string tension of the moving heavy quark-antiquark pair in the strongly coupled plasmas are calculated by using a deformed an anti-de Sitter/Reissner-Nordstr $o ¨$ m black hole metric. A sharp peak of the heavy-quarkonium entropy around the deconfinement transition can be realized in our model, which is consistent with the lattice QCD result. The effective string tension of the heavy quark-antiquark pair is related to the deconfinement phase transition. Thus, we investigate the deconfinement phase transition by analyzing the characteristics of the effective string tension with different temperatures, chemical potentials, and rapidities. It is found that the results of phase diagram calculated through effective string tension are in agreement with results calculated through a Polyakov loop. We argue that a moving system will reach the phase transition point at a lower temperature and chemical potential than a stationary system. It means that the lifetime of the moving QGP becomes longer than the static one.
hep-phPRD(2018)·47 citations
15*
A non-vanishing neutrino mass and the strong CP problem: A new solution from the perspective of the EW- $ν_{R}$ model
P. Q. Hung🇺🇸
The EW- $ν_{R}$ model was constructed to provide a scenario in which right-handed neutrinos are non-sterile and have masses proportional to the electroweak scale, providing an opportunity to test the seesaw mechanism at the LHC. What was hidden in the model until recently is the chiral symmetry which helps solve the strong CP problem by using it to rotate $θ_{QC D}$ to zero. It turns out the contribution from the electroweak sector to the effective $θ ˉ$ is proportional to the light neutrino masses and is naturally small, satisfying the constraint coming from the present absence of the neutron electric dipole moment, and without the need for an axion. Talk presented at the APS Division of Particles and Fields Meeting (DPF 2017), July 31-August 4, 2017, Fermilab. C170731
hep-ph4 citations
16*
Elliptic flow coefficients from transverse momentum conservation
Adam Bzdak🇵🇱 · Guo-Liang Ma🇨🇳
We calculate the $k$ -particle ( $k = 2, 4, 6, 8$ ) azimuthal cumulants resulting from the conservation of transverse momentum. We find that $c_{2} {k} > 0$ and depending on the transverse momenta, $c_{2} {k}$ can reach substantial values even for a relatively large number of particles. The impact of our results on the understanding of the onset of collectivity in small systems is emphasized.
hep-phhep-exnucl-exnucl-thPRC(2018)·11 citations
17*
Baryon-antibaryon annihilation and reproduction in relativistic heavy-ion collisions
E. Seifert🇩🇪 · W. Cassing🇩🇪
The quark rearrangement model for baryon-antibaryon annihilation and reproduction ( $B B ˉ \leftrightarrow 3 M$ ) - incorporated in the Parton-Hadron-String Dynamics (PHSD) transport approach - is extended to the strangeness sector. A derivation of the transition probabilities for the three-body processes is presented and a strangeness suppression factor for the invariant matrix element squared is introduced to account for the higher mass of the strange quark compared to the light up and down quarks. In simulations of the baryon-antibaryon annihilation and reformation in a box with periodic boundary conditions we demonstrate that our numerical implementation fulfills detailed balance on a channel-by-channel basis for more than 2000 individual $2 \leftrightarrow 3$ channels. Furthermore, we study central Pb+Pb collisions within PHSD from 11.7 $A$ GeV to 158 $A$ GeV and investigate the impact of the additionally implemented reaction channels in the strangeness sector. We find that the new reaction channels have a visible impact essentially only on the rapidity spectra of antibaryons. The spectra with the additional channels in the strangeness sector are closer to the experimental data than without for all antihyperons. Due to the chemical redistribution between baryons/antibaryons and mesons we find a slightly larger production of antiprotons thus moderately overestimating the available experimental data. We additionally address the question if the antibaryon spectra (with strangeness) from central heavy-ion reactions at these energies provide further information on the issue of chiral symmetry restoration and deconfinement. However, by comparing transport results with/without partonic phase as well as including/excluding effects from chiral symmetry restoration we find no convincing signals in the strange antibaryon sector for either transition due to the strong final-state interactions.
hep-phnucl-thPRC(2018)·28 citations
18*
Effect of the $K K$ and $η η$ channels and interference phenomena in the two-pion and $K K$ transitions of charmonia and bottomonia
Yury S. Surovtsev🇷🇺 · Petr Bydžovský🇨🇿 · Thomas Gutsche🇩🇪 · Robert Kamiński🇵🇱 · Valery E. Lyubovitskij🇩🇪 · Miroslav Nagy🇸🇰
It is shown that the basic shape of dipion and $K K$ mass spectra in decays $J / ψ \to ϕ (π π, K K)$ , $ψ (2 S) \to J / ψ π π$ , $Y (4260) \to J / ϕ π π$ and in the two-pion transitions of bottomonia states are explained by an unified mechanism based on the contribution of the $π π$ , $K K$ and $η η$ coupled channels including their interference. The role of the individual $f_{0}$ resonances in making up the shape of the dipion mass distributions in the charmonia and bottomonia decays is considered.
hep-phPRD(2018)·3 citations
19*
Higgs-Cosmology Interplay
Oleg Lebedev🇫🇮
I discuss the role of the Higgs boson as a probe of dark matter and inflation.
hep-phastro-ph.COPoS(2017)·1 citation
20*
Angular distribution of polarised $Λ_{b}$ baryons decaying to $Λ ℓ^{+} ℓ^{-}$
Thomas Blake🇬🇧 · Michal Kreps🇬🇧
Rare $b \to s ℓ^{+} ℓ^{-}$ flavour-changing-neutral-current processes provide important tests of the Standard Model of particle physics. Angular observables in exclusive $b \to s ℓ^{+} ℓ^{-}$ processes can be particularly powerful as they allow hadronic uncertainties to be controlled. Amongst the exclusive processes that have been studied by experiments, the decay $Λ_{b} \to Λ ℓ^{+} ℓ^{-}$ is unique in that the $Λ_{b}$ baryon can be produced polarised. In this paper, we derive an expression for the angular distribution of the $Λ_{b} \to Λ ℓ^{+} ℓ^{-}$ decay for the case where the $Λ_{b}$ baryon is produced polarised. This extends the number of angular observables in this decay from 10 to 34. Standard Model expectations for the new observables are provided and the sensitivity of the observables is explored under a variety of new physics models. At low-hadronic recoil, four of the new observables have a new short distance dependence that is absent in the unpolarised case. The remaining observables depend on the same short distance contributions as the unpolarised observables, but with different dependence on hadronic form-factors. These relations provide possibilities for novel tests of the SM that could be carried out with the data that will become available at the LHC or a future $e^{+} e^{-}$ collider.
hep-phJHEP(2017)·65 citations
21*
Cross-sections for $ν_{μ}$ and $ν_{μ} ˉ$ induced single pion production processes in the few GeV using NuWro
Qudsia Gani🇮🇳 · W. Bari🇮🇳
For a continued progress in the pursuit of neutrino oscillation parameters, we require to have a precise knowledge of the pion production processes which act as a source of backgrounds and systematic uncertainties in neutrino oscillation experiments because pions can mimic a final state electron (positron). Therefore a pion production principal interaction may appear to be quasi-elastic if the pion is absorbed in the final state interactions. Charged-current single pion production processes induced by $ν_{μ}$ and $ν_{μ} ˉ$ interactions with hydrocarbon target $(C H_{2})$ has been studied using NuWro event generator and the cross-sections so obtained have been compared with the results of Miner $ν$ A experiment.
hep-ph1 citation
22*
New test of Lorentz symmetry using ultrahigh-energy cosmic rays
Luis A. Anchordoqui🇺🇸 · Jorge F. Soriano🇺🇸
We propose an innovative test of Lorentz symmetry by observing pairs of simultaneous parallel extensive air showers produced by the fragments of ultrahigh-energy cosmic ray nuclei which disintegrated in collisions with solar photons. We show that the search for a cross-correlation of showers in arrival time and direction becomes background free for an angular scale < 3^\circ and a time window {\cal O}(10 s). We also show that if the solar photo-disintegration probability of helium is {\cal O} (10^{-5.5}) then the hunt for spatiotemporal coincident showers could be within range of existing cosmic ray facilities, such as the Pierre Auger Observatory. We demonstrate that the actual observation of a few events can be used to constrain Lorentz violating dispersion relations of the nucleon.
hep-phastro-ph.HEPRD(2018)·8 citations
23*
Dark Revelations of the $[S U (3)]^{3}$ and $[S U (3)]^{4}$ Gauge Extensions of the Standard Model
Corey Kownacki🇺🇸 · Ernest Ma🇺🇸 · Nicholas Pollard🇺🇸 · Oleg Popov🇺🇸 · Mohammadreza Zakeri🇺🇸
Two theoretically well-motivated gauge extensions of the standard model are $S U (3)_{C} \times S U (3)_{L} \times S U (3)_{R}$ and $S U (3)_{q} \times S U (3)_{L} \times S U (3)_{l} \times S U (3)_{R}$ , where $S U (3)_{q}$ is the same as $S U (3)_{C}$ and $S U (3)_{l}$ is its color leptonic counterpart. Each as three variations, according to how $S U (3)_{R}$ is broken. It is shown here for the first time that a built-in dark $U (1)_{D}$ gauge symmetry exists in all six versions, and may be broken to discrete $Z_{2}$ dark parity. The available dark matter candidates in each case include fermions, scalars, as well as {\it vector gauge bosons}. This work points to the unity of matter with dark matter, the origin of which is not {\it ad hoc}.
hep-phPLB(2018)·18 citations
24*
Radiative resonance couplings in $γ π \to π π$
Martin Hoferichter🇺🇸 · Bastian Kubis🇩🇪 · Marvin Zanke🇩🇪
Studies of the reaction $γ π \to π π$ , in the context of the ongoing Primakoff program of the COMPASS experiment at CERN, give access to the radiative couplings of the $ρ (770)$ and $ρ_{3} (1690)$ resonances. We provide a vector-meson-dominance estimate of the respective radiative width of the $ρ_{3}$ , $Γ_{ρ_{3} \to π γ} = 48 (18)$ keV, as well as its impact on the $F$ -wave in $γ π \to π π$ . For the $ρ (770)$ , we establish the formalism necessary to extract its radiative coupling directly from the residue of the resonance pole by analytic continuation of the $γ π \to π π$ amplitude to the second Riemann sheet, without any reference to the vector-meson-dominance hypothesis.
hep-phhep-exnucl-thPRD(2017)·81 citations
25*
Classicality and Quantum Break-Time for Cosmic Axions
Gia Dvali🇩🇪 · Sebastian Zell🇩🇪
We investigate the length of the period of validity of a classical description for the cosmic axion field. To this end, we first show that we can understand the oscillating axion solution as expectation value over an underlying coherent quantum state. Once we include self-interaction of the axion, the quantum state evolves so that the expectation value over it starts to deviate from the classical solution. The time-scale of this process defines the quantum break-time. For the hypothetical dark matter axion field in our Universe, we show that quantum break-time exceeds the age of the Universe by many orders of magnitude. This conclusion is independent of specific properties of the axion model. Thus, experimental searches based on the classical approximation of the oscillating cosmic axion field are fully justified. Additionally, we point out that the distinction of classical nonlinearities and true quantum effects is crucial for calculating the quantum break-time in any system. Our analysis can also be applied to other types of dark matter that are described as classical fluids in the mean field approximation.
hep-phastro-ph.COhep-thJCAP(2018)·65 citations
26*
Revealing Fine Structure in the Antineutrino Spectra From a Nuclear Reactor
A. A. Sonzogni🇺🇸 · M. Nino🇺🇸 · E. A. McCutchan🇺🇸
We calculate the Inverse Beta Decay (IBD) antineutrino spectrum generated by nuclear reactors using the summation method to understand deviations from the smooth Huber-Mueller model due to the decay of individual fission products, showing that plotting the ratio of two adjacent spectra points can effectively reveal these deviations. We obtained that for binning energies of 0.1 MeV or lower, abrupt changes in the spectra due to the jagged nature of the individual antineutrino spectra could be observed for highly precise experiments. Surprisingly, our calculations also reveal a peak-like feature in the adjacent points ratio plot at 4.5 MeV even with a 0.25 MeV binning interval, which we find is present in the IBD Daya Bay spectrum published in 2016. We show that this 4.5 MeV feature is caused by the contributions of just four fission products, 95Y, 98,101N and 102Tc. This would be the first evidence of the decay of a few fission products in the IBD antineutrino spectrum from a nuclear reactor.
↳ nucl-thhep-exhep-phnucl-exPRC(2018)·40 citations
27*
$β_{I R}^{'}$ at an Infrared Fixed Point in Chiral Gauge Theories
Thomas A. Ryttov🇩🇰 · Robert Shrock🇺🇸
We present scheme-independent calculations of the derivative of the beta function, denoted $β_{I R}^{'}$ , at a conformally invariant infrared (IR) fixed point, in several asymptotically free chiral gauge theories, namely SO( $4 k + 2$ ) with $2 \leq k \leq 4$ with respective numbers $N_{f}$ of fermions in the spinor representation, and E $_{6}$ with fermions in the fundamental representation.
↳ hep-thhep-phPRD(2018)·8 citations
28*
Studies of quarkonium at Belle and Belle II
Bryan Fulsom🇺🇸
Quarkonium is the bound state of a heavy quark and its anti-quark counterpart. The study of this system has experienced a renaissance thanks to results from e+e- collider experiments, including discoveries of long-predicted conventional quarkonia, and unusual states consisting of four quarks. The Belle Experiment operated at KEK in Japan from 1999-2010. Analysis of the collected data continues to produce new findings. The Belle II experiment is a substantial upgrade of both the Belle detector and the KEKB accelerator, aiming to collect 50 times more data beginning in 2018. This talk presented recent Belle results related to hadronic and radiative decays in the bottomonium system. It described the capabilities of Belle II to explore these topics, with a particular focus on the physics reach of the first data, where unique opportunities exist to make an immediate impact in this area.
↳ hep-exhep-ph3 citations
29*
Hot Spaghetti: Viscous Gravitational Collapse
Berndt Müller🇺🇸 · Andreas Schäfer🇩🇪
We explore the fate of matter falling into a macroscopic Schwarzschild black hole for the simplified case of a radially collapsing thin spherical shell for which the back reaction of the geometry can be neglected. We treat the internal dynamics of the infalling matter in the framework of viscous relativistic hydrodynamics and calculate how the internal temperature of the collapsing matter evolves as it falls toward the Schwarzschild singularity. We find that viscous hydrodynamics fails when either, the dissipative radial pressure exceeds the thermal pressure and the total radial pressure becomes negative, or the time scale of variation of the tidal forces acting on the collapsing matter becomes shorter than the characteristic hydrodynamic response time.
↳ gr-qchep-phnucl-thEPJA(2018)·0 citations
30*
Understanding caustic crossings in giant arcs: characteristic scales, event rates, and constraints on compact dark matter
Masamune Oguri🇯🇵 · Jose M. Diego🇪🇸 · Nick Kaiser🇨🇦 · Patrick L. Kelly🇺🇸 · Tom Broadhurst🇪🇸
The recent discovery of fast transient events near critical curves of massive galaxy clusters, which are interpreted as highly magnified individual stars in giant arcs due to caustic crossing, opens up the possibility of using such microlensing events to constrain a range of dark matter models such as primordial black holes and scalar field dark matter. Based on a simple analytic model, we study lensing properties of a point mass lens embedded in a high magnification region, and derive the dependence of the peak brightness, microlensing time scales, and event rates on the mass of the point mass lens as well as the radius of a source star that is magnified. We find that the lens mass and source radius of the first event MACS J1149 Lensed Star 1 (LS1) are constrained, with the lens mass range of $0.1 M_{⊙} ≲ M ≲ 4 \times 1 0^{3} M_{⊙}$ and the source radius range of $40 R_{⊙} ≲ R ≲ 260 R_{⊙}$ . In the most plausible case with $M \approx 0.3 M_{⊙}$ and $R \approx 180 R_{⊙}$ , the source star should have been magnified by a factor of $\approx 4300$ at the peak. The derived lens properties are fully consistent with the interpretation that MACS J1149 LS1 is a microlensing event produced by a star that contributes to the intra-cluster light. We argue that compact dark matter models with high fractional mass densities for the mass range $1 0^{- 5} M_{⊙} ≲ M ≲ 1 0^{2} M_{⊙}$ are inconsistent with the observation of MACS J1149 LS1 because such models predict too low magnifications. Our work demonstrates a potential use of caustic crossing events in giant arcs to constrain compact dark matter.
↳ astro-ph.COhep-phPRD(2018)·248 citations
31*
Cosmological imprints of string axions in plateau
Jiro Soda🇯🇵 · Yuko Urakawa🇯🇵
We initiate a study on various cosmological imprints of string axions whose scalar potentials have plateau regions. In such cases, we show that a delayed onset of oscillation generically leads to a parametric resonance instability. In particular, for ultralight axions, the parametric resonance can enhance the power spectrum slightly below the Jeans scale, alleviating the tension with the Lyman $α$ forest observations. We also argue that a long-lasting resonance can lead to an emission of gravitational waves at the frequency bands which are detectable by gravitational wave interferometers and pulsar timing arrays.
↳ astro-ph.COgr-qchep-phhep-thEPJC(2018)·34 citations
32*
Baryons in the plasma: in-medium effects and parity doubling
Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Davide de Boni🇬🇧 · Simon Hands🇬🇧 · Benjamin Jäger🇨🇭 · Chrisanthi Praki🇬🇧 · Jon-Ivar Skullerud🇮🇪
We investigate the fate of baryons made out of u, d and s quarks in the hadronic gas and the quark-gluon plasma, using nonperturbative lattice simulations, employing the FASTSUM anisotropic Nf=2+1 ensembles. In the confined phase a strong temperature dependence is seen in the masses of the negative-parity groundstates, while the positive-parity groundstate masses are approximately temperature independent, within the error. At high temperature parity doubling emerges. A noticeable effect of the heavier s quark is seen. We give a simple description of the medium-dependent masses for the negative-parity states and speculate on the relevance for heavy-ion phenomenology via the hadron resonance gas.
↳ hep-lathep-phnucl-thEPJ Web Conf.(2018)·16 citations
33*
Neutrino oscillations: the rise of the PMNS paradigm
Claudio Giganti🇫🇷 · Stéphane Lavignac🇫🇷 · Marco Zito🇫🇷
Since the discovery of neutrino oscillations, the experimental progress in the last two decades has been very fast, with the precision measurements of the neutrino squared-mass differences and of the mixing angles, including the last unknown mixing angle $θ_{13}$ . Today a very large set of oscillation results obtained with a variety of experimental configurations and techniques can be interpreted in the framework of three active massive neutrinos, whose mass and flavour eigenstates are related by a 3 $\times$ 3 unitary mixing matrix, the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix, parameterized by three mixing angles $θ_{12}$ , $θ_{23}$ , $θ_{13}$ and a CP-violating phase $δ_{C P}$ . The additional parameters governing neutrino oscillations are the squared-mass differences $Δ m_{j i}^{2} = m_{j}^{2} - m_{i}^{2}$ , where $m_{i}$ is the mass of the $i$ th neutrino mass eigenstate. This review covers the rise of the PMNS three-neutrino mixing paradigm and the current status of the experimental determination of its parameters. The next years will continue to see a rich program of experimental endeavour coming to fruition and addressing the three missing pieces of the puzzle, namely the determination of the octant and precise value of the mixing angle $θ_{23}$ , the unveiling of the neutrino mass ordering (whether $m_{1} < m_{2} < m_{3}$ or $m_{3} < m_{1} < m_{2}$ ) and the measurement of the CP-violating phase \dcp.
↳ hep-exhep-phPPNP(2018)·201 citations
34*
Excited cosmic strings with superconducting currents
Betti Hartmann🇧🇷 · Florent Michel🇬🇧 · Patrick Peter🇫🇷
We present a detailed analysis of {\it excited} cosmic string solutions which possess superconducting currents. These currents can be excited inside the string core, and - if the condensate is large enough - can lead to the excitations of the Higgs field. Next to the case with global unbroken symmetry, we discuss also the effects of the gauging of this symmetry and show that excited condensates persist when coupled to an electromagnetic field. The space-time of such strings is also constructed by solving the Einstein equations numerically and we show how the local scalar curvature is modified by the excitation. We consider the relevance of our results on the cosmic string network evolution as well as observations of primordial gravitational waves and cosmic rays.
↳ hep-thgr-qchep-phPRD(2017)·12 citations
35*
Spectroscopy of SU(4) composite Higgs theory with two distinct fermion representations
Venkitesh Ayyar🇺🇸 · Thomas DeGrand🇺🇸 · Maarten Golterman🇺🇸 · Daniel C. Hackett🇺🇸 · William I. Jay🇺🇸 · Ethan T. Neil🇺🇸 · Yigal Shamir🇮🇱 · Benjamin Svetitsky🇮🇱
We have simulated the SU(4) lattice gauge theory coupled to dynamical fermions in the fundamental and two-index antisymmetric (sextet) representations simultaneously. Such theories arise naturally in the context of composite Higgs models that include a partially composite top quark. We describe the low-lying meson spectrum of the theory and fit the pseudoscalar masses and decay constants to chiral perturbation theory. We infer as well the mass and decay constant of the Goldstone boson corresponding to the non-anomalous U(1) symmetry of the model. Our results are broadly consistent with large-Nc scaling and vector-meson dominance.
↳ hep-lathep-phPRD(2018)·103 citations
36*
Orbital fingerprints of ultralight scalar fields around black holes
Miguel C. Ferreira🇵🇹 · Caio F. B. Macedo🇵🇹 · Vitor Cardoso🇵🇹
Ultralight scalars have been predicted in a variety of scenarios, and advocated as a possible component of dark matter. These fields can form compact regular structures known as boson stars, or---in the presence of horizons---give rise to nontrivial time-dependent scalar hair and a stationary geometry. Because these fields can be coherent over large spatial extents, their interaction with "regular" matter can lead to very peculiar effects, most notably resonances. Here we study the motion of stars in a background describing black holes surrounded by non-axially symmetric scalar field profiles. By analyzing the system in a weak-field approach, we find that the presence of a scalar field gives rise to secular effects akin to ones existing in planetary and accretion disks. Particularly, the existence of resonances between the orbiting stars and the scalar field may enable angular momentum exchange between them, providing mechanisms similar to planetary migration. Additionally, these mechanisms may allow \textit{floating orbits}, which are stable radiating orbits. We also show, in the full relativistic case, that these effects also appear when there is a direct coupling between the scalar field and the stellar matter, which can arise due to the presence of a scalar core in the star or in alternative theories of gravity.
↳ gr-qchep-phPRD(2017)·89 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.