Thu·Sep 6, 2018Thursday·September 6, 2018

1. 01*

   Limits from BBN on Light Electromagnetic Decays

   Lindsay Forestell🇨🇦 · David E. Morrissey🇨🇦 · Graham White🇨🇦

   Injection of electromagnetic energy - photons, electrons, or positrons - into the plasma of the early universe can destroy light elements created by primordial Big Bang Nucleosynthesis (BBN). The success of BBN at predicting primordial abundances has thus been used to impose stringent constraints on decay or annihilation processes with primary energies near or above the electroweak scale. In this work we investigate the constraints from BBN on electromagnetic decays that inject lower energies, between 1-100 MeV. We compute the electromagnetic cascade from such injections and we show that it can deviate significantly from the universal spectrum commonly used in BBN calculations. For electron injection below 100 MeV, we find that the final state radiation of photons can have a significant impact on the resulting spectrum relevant for BBN. We also apply our results on electromagnetic cascades to investigate the limits from BBN on light electromagnetic decays prior to recombination, and we compare them to other bounds on such decays.

   hep-phastro-ph.COJHEP(2019)·84 citations
2. 02*

   Axion, photon-pair mixing in models of axion dark matter

   R. F. Sawyer🇺🇸

   A system of light axions comprising a classical axion field, one candidate for dark matter, has an instability that would rapidly mix in photon pairs in a coherent fashion if the system were initially seeded by some tiny amount of such mixing. We develop equations that contain the mixing and at the same time incorporate enough quantum mechanics to eliminate the need for seeds. Extending to many modes brings many interesting issues to the fore. For example, the argument of the inevitable logarithmic factor in the mixing time becomes reduced by many orders of magnitude; concerns concerning red-shifts are laid to rest, as are those related to lumpiness of the original axion state. We further see that even the fully developed states of the electromagnetic field are completely non-classical in our solutions.

   hep-ph8 citations
3. 03*

   Strong gravitational radiation from a simple dark matter model

   Iason Baldes🇩🇪 · Camilo Garcia-Cely🇩🇪

   A rather minimal possibility is that dark matter consists of the gauge bosons of a spontaneously broken symmetry. Here we explore the possibility of detecting the gravitational waves produced by the phase transition associated with such breaking. Concretely, we focus on the scenario based on an $SU(2{)}_D$ group and argue that it is a case study for the sensitivity of future gravitational wave observatories to phase transitions associated with dark matter. This is because there are few parameters and those fixing the relic density also determine the effective potential establishing the strength of the phase transition. Particularly promising for LISA and even the Einstein Telescope is the super-cool dark matter regime, with DM masses above $\mathcal{O}$(100) TeV, for which we find that the gravitational wave signal is notably strong. In our analysis, we include the effect of astrophysical foregrounds, which are often ignored in the context of phase transitions.

   hep-phastro-ph.COJHEP(2019)·151 citations
4. 04*

   Constraining nonlinear corrections to Maxwell electrodynamics using $\gamma \gamma$ scattering

   P. Niau Akmansoy🇧🇷 · L. G. Medeiros🇧🇷

   The recent light-by-light scattering cross section measurement made by the ATLAS\ Collaboration is used to constrain nonlinear corrections to Maxwell electrodynamics parametrized by the Lagrangian $L=F+4\alpha F^2+4\beta G^2+4\delta FG$. The ion's radiation is described using the equivalent photon approximation, and the influence of four different nuclear charge distributions is evaluated. Special attention is given to the interference term between the Standard Model and the nonlinear corrections amplitudes. By virtue of the quadratic dependence on $\alpha$, $\beta$ and $\delta$, the nonlinear contribution to the Standard Model $\gamma \gamma$ cross section is able to delimit a finite region of the parameter's phase space. The upper values for $\alpha$, $\beta$ in this region are of order $10^{-10}$GeV, a constraint of at least $12$ orders of magnitude more precise when compared to low-energy experiments. An upper value of the same order for $\delta$ is obtained for the first time in the LHC energy regime. We also give our predictions for the Standard Model cross section measured at ATLAS for each distribution and analyze the impact of the absorption factor. We finally give predictions for the future measurements to be done with upgraded tracking acceptance $\left|\eta \right|<4$ by the ATLAS Collaboration.

   hep-phhep-thPRD(2019)·29 citations
5. 05*

   On chiral excitations with exotic quantum numbers

   Xiao-Yu Guo🇩🇪 · Yonggoo Heo🇹🇭 · Matthias F.M. Lutz🇩🇪

   We consider the flavour sextet of charmed meson resonances with J^P= 1^+ quantum numbers that is predicted by the leading order chiral Lagrangian with up, down and strange quarks. The effect of chiral correction terms as determined previously from QCD lattice data is worked out. Pole masses in the complex energy plane are derived. The most promising signal from such states accessible in experiments like Belle, LHCb and PANDA are foreseen in the s-wave pi D* phase shift and the eta D* invariant mass distribution. For physical quark masses a rapid variation of the phase shift in between the eta D* and the bar K Ds* thresholds is predicted.

   hep-phPLB(2019)·16 citations
6. 06*

   Transverse momentum broadening and collinear radiation at NLO in the $\mathcal{N}=4$ SYM plasma

   Jacopo Ghiglieri🇨🇭 · HyungJoo Kim🇰🇷

   We compute O(g) NLO corrections to the transverse scattering kernel and transverse momentum broadening coefficient $\hat{q}$ of weakly-coupled $\mathcal{N}=4$ SYM. Based on this, we also compute NLO correction to the collinear splitting rates. For $\hat{q}$ we find that the NLO/LO ratio is similar to the QCD one, with large NLO corrections. This is contrasted by our findings for the collinear splitting rate, which show a much better convergence in SYM than in QCD, providing further support to earlier expectations that NLO corrections have signs and relative magnitudes controlled by the specifics of the theory. We also compare the ratio of $\hat{q}$ in QCD and in $\mathcal{N}=4$ theory to strong coupling expectations.

   hep-phhep-thnucl-thJHEP(2018)·22 citations
7. 07*

   Light scalars: coherent nonlinear Thomson scattering and detection

   Barry M. Dillon🇬🇧 · B. King🇬🇧

   Several theories of beyond-the-standard-model physics predict light scalars that couple to fermions. By extending classical electrodynamics to include an electron-scalar coupling, we calculate the nonlinear Thomson scattering of light scalars in the collision of an electron with a monochro- matic electromagnetic background. In doing so, we identify the classical electron-scalar current, which allows for straightforward inclusion of the process in laser-plasma particle-in-cell simulations. Scattering of pseudoscalar particles is found to vanish in the classical (or, equivalently, the low-lightfront-momentum) limit. When electrons co-propagate with the laser pulse, we demonstrate that coherence effects in the production of light scalar particles can greatly enhance the signal for sub-eV scalars. When the electron beams counter-propagate with the laser pulse, we demon- strate that experiments can probe larger scalar masses due to the larger momentum transfer in the collisions. We then discuss a possible lab-based experimental set-up to detect this scalar signal which is similar to light-shining-through-the-wall experiments. Using existing experimental facilities as benchmarks, we calculate projected exclusion bounds on the couplings of light scalars in such experiments.

   hep-phPRD(2019)·20 citations
8. 08*

   Studying flavor-changing neutral tqZ couplings: Current constraints and future prospects

   Zenro Hioki (U. Tokushima)🇯🇵 · Kazumasa Ohkuma (Okayama U. Science)🇯🇵 · Akira Uejima (Okayama U. Science)🇯🇵

   Possible non-standard tuZ and tcZ interactions, which induce flavor-changing neutral-current decays of the top quark, are studied in the effective-Lagrangian framework. The corresponding Lagrangian consists of four kinds of non-standard couplings coming from SU(3)xSU(2)xU(1) invariant dimension-6 effective operators. The four coupling constants in each interaction are treated as complex numbers independent of each other, and constraints on them are derived by using the present experimental limits of the branching fractions for t -> u Z and t -> c Z processes. Future improvements of those constraints are also discussed as well as possibilities of measurements of these couplings at the High-Luminosity Large Hadron Collider.

   hep-phhep-exMod.Phys.Lett.A(2019)·2 citations
9. 09*

   Planck Mass Charged Gravitino Dark Matter

   Krzysztof A. Meissner🇵🇱 · Hermann Nicolai🇩🇪

   Following up on our earlier work predicting fractionally charged supermassive gravitinos, we explain their potential relevance as novel candidates for Dark Matter and discuss possible signatures and ways to detect them.

   hep-phastro-ph.COPRD(2019)·26 citations
10. 10*

    NNLO soft function for top quark pair production at small transverse momentum

    Rene Angeles-Martinez🇵🇱 · Michal Czakon🇩🇪 · Sebastian Sapeta🇵🇱

    The cross section for top quark pair production factorizes at small transverse momentum of the heavy quark pair, $q_T$. One of the key ingredients that appears in the factorization formula is the soft function, which mediates soft gluon exchanges between particles and gives rise to colour correlations. We present the complete result for the small-$q_T$ soft function at the next-to-next-to-leading order. This is the last missing element needed to calculate the NNLO cross section for top quark pair production by means of the $q_T$ slicing method. In order to evaluate divergent integrals appearing in the calculation, we develop methods based on sector decomposition and differential equations. We present an extensive validation of our framework. In particular, we recover results predicted by the renormalization group, which constitutes a direct demonstration of validity of the small-$q_T$ factorization at NNLO. We provide complete results for the real and imaginary part of the soft function, which are ready for application in the calculation of the $t\bar{t}$ cross section at NNLO.

    hep-phJHEP(2018)·42 citations
11. 11*

    Search for the vectorlike leptons in the U(1)${}_X$ model inspired by the $B$-meson decay anomalies

    Fang-Zhou Xu🇨🇳 · Wenxing Zhang🇨🇳 · Jinmian Li🇰🇷 · Tianjun Li🇨🇳

    We consider the U(1)${}_X$ model, which can induce the flavor violating couplings through vectorlike fermions and address the observed rare $B$-meson decay anomalies. To be consistent with all the other observations, both the associated gauge boson mass and the vectorlike lepton mass are bounded from above. We argue that the search for new vectorlike leptons is promising and provides a complement to the $Z^{\prime }$ search. A detailed collider analysis shows that the model with the vectorlike lepton mass up to 1000 GeV could be tested at the future LHC.

    hep-phPRD(2018)·17 citations
12. 12*

    IR-improved DGLAP parton shower effects in W + jets in pp collisions at $\sqrt{s}=7$ TeV

    B. Shakerin🇺🇸 · B.F.L. Ward🇺🇸

    We use HERWIRI1.031, a new Monte Carlo event generator for hadron-hadron scattering at high energies, to study the phenomenological effects of our approach of exact amplitude-based resummation in precision QCD calculations. W + jet(s) events with exact NLO QCD corrections are generated in the MG5_aMC@NLO framework and showered by both HERWIRI1.031 and HERWIG6.5 with PTRMS = 0 and PTRMS = 2.2 GeV/c, respectively. Here, PTRMS is the rms value of the intrinsic Gaussian transverse momentum distribution for the partons inside the proton. The differential cross sections for many observables are presented such as the jet rapidities and the jet transverse momenta as well as other event observables such as the scalar sums of transverse momenta of the jets, the missing transverse energy of the jets and the dijets' observables. Finally, we compare our results with the ATLAS and CMS measurements of the W production cross sections in association with jets.

    hep-phPRD(2019)·5 citations
13. 13*

    Azimuthal Angular Decorrelation of Jets at Future High Energy Colliders

    I. Hos🇹🇷 · H. Saygin🇹🇷 · S. Kuday🇹🇷

    The azimuthal angular decorrelation that is relevant to small-x QCD physics is studied in this paper to show the BFKL effect with a recent event generator. Events are generated at \sqrt{s} = 100 TeV with proton-proton collisions and jets, that are reconstructed by the Anti-k_{T} algorithm (R=0.7), with p_{T}>35GeV and in the rapidity range of |y|<6 are selected for the study. The azimuthal-angle difference between Mueller-Navelet Jets (\Delta\text{{\Phi}} ) in the rapidity seperation (\Delta y) up to 12 is analysed. The distributions of <cosn(\pi-\Delta\Phi)> for n=1,2,3 and their ratio are also presented as a function of \Delta y.

    hep-phActa Phys.Polon.B(2019)·1 citation
14. 14*

    Pion Valence Quark Distributions from Maximum Entropy Method

    Chengdong Han🇨🇳 · Hanyang Xing🇨🇳 · Xiaopeng Wang🇨🇳 · Qiang Fu🇨🇳 · Rong Wang🇫🇷 · Xurong Chen🇨🇳

    Valence quark distributions of pion at very low resolution scale $Q_0^2\sim 0.1Ge{V}^2$ are deduced from a maximum entropy method, under the assumption that pion consists of only a valence quark and a valence anti-quark at such a low scale. Taking the obtained initial quark distributions as the nonperturbative input in the modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (with the GLR-MQ-ZRS corrections) evolution, the generated valence quark distribution functions at high $Q^2$ are consistent with the measured ones from a Drell-Yan experiment. The maximum entropy method is also applied to estimate the valence quark distributions at relatively higher $Q^2$ = 0.26 GeV${}^2$. At this higher scale, other components (sea quarks and gluons) should be considered in order to match the experimental data. The first three moments of pion quark distributions at high $Q^2$ are calculated and compared with the other theoretical predictions.

    hep-phPLB(2020)·27 citations
15. 15*

    Strangeness neutrality and baryon-strangeness correlations

    Wei-jie Fu🇨🇳 · Jan M. Pawlowski🇩🇪 · Fabian Rennecke🇺🇸

    We derive a simple relation between strangeness neutrality and baryon-strangeness correlations. In heavy-ion collisions, the former is a consequence of quark number conservation of the strong interactions while the latter are sensitive probes of the character of QCD matter. This relation allows us to directly extract baryon-strangeness correlations from the strangeness chemical potential at strangeness neutrality. The explicit calculations are performed within a low energy theory of QCD with 2+1 dynamical quark flavors at finite temperature and density. Non-perturbative quark and hadron fluctuations are taken into account within the functional renormalization group. The results show the pronounced sensitivity of baryon-strangeness correlations on the QCD phase transition and the crucial role that strangeness neutrality plays for this observable.

    hep-phnucl-thPRD(2019)·39 citations
16. 16*

    Searching for Axion Dark Matter with Birefringent Cavities

    Hongwan Liu🇺🇸 · Brodi D. Elwood🇺🇸 · Matthew Evans🇺🇸 · Jesse Thaler🇺🇸

    Axion-like particles are a broad class of dark matter candidates which are expected to behave as a coherent, classical field with a weak coupling to photons. Research into the detectability of these particles with laser interferometers has recently revealed a number of promising experimental designs. Inspired by these ideas, we propose the Axion Detection with Birefringent Cavities (ADBC) experiment, a new axion interferometry concept using a cavity that exhibits birefringence between its two, linearly polarized laser eigenmodes. This experimental concept overcomes several limitations of the designs currently in the literature, and can be practically realized in the form of a simple bowtie cavity with tunable mirror angles. Our design thereby increases the sensitivity to the axion-photon coupling over a wide range of axion masses.

    hep-phastro-ph.COphysics.ins-detphysics.opticsPRD(2019)·137 citations
17. 17*

    The non-equilibrium attractor for kinetic theory in relaxation time approximation

    Michael Strickland🇺🇸

    I demonstrate that the concept of a non-equilibrium attractor can be extended beyond the lowest-order moments typically considered in hydrodynamic treatments. Using a previously obtained exact solution to the relaxation-time approximation Boltzmann equation for a transversally homogeneous and boost-invariant system subject to Bjorken flow, I derive an equation obeyed by all moments of the one-particle distribution function. Using numerical solutions, I show that, similar to the pressure anisotropy, all moments of the distribution function exhibit attractor-like behavior wherein all initial conditions converge to a universal solution after a short time with the exception of moments which are sensitive to modes with zero longitudinal momentum and high transverse momentum. In addition, I compute the exact solution for the distribution function itself on very fine lattices in momentum space and demonstrate that (a) an attractor for the full distribution function exists and (b) solutions with generic initial conditions relax to this solution, first at low momentum and later at high momentum.

    ↳ nucl-thhep-phJHEP(2018)·129 citations
18. 18*

    The dS swampland conjecture with the electroweak symmetry and QCD chiral symmetry breaking

    Kiwoon Choi🇰🇷 · Dongjin Chway🇰🇷 · Chang Sub Shin🇰🇷

    The dS swampland conjecture $|\nabla V|/V\ge c$, where $c$ is presumed to be a positive constant of order unity, implies that the dark energy density of our Universe can not be a cosmological constant, but mostly the potential energy of an evolving quintessence scalar field. As the dark energy includes the effects of the electroweak symmetry breaking and the QCD chiral symmetry breaking, if the dS swampland conjecture is applicable for the low energy quintessence potential, it can be applied for the Higgs and pion potential also. On the other hand, the Higgs and pion potential has the well-known dS extrema, and applying the dS swampland conjecture to those dS extrema may provide stringent constraints on the viable quintessence, as well as on the conjecture itself. We examine this issue and find that the pion dS extremum at $\cos ({\pi }_0/f_{\pi })=-1$ implies $c\lesssim \mathcal{O}(10^{-2}-10^{-5})$ for $arbitrary$ form of the quintessence potential and couplings, where the weaker bound ($10^{-2}$) is available $only$ for a specific type of quintessence whose couplings respect the equivalence principle, while the stronger bound ($10^{-5}$) applies for generic quintessence violating the equivalence principle. We also discuss the possibility to relax this bound with an additional scalar field, e.g. a light modulus which has a runaway behavior at the pion dS extremum. We argue that such possibility is severely constrained by a variety of observational constraints which do not leave a room to significantly relax the bound. We make a similar analysis for the Higgs dS extremum at $H=0$, which results in a weaker bound on $c$.

    ↳ hep-thhep-phJHEP(2018)·75 citations
19. 19*

    Stringy black-hole gas in ${\alpha }^{\prime }$-corrected dilaton gravity

    Jerome Quintin🇨🇦 · Robert H. Brandenberger🇨🇦 · Maurizio Gasperini🇮🇹 · Gabriele Veneziano🇫🇷

    We discuss the properties of the gas of primordial `stringy' black holes possibly formed in the high-curvature phase preceding the bouncing transition to the phase of standard cosmological evolution. We show that the regime dominated by such a string-hole gas can be consistently described by explicit solutions of the string effective action including first-order ${\alpha }^{\prime }$ corrections. We present a phase space analysis of the stability of such solutions comparing the results obtained from different actions and including the possibility of $O(d,d)$-symmetric configurations.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2018)·28 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.