Fri·Jan 19, 2018Friday·January 19, 2018

1. 01*

   Thermal dark matter co-annihilating with a strongly interacting scalar

   S. Biondini🇨🇭 · M. Laine🇨🇭

   Recently many investigations have considered Majorana dark matter co-annihilating with bound states formed by a strongly interacting scalar field. However only the gluon radiation contribution to bound state formation and dissociation, which at high temperatures is subleading to soft 2->2 scatterings, has been included. Making use of a non-relativistic effective theory framework and solving a plasma-modified Schrodinger equation, we address the effect of soft 2->2 scatterings as well as the thermal dissociation of bound states. We argue that the mass splitting between the Majorana and scalar field has in general both a lower and an upper bound, and that the dark matter mass scale can be pushed at least up to 5...6 TeV.

   hep-phJHEP(2018)·67 citations
2. 02*

   D-term, strong forces in the nucleon, and their applications

   Maxim V. Polyakov🇷🇺 · Peter Schweitzer🇺🇸

   The D-term is a fundamental particle property which is defined through the matrix elements of the energy-momentum tensor and as such in principle on equal footing with mass and spin. Yet the experimental information on the D-term of any hadron is very scarce. The D-term of the nucleon can be inferred from studies of hard-exclusive reactions, and its measurement will give valuable insights on the dynamics, structure, and the internal forces inside the nucleon. We review the latest developments and the fascinating applications of the D-term and other energy-momentum tensor (EMT) form factors. We also suggest a definition of the mechanical mean square radius and make a prediction for its size.

   hep-ph17 citations
3. 03*

   Glauber-model analysis of 5 TeV $\mathbf{p}$-Pb centrality compared to a two-component (soft + hard) model of hadron production in high-energy nuclear collisions

   Thomas A. Trainor🇺🇸

   A recent study of 5 TeV $p$-Pb centrality combined a Glauber model of $p$-Pb collision geometry with an assumption of linear scaling between $n_{ch}$ (charge) integrated within some $\eta$ acceptance and the number of nucleon participants $N_{part}$. The study concluded that $N_{part}$ increases to nearly 16 in central collisions, and the high-$p_t$ region of $p$-Pb $p_t$ spectra rescaled by the Glauber-estimated number of $p$-N binary collisions remains consistent with a $p$-$p$ spectrum for the same energy, independent of $p$-Pb centrality. However, the relation between $N_{part}$ and $n_{ch}$ derived from a two-component (soft + hard) model (TCM) study of ensemble-mean ${\bar{p}}_t$ data for the same system is quite different. This article reports a detailed analysis of the Glauber study and the question of centrality in $p$-A collisions. The Glauber centrality model is compared with the ${\bar{p}}_t$ TCM to understand the sources of major differences. The assumption of linear proportionality between $n_{ch}$ and $N_{part}$ is found to be inconsistent with ${\bar{p}}_t$ data. Properties of the convolution integral relating a differential cross section and hadron production model to an event distribution on $n_{ch}$ are examined. An alternative differential-cross-section distribution is inferred from charge-multiplicity data, and the upper limit on $N_{part}$ is estimated to be near 8. The TCM centrality model is then applied to $p_t$ spectrum ratios to predict results for $p$-Pb spectra. The spectrum TCM is tested with identified-pion spectra from 5 TeV $p$-Pb collisions and the result is consistent with previous $p$-$p$ TCM results. A TCM prediction that the spectrum ratio at high $p_t$ should increase to 14 for central $p$-Pb collisions due to quadratic dependence of dijet production on $n_{ch}$ is consistent with ${\bar{p}}_t$ data from the same system.

   hep-ph21 citations
4. 04*

   Transverse Momentum Dependent Quasi-Parton-Distributions

   Xiangdong Ji🇨🇳 · Lu-Chang Jin🇺🇸 · Feng Yuan🇺🇸 · Jian-Hui Zhang🇩🇪 · Yong Zhao🇺🇸

   We investigate the transverse momentum dependent parton distributions (TMDs) in the quasi-parton-distribution framework. The long standing hurdle of the so-called pinch pole singularity from the space-like gauge links in the TMD definitions can be resolved by the finite length of the gauge link along the hadron moving direction. In addition, with the soft factor subtraction, the quasi-TMD is free of linear divergence. We further demonstrate that the energy evolution equation of the quasi-TMD a.k.a. the Collins-Soper evolution, only depends on the hadron momentum. This leads to a clear matching between the quasi-TMD and the standard TMDs.

   hep-phPRD(2019)·98 citations
5. 05*

   Modulus D-term Inflation

   Kenji Kadota🇰🇷 · Tatsuo Kobayashi🇯🇵 · Ikumi Saga🇯🇵 · Keigo Sumita🇯🇵

   We propose a new model of single-field D-term inflation in supergravity, where the inflation is driven by a single modulus field which transforms non-linearly under the U(1) gauge symmetry. One of the notable features of our modulus D-term inflation scenario is that the global U(1) remains unbroken in the vacuum and hence our model is not plagued by the cosmic string problem which can exclude most of the conventional D-term inflation models proposed so far due to the CMB observations.

   hep-phastro-ph.COhep-thJHEP(2018)·0 citations
6. 06*

   The radiative corrections to double-Dalitz decays revisited

   Karol Kampf🇨🇿 · Jiri Novotny🇨🇿 · Pablo Sanchez-Puertas🇨🇿

   In this study, we revisit and complete the full next-to-leading order corrections to pseudoscalar double-Dalitz decays within the soft-photon approximation. Comparing to the previous study, we find small differences, which are nevertheless relevant for extracting information about the pseudoscalar transition form factors. Concerning the latter, these processes could offer the opportunity to test them-for the first time-in their double-virtual regime

   hep-phhep-exnucl-thPRD(2018)·28 citations
7. 07*

   R*-operation and five-loop calculations

   B. Ruijl (Zurich, ETH)🇨🇭 · F. Herzog🇳🇱 · T. Ueda🇳🇱 · J.A.M. Vermaseren (NIKHEF, Amsterdam)🇳🇱 · A. Vogt (Liverpool U., Dept. Math.)🇬🇧

   We sketch how the R*-operation can be used to compute the pole terms of Feynman diagrams. We identify computational difficulties when performing five-loop calculations, and provide four solutions that drastically reduce the number of terms that are generated. Using these methods, we have computed the beta function for Yang-Mills theory with fermions, the R-ratio in electron-positron annihilation, and Higgs decays to quarks and gluons at five-loop accuracy. The results for the beta function and Higgs decay width to gluons in the heavy-top limit are briefly discussed. There is no need for six-loop extensions of these calculations in the near future.

   hep-phPoS(2018)·18 citations
8. 08*

   Four-loop results on anomalous dimensions and splitting functions in QCD

   A. Vogt (Liverpool U., Dept. Math.)🇬🇧 · S. Moch (Hamburg U., Inst. Theor. Phys. II)🇩🇪 · B. Ruijl (Zurich, ETH)🇨🇭 · T. Ueda🇳🇱 · J.A.M. Vermaseren (NIKHEF, Amsterdam)🇳🇱

   We report on recent progress on the flavour non-singlet splitting functions in perturbative QCD. The~exact four-loop (N^3LO) contribution to these functions has been obtained in the planar limit of a large number of colours. Phenomenologically sufficient approximate expressions have been obtained for the parts not exactly known so far. Both cases include results for the four-loop cusp and virtual anomalous dimensions which are relevant well beyond the evolution of non-singlet quark distributions, for which an accuracy of (well) below 1% has now been been reached.

   hep-phPoS(2018)·8 citations
9. 09*

   Observable windows for the QCD axion through $N_{\text{eff}}$

   Ricardo Z. Ferreira🇪🇸 · Alessio Notari🇪🇸

   We show that when the QCD axion is directly coupled to quarks with $c_q/f{\partial }_{\mu }a\bar{q}{\gamma }^{\mu }{\gamma }^{5}q$, such as in DFSZ models, the dominant production mechanism in the early universe at temperatures $1\mathrm{GeV}\lesssim T\lesssim 100\mathrm{GeV}$ is obtained via $q\bar{q}\leftrightarrow ga$ and $qg\leftrightarrow qa$, where $g$ are gluons. Different heavy quarks $q_i$ can produce a thermal axion background that decouples at a temperature $T_i$: (1) top quark at $T_t\lesssim 100\mathrm{GeV}$ for $f/c_t\lesssim 3\times 10^8\mathrm{GeV}$; (2) bottom quark at $T_b\lesssim m_b$, for $f/c_b\lesssim 8\times 10^7\mathrm{GeV}$; (3) charm quark at $T_c\lesssim m_c$ for $f/c_c\lesssim 5\times 10^7\mathrm{GeV}$. Each of these cases corresponds to a contribution to the effective number of relativistic degrees of freedom, in the windows given by $0.027\le \Delta N_{\text{eff}}\le 0.031$, $0.037\le \Delta N_{\text{eff}}\le 0.039$ and $0.039\le \Delta N_{\text{eff}}$, respectively. These contributions are larger than the one obtained when thermalization happens only above the electroweak phase transition, $\Delta N_{\mathrm{eff}}\lesssim 0.027$, and are within reach of future CMB S4 experiments, thus opening an alternative window to detect the axion and to test the early universe at such temperatures.

   hep-phastro-ph.COhep-thPRL(2018)·90 citations
10. 10*

    Combined analysis of double Higgs production via gluon fusion at the HL-LHC in the effective field theory approach

    Jeong Han Kim🇺🇸 · Yasuhito Sakaki🇰🇷 · Minho Son🇰🇷

    We perform the combined analysis of the double Higgs production via gluon fusion in the $b\bar{b}\gamma \gamma$ and $b\bar{b}{\tau }^{+}{\tau }^{-}$ decay channels at the High-Luminosity LHC (HL-LHC). To validate our analysis, we reproduce the ATLAS result of the $b\bar{b}\gamma \gamma$ process including all contributions from fakes. For the $b\bar{b}{\tau }^{+}{\tau }^{-}$ decay channel, we perform the similar analysis to the CMS one. As an improvement, we also perform the multivariate analysis employing the boosted decision tree algorithm. Then, we derive 68% probability contours on anomalous Higgs couplings in the effective field theory (EFT) approach for various analyses. We find that the $b\bar{b}{\tau }^{+}{\tau }^{-}$ process outperforms the $b\bar{b}\gamma \gamma$ for the measurement of energy-growing operators, while adding the $b\bar{b}{\tau }^{+}{\tau }^{-}$ process is least beneficial for improving the precision of the Higgs self-coupling (mainly set by the $b\bar{b}\gamma \gamma$ process). We illustrate that the double Higgs production alone can be comparable to the single Higgs process in constraining the modification of the top Yukawa coupling in the positive direction. Focusing on the Higgs self-coupling as a special interest, we derive the precision as a function of various improvable parameters such as tag and mistag rates of tau leptons, heavy flavor jets, photon identification, diphoton mass resolution, and jet energy resolution to take into account future phenomenological studies. As an optimistic benchmark scenario, we illustrate that the 68% and 95% probability intervals of the Higgs self-coupling, ${\lambda }_3/{\lambda }_3^{SM}$, at the HL-LHC can reach $[0.2,2.3]$ and $[-0.1,3.5]\cup [4.0,6.5]$, respectively, where the correlation among the EFT coefficients is taken into account.

    hep-phhep-exPRD(2018)·39 citations
11. 11*

    Colour Rearrangement for Dipole Showers

    Johannes Bellm🇸🇪

    We present an algorithm to rearrange the colour chains of dipole showers in the shower process according to the colour amplitudes of a simple matrix element. We implement the procedure in the dipole shower of Herwig and show comparisons to data.

    hep-phhep-exEPJC(2018)·13 citations
12. 12*

    Improved perturbative QCD formalism for $B_c$ meson decays

    Xin Liu🇨🇳 · Hsiang-nan Li🇹🇼 · Zhen-Jun Xiao🇨🇳

    We derive the $k_T$ resummation for doubly heavy-flavored $B_c$ meson decays by including the charm quark mass effect into the known formula for a heavy-light system. The resultant Sudakov factor is employed in the perutrbative QCD study of the "golden channel" $B_c^{+}\to J/\psi {\pi }^{+}$. With a reasonable model for the $B_c$ meson distribution amplitude, which maintains approximate on-shell conditions of both the partonic bottom and charm quarks, it is observed that the imaginary piece of the $B_c\to J/\psi$ transition form factor appears to be power suppressed, and the $B_c^{+}\to J/\psi {\pi }^{+}$ branching ratio is not lower than $10^{-3}$. The above improved perutrbative QCD formalism is applicable to $B_c$ meson decays to other charmonia and charmed mesons.

    hep-phhep-exhep-latPRD(2018)·32 citations
13. 13*

    Modifying dark matter indirect detection signals by thermal effects at freeze-out

    Andi Hektor🇪🇪 · Kristjan Kannike🇪🇪 · Ville Vaskonen🇪🇪

    We present an extension of the Standard Model, containing a fermion dark matter candidate and two real scalar singlets, where the observed dark matter abundance is produced via freeze-out before the electroweak phase transition. We show that in this case the dark matter annihilation channels determining its freeze-out are different from those producing indirect detection signal. We present a benchmark model where the indirect annihilation cross-section differs from the freeze-out one. The model also has a gravitational wave signature due to the first order electroweak phase transition.

    hep-phPRD(2018)·11 citations
14. 14*

    $f(T)$ gravity after GW170817 and GRB170817A

    Yi-Fu Cai🇨🇳 · Chunlong Li🇨🇳 · Emmanuel N. Saridakis🇬🇷 · LingQin Xue🇨🇳

    The combined observation of GW170817 and its electromagnetic counterpart GRB170817A reveals that gravitational waves propagate at the speed of light in high precision. We apply the effective field theory approach to investigate the experimental consequences for the theory of $f(T)$ gravity. We find that the speed of gravitational waves within $f(T)$ gravity is exactly equal to the light speed, and hence the constraints from GW170817 and GRB170817A are trivially satisfied. The results are verified through the standard analysis of cosmological perturbations. Nevertheless, by examining the dispersion relation and the frequency of cosmological gravitational waves, we observe a deviation from the results of General Relativity, quantified by a new parameter. Although its value is relatively small in viable $f(T)$ models, its possible future measurement in advancing gravitational-wave astronomy would be the smoking gun of testing this type of modified gravity.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2018)·164 citations
15. 15*

    Understanding the spectral hardenings and radial distribution of Galactic cosmic rays and Fermi diffuse gamma-rays with spatially-dependent propagation

    Yi-Qing Guo🇨🇳 · Qiang Yuan🇨🇳

    Recent direct measurements of Galactic cosmic ray spectra by balloon/space-borne detectors reveal spectral hardenings of all major nucleus species at rigidities of a few hundred GV. The all-sky diffuse gamma-ray emissions measured by the Fermi Large Area Telescope also show spatial variations of the intensities and spectral indices of cosmic rays. These new observations challenge the traditional simple acceleration and/or propagation scenario of Galactic cosmic rays. In this work we propose a spatially-dependent diffusion scenario to explain all these phenomena. The diffusion coefficient is assumed to be anti-correlated with the source distribution, which is a natural expectation from the charged particle transportation in turbulent magnetic field. The spatially-dependent diffusion model also gives a lower level of anisotropies of cosmic rays, which are consistent with observations by underground muons and air shower experiments. The spectral variations of cosmic rays across the Galaxy can be properly reproduced by this model.

    ↳ astro-ph.HEhep-phPRD(2018)·80 citations
16. 16*

    The origin of multi-TeV flares from the nearest blazar Markarian 421

    Sarira Sahu🇲🇽 · Alberto Rosales de León🇲🇽 · Shigehiro Nagataki🇯🇵 · Virendra Gupta🇲🇽

    Markarian 421 is a high-peaked BL Lac object and it has undergone many strong outbursts since its discovery as a TeV source in 1992. Markarian 421 has been stud- ied intensively and was observed by various Cherenkov tele- scope arrays ever since. The outbursts of April 2004 observed by the Whipple telescope and of February 2010 by the HESS telescopes are explained well in this work by using the photohadronic model. To account for the attenuation of these high- energy gamma-rays by the extragalactic background light (EBL), we use template EBL models. The intrinsic spectrum of each epoch is different even though the high-energy protons have almost the same spectral index. We observe that this difference in intrinsic spectra is due to the change in the spectral index of the low-energy tail of the synchrotron self Compton (SSC) photons during different epochs of flaring. Our results show that the contemporaneous multiwavelength observations, particularly in the low-energy tail region of the SSC emission of the source, are important in explaining the flaring phenomenon.

    ↳ astro-ph.HEhep-phEPJC(2018)·9 citations
17. 17*

    Primordial black holes with an accurate QCD equation of state

    Christian T. Byrnes🇬🇧 · Mark Hindmarsh🇫🇮 · Sam Young🇬🇧 · Michael R. S. Hawkins🇬🇧

    Making use of definitive new lattice computations of the Standard Model thermodynamics during the quantum chromodynamic (QCD) phase transition, we calculate the enhancement in the mass distribution of primordial black holes (PBHs) due to the softening of the equation of state. We find that the enhancement peaks at approximately $0.7M_{\odot }$, with the formation rate increasing by at least two orders of magnitude due to the softening of the equation of state at this time, with a range of approximately $0.3M_{\odot }<M<1.4M_{\odot }$ at full width half-maximum. PBH formation is increased by a smaller amount for PBHs with masses spanning a large range, $10^{-3}{M}_{\odot }<M_{\mathrm{PBH}}<10^3{M}_{\odot }$, which includes the masses of the BHs that LIGO detected. The most significant source of uncertainty in the number of PBHs formed is now due to unknowns in the formation process, rather than from the phase transition. A near scale-invariant density power spectrum tuned to generate a population with mass and merger rate consistent with that detected by LIGO should also produce a much larger energy density of PBHs with solar mass. The existence of BHs below the Chandresekhar mass limit would be a smoking gun for a primordial origin and they could arguably constitute a significant fraction of the cold dark matter density. They also pose a challenge to inflationary model building which seek to produce the LIGO BHs without overproducing lighter PBHs.

    ↳ astro-ph.COhep-phJCAP(2018)·255 citations
18. 18*

    Open bottom mesons in asymmetric nuclear matter in presence of strong magnetic fields

    Nikhil Dhale🇮🇳 · Sushruth P Reddy🇮🇳 · Amal Jahan CS🇮🇳 · Amruta Mishra🇮🇳

    The modifications of the masses of the $B$ and $\bar{B}$ mesons in asymmetric nuclear matter in the presence of strong magnetic fields, are investigated using a chiral effective model. The medium modifications of these open bottom mesons arise due to their interactions with the scalar mesons and the nucleons. In the magnetized nuclear matter, the proton has contributions from the Landau levels. In the chiral effective model, the masses of the $B$ and $\bar{B}$ are calculated from the leading term, namely the vectorial Weinberg Tomozawa term as well as from the next to leading order contributions, i.e., due to the scalar exchange and the range terms. Due to the Weinberg-Tomozawa term, the $\bar{B}$ mesons experience an attractive interaction in the symmetric nuclear matter, whereas the $B$ mesons have a repulsive interaction. Inclusion of the contributions from the scalar exchange and the range terms as well, leads to drop of the masses of both $B$ and $\bar{B}$ mesons. The effect of the isospin asymmetry breaks the mass degeneracy of the $B^{+}$ and $B^0$ (as well as of the $B^{-}$ and $\overline{B^0}$) mesons, and its effect is observed to be large at high densities. The effects of anomalous magnetic moments of the nucleons are taken into account in the present study of the masses of the open bottom mesons in magnetized nuclear matter.

    ↳ nucl-thhep-phPRC(2018)·40 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.