Fri·Jul 29, 2016Friday·July 29, 2016

1. 01*

   IC at IC: IceCube can constrain the intrinsic charm of the proton

   Ranjan Laha🇺🇸 · Stanley J. Brodsky🇺🇸

   The discovery of extraterrestrial neutrinos in the $\sim$ 30 TeV -- PeV energy range by IceCube provides new constraints on high energy astrophysics. An important background to the signal are the prompt neutrinos which originate from the decay of charm hadrons produced by high energy cosmic-ray particles interacting in the Earth's atmosphere. It is conventional to use the calculations of charm hadroproduction using gluon splitting $g\to c\bar{c}$ alone. However, QCD predicts an additional "intrinsic" component of the heavy quark distribution which arises from diagrams where heavy quarks are multiply connected to the proton's valence quarks. We estimate the prompt neutrino spectrum due to intrinsic charm. We find that the atmospheric prompt neutrino flux from intrinsic charm is comparable to those calculated using QCD computations not including intrinsic charm, once we normalize the intrinsic charm differential cross sections to the ISR and the LEBC-MPS collaboration data. In future, IceCube will constrain the intrinsic charm content of the proton and will contribute to one of the major questions in high energy physics phenomenology.

   hep-phastro-ph.HEhep-exnucl-ex+1PRD(2017)·54 citations
2. 02*

   Regularization-scheme dependence of QCD amplitudes in the massive case

   Christoph Gnendiger🇨🇭 · Adrian Signer🇨🇭 · Andrea Visconti🇨🇭

   We investigate QCD amplitudes with massive quarks computed in the four-dimensional helicity scheme (FDH) and dimensional reduction at NNLO and describe how they are related to the corresponding amplitudes computed in conventional dimensional regularization. To this end, the scheme dependence of the heavy quark and the velocity-dependent cusp anomalous dimensions is determined using soft-collinear effective theory. The results are checked against explicit computations of massive form factors in FDH at NNLO. Our results complete the description of the scheme dependence of QCD amplitudes at NNLO.

   hep-phJHEP(2016)·14 citations
3. 03*

   Matching Matters!

   Ayres Freitas🇺🇸 · David Lopez-Val🇧🇪 · Tilman Plehn🇩🇪

   Effective Lagrangians are a useful tool for a data-driven approach to physics beyond the Standard Model at the LHC. However, for the new physics scales accessible at the LHC, the effective operator expansion is only relatively slowly converging at best. For tree-level processes, it has been found that the agreement between the effective Lagrangian and a range of UV-complete models depends sensitively on the appropriate definition of the matching. We extend this analysis to the one-loop level, which is relevant for electroweak precision data and Higgs decay to photons. We show that near the scale of electroweak symmetry breaking the validity of the effective theory description can be systematically improved through an appropriate matching procedure. In particular, we find a significant increase in accuracy when including suitable terms suppressed by the Higgs vacuum expectation value in the matching.

   hep-phPRD(2016)·22 citations
4. 04*

   Limits on Spherical Coefficients in the Minimal-SME Photon Sector

   W.J. Jessup🇺🇸 · N.E. Russell🇺🇸

   We place limits on spherical coefficients for Lorentz violation involving operators of dimension four in the photon sector of the minimal Standard-Model Extension. The bounds are deduced from existing experimental results with optical-cavity oscillators.

   hep-ph1 citation
5. 05*

   Preliminary Design of a Pendulum Experiment for Searching for a Lorentz-Violation Signal

   Cheng-Gang Shao🇨🇳 · Ya-Fen Chen🇨🇳 · Yu-Jie Tan🇨🇳

   This work mainly presents a preliminary design for a pendulum experiment with both the source mass and the test mass in a striped pattern to amplify the Lorentz-violation signal, since the signal is sensitive to edge effects.

   hep-ph1 citation
6. 06*

   Sparticles in Motion - getting to the line in compressed scenarios with the Recursive Jigsaw Reconstruction

   Paul Jackson🇦🇺 · Christopher Rogan🇺🇸 · Marco Santoni🇦🇺

   The observation of light super-partners from a supersymmetric extension to the Standard Model is an intensely sought-after experimental outcome, providing an explanation for the stabilization of the electroweak scale and indicating the existence of new particles which could be consistent with dark matter phenomenology. For compressed scenarios, where sparticle spectra mass-splittings are small and decay products carry low momenta, dedicated techniques are required in all searches for supersymmetry. In this paper we suggest an approach for these analyses based on the concept of Recursive Jigsaw Reconstruction, decomposing each event into a basis of complementary observables, for cases where strong initial state radiation has sufficient transverse momentum to elicit the recoil of any final state sparticles. We introduce a collection of kinematic observables which can be used to probe compressed scenarios, in particular exploiting the correlation between missing momentum and that of radiative jets. As an example, we study squark and gluino production, focusing on mass-splittings between parent super-particles and their lightest decay products between 25 and 200 GeV, in hadronic final states where there is an ambiguity in the provenance of reconstructed jets.

   hep-phhep-exPRD(2017)·96 citations
7. 07*

   X(16.7) as the Solution of NuTeV Anomaly

   Yi Liang🇨🇳 · Long-Bin Chen🇨🇳 · Cong-Feng Qiao🇨🇳

   A recent experimental study of excited ${}^{8}Be$ decay to its ground state reveals an anomaly in the final states angle distribution. This exceptional result is attributed to a new vector gauge boson X(16.7). We study the significance of this new boson, especially its effect in anomalies observed in long-lasting experimental measurements. By comparing the discrepancies between the standard model predictions and the experimental results, we manage to find out the values and regions of the couplings of X(16.7) to muon and muon neutrino. In this work, we find that the newly observed boson X(16.7) may be the solution of both NuTeV anomaly and the $(g-2{)}_{\mu }$ puzzle.

   hep-phCPC(2017)·39 citations
8. 08*

   Direct CP Violation in Charmless Three-body Decays of $B$ Mesons

   Hai-Yang Cheng🇹🇼 · Chun-Khiang Chua🇹🇼 · Zhi-Qing Zhang🇨🇳

   Direct CP violation in charmless three-body hadronic decays of $B$ mesons is studied within the framework of a simple model based on the factorization approach. Three-body decays of heavy mesons receive both resonant and nonresonant contributions. Dominant nonresonant contributions to tree-dominated and penguin-dominated three-body decays arise from the $b\to u$ tree transition and $b\to s$ penguin transition, respectively. The former can be evaluated in the framework of heavy meson chiral perturbation theory with some modification, while the latter is governed by the matrix element of the scalar density $⟨M_1{M}_2|{\bar{q}}_1{q}_2|0⟩$. Strong phases in this work reside in effective Wilson coefficients, propagators of resonances and the matrix element of scalar density. In order to accommodate the branching fraction and CP asymmetries observed in $B^{-}\to K^{-}{\pi }^{+}{\pi }^{-}$, the matrix element $⟨K\pi |\bar{s}q|0⟩$ should have an additional strong phase, which might arise from some sort of power corrections such as final-state interactions. We calculate inclusive and regional CP asymmetries and find that nonresonant CP violation is usually much larger than the resonant one and that the interference effect is generally quite significant. If nonresonant contributions are turned off in the $K^{+}{K}^{-}{K}^{-}$ mode, the predicted CP asymmetries due to resonances will be wrong in sign when confronted with experiment. In our study of $B^{-}\to {\pi }^{-}{\pi }^{+}{\pi }^{-}$, we find that ${\mathcal{A}}_{CP}({\rho }^0{\pi }^{-})$ should be positive in order to account for CP asymmetries observed in this decay. However, all theories predict a large and negative CP violation in $B^{-}\to {\rho }^0{\pi }^{-}$. Measurements of CP-asymmetry Dalitz distributions put very stringent constraints on the theoretical models. We check the magnitude and the sign of violation in some (large) invariant mass regions to test our model.

   hep-phhep-exPRD(2016)·94 citations
9. 09*

   Zeros in the magic neutrino mass matrix

   Radha Raman Gautam🇮🇳 · Sanjeev Kumar🇮🇳

   We study the phenomenological implications of the presence of two zeros in a magic neutrino mass matrix. We find that only two such patterns of the neutrino mass matrix are experimentally acceptable. We express all the neutrino observables as functions of one unknown phase $\varphi$ and two known parameters $\Delta m_{12}^2$, $r=\Delta m_{12}^2/\Delta m_{23}^2$. In particular, we find ${\sin }^2{\theta }_{13}=(2/3)r/(1+r)$. We also present a mass model for the allowed textures based upon the group $A_4$ using type I+II see-saw mechanism.

   hep-phPRD(2016)·33 citations
10. 10*

    Amplitude determination for $MM\to MM$, $M=\pi ,K$ and cross-sections for $\gamma \gamma \to {\pi }^{+}{\pi }^{-},{\pi }^0{\pi }^0,{\pi }^0\eta$ in a chiral model

    S.P. Klevansky🇩🇪 · R.H. Lemmer🇿🇦 · Alireza Beygi🇩🇪

    Dai and Pennington have performed a comprehensive analysis of essentially all pion and kaon pair production data from two-photon collisions below 1.5 GeV, including all high statistics results from Belle, as well as the older data from Mark II at SLAC, CELLO at DESY, and Crystal Ball at SLAC. Imposing the basic constraints required by analyticity, unitarity, and crossing symmetry and making use of Low's low-energy theorem for QED, they were able to extract the final-state, strong-interaction scattering amplitudes for the intermediate $\pi \pi \to \pi \pi$ and $\pi \pi \to K\overline{K}$ reactions in a model-independent fashion. In addition, they provided good fits to the respective $\gamma \gamma \to \pi \pi$ cross-sections that are known in the low-energy sector in the restricted angular range, $|\cos \theta |<0.6-0.8$. Using the parameters obtained in this fashion, these authors constructed the $\gamma \gamma \to \pi \pi$ cross-sections integrated over the full angular range. In the present work, we use a version of chiral perturbation theory developed by Oller and Oset to evaluate the final-state, strong-interaction amplitudes theoretically, and we compare our low-energy QCD-based results with the amplitudes extracted by Dai and Pennington. We also calculate the $\gamma \gamma \to \pi \pi$ cross-sections (integrated over the full angular range) and compare them with those obtained by Dai and Pennington. These calculations give a more detailed insight into the fit of chiral perturbation theory, not just to the measured $\gamma \gamma \to \pi \pi$ cross-sections, as is usually presented, but rather to a higher level of detail through the available analysis of the experimental data for the underlying final-state, strong-interaction, meson-meson scattering amplitudes $\pi \pi \to \pi \pi$ and $\pi \pi \to K\overline{K}$ themselves. The fits appear to be sensible.

    hep-phEPJA(2025)·3 citations
11. 11*

    Precision Measurements in Electron-Positron Annihilation: Theory and Experiment

    Konstantin Chetyrkin🇩🇪 · Johann H. Kühn🇩🇪

    Theory results on precision measurements in electron-positron annihilation at low and high energies are collected. These cover pure QCD calculations as well as mixed electroweak and QCD results, involving light and heavy quarks. The impact of QCD corrections on the $W$-boson mass is discussed and, last not least, the status and the perspectives for the Higgs boson decay rate into $b\bar{b}$, $c\bar{c}$ and into two gluons.

    hep-ph3 citations
12. 12*

    The two-loop electroweak bosonic corrections to ${\sin }^2{\theta }_{\mathrm{eff}}^{\mathrm{b}}$

    Ievgen Dubovyk🇩🇪 · Ayres Freitas🇺🇸 · Janusz Gluza🇵🇱 · Tord Riemann🇵🇱 · Johann Usovitsch🇩🇪

    The prediction of the effective electroweak mixing angle ${\sin }^2{\theta }_{\mathrm{eff}}^{\mathrm{b}}$ in the Standard Model at two-loop accuracy has now been completed by the first calculation of the bosonic two-loop corrections to the $Z\bar{b}b$ vertex. Numerical predictions are presented in the form of a fitting formula as function of $M_Z,M_W,M_H,m_t$ and $\Delta \alpha$, ${\alpha }_{\mathrm{s}}$. For central input values, we obtain a relative correction of $\Delta {\kappa }_{\mathrm{b}}^{({\alpha }^2,\mathrm{bos})}=-0.9855\times 10^{-4}$, amounting to about a quarter of the fermionic corrections, and corresponding to ${\sin }^2{\theta }_{\mathrm{eff}}^{\mathrm{b}}=0.232704$. The integration of the corresponding two-loop vertex Feynman integrals with up to three dimensionless parameters in Minkowskian kinematics has been performed with two approaches: (i) Sector decomposition, implemented in the packages FIESTA 3 and SecDec 3, and (ii) Mellin-Barnes representations, implemented in AMBRE 3/MB and the new package MBnumerics.

    hep-phPLB(2016)·70 citations
13. 13*

    Analysis of DIS structure functions of the nucleon within truncated Mellin moments approach

    D. Kotlorz🇵🇱 · A. Kotlorz🇵🇱

    We present generalized evolution equations and factorization in terms of the truncated Mellin moments (TMM) of the parton distributions and structure functions. We illustrate the $x$ and $Q^2$ dependence of TMM in the polarized case. Using the TMM approach we compare the integrals of $g_1$ with HERMES and COMPASS data from the limited $x$-ranges.

    hep-phInt.J.Mod.Phys.A(2016)·8 citations
14. 14*

    Interplay of Infrared Divergences and Gauge-Dependence of the Effective Potential

    J.R. Espinosa🇪🇸 · M. Garny🇨🇭 · T. Konstandin🇩🇪

    The perturbative effective potential suffers infrared (IR) divergences in gauges with massless Goldstones in their minima (like Landau or Fermi gauges) but the problem can be fixed by a suitable resummation of the Goldstone propagators. When the potential minimum is generated radiatively, gauge-independence of the potential at the minimum also requires resummation and we demonstrate that the resummation that solves the IR problem also cures the gauge-dependence issue, showing this explicitly in the Abelian Higgs model in Fermi gauge. In the process we find an IR divergence (in the location of the minimum) specific to Fermi gauge and not appreciated in recent literature. We show that physical observables can still be computed in this gauge and we further show how to get rid of this divergence by a field redefinition. All these results generalize to the Standard Model case.

    hep-phhep-thPRD(2016)·48 citations
15. 15*

    Test of Lorentz Violation with Astrophysical Neutrino Flavor

    Teppei Katori🇬🇧 · Carlos A. Argüelles🇺🇸 · Jordi Salvado🇪🇸

    The high-energy astrophysical neutrinos recently discovered by IceCube opened a new way to test Lorentz and CPT violation through the astrophysical neutrino mixing properties. The flavor ratio of astrophysical neutrinos is a very powerful tool to investigate tiny effects caused by Lorentz and CPT violation. There are 3 main findings; (1) current limits on Lorentz and CPT violation in neutrino sector are not tight and they allow for any flavor ratios, (2) however, the observable flavor ratio on the Earth is tied with the flavor ratio at production, this means we can test both the presence of new physics and the astrophysical neutrino production mechanism simultaneously, and (3) the astrophysical neutrino flavor ratio is one of the most stringent tests of Lorentz and CPT violation.

    hep-ph6 citations
16. 16*

    Multipartite Interacting Scalar Dark Matter in the light of updated LUX data

    Subhaditya Bhattacharya🇮🇳 · Purusottam Ghosh🇮🇳 · Poulose Poulose (IIT Guwahati)🇮🇳

    We explore constraints on multipartite dark matter (DM) framework composed of singlet scalar DM interacting with the Standard Model (SM) through Higgs portal coupling. We compute relic density and direct search constraints including the updated LUX bound for two component scenario with non-zero interactions between two DM components in ${\mathcal{Z}}_2\times {\mathcal{Z}}_2^{{}^{\prime }}$ framework in comparison with the one having $\mathcal{O}(2)$ symmetry. We point out availability of a significantly large region of parameter space of such a multipartite model with DM-DM interactions.

    hep-phJCAP(2017)·116 citations
17. 17*

    Non-standard interactions and the CP phase measurements in neutrino oscillations at low energies

    Shao-Feng Ge🇩🇪 · Alexei Yu. Smirnov🇩🇪

    We study the effects of non-standard interactions (NSI) and the genuine CP phase ${\delta }_D$ in neutrino oscillations at low, $E_{\nu }\lesssim 1\text{mbox}GeV$, and very low, $E_{\nu }\lesssim 0.1\text{mbox}GeV$, energies. For experimental setup with baseline and neutrino energy tuned to the first 1-3 oscillation maximum, we develop a simple analytic formalism to show the effects of NSI. The vacuum mimicking and its violation as well as the use of the separation basis play a central role in our formalism. The NSI corrections that affect the CP phase measurement mainly come from the violation of vacuum mimicking as well as from the corrections to the 1-3 mixing angle and mass-squared difference. We find that the total NSI correction to the ${\nu }_{\mu }-{\nu }_e$ probability $P_{\mu e}$ can reach $20\%-30\%$ ($1\sigma$) at T2(H)K. Correspondingly, the correction to the CP phase can be as large as $50^{\circ }$ and hence significantly deteriorates the CP sensitivity at T2(H)K. The proposed TNT2K experiment, a combination of T2(H)K and the short baseline experiment $\mu$Kam that uses the Super-K/Hyper-K detector at Kamioka to measure the oscillation of the antineutrinos from muon decay at rest ($\mu$DAR), can substantially reduce the degeneracy between NSI and the genuine CP phase ${\delta }_D$ to provide high CP sensitivity. The NSI correction to $P_{\mu e}$ is only $2\%$ ($1\sigma$) for $\mu$DAR neutrinos.

    hep-phhep-exJHEP(2016)·69 citations
18. 18*

    Phenomenology of 2HDM with VLQs

    A. Arhrib🇲🇦 · R. Benbrik🇲🇦 · S.J.D. King🇬🇧 · B. Manaut🇲🇦 · S. Moretti🇬🇧 · C.S. Un🇹🇷

    In this paper, we examine the consistency of the Large Hadron Collider (LHC) data collected during Run 1 and 2 by the ATLAS and CMS experiments with the predictions of a 2-Higgs Doublet Model (2HDM) embedding Vector-Like Quarks (VLQs) for $pp\to H,A$ production and $H,A\to \gamma \gamma$ decay mechanisms, respectively, of (nearly) degenerate CP-even ($H$) and CP-odd ($A$) Higgs bosons. We show that a scenario containing one single VLQ with Electro-Magnetic (EM) charge $2/3$ can explain the above ATLAS and CMS data for masses in the region 350 GeV $\le m_{\mathrm{VLQ}}\le 1.5$ TeV or so, depending on $\tan \beta$, and for several values of the mixing angle between the top quark ($t$) and its VLQ counterpart ($T$).We then perform a global fit onto the model by including all relevant experimental as well as theoretical constraints. The surviving samples of our analysis are discussed within 2$\sigma$ of the LHC measurements. Additionally, we also comment on the recent anomalous result reported by CMS using Run 2 data on the associated Standard Model (SM) Higgs boson production with top quark pairs $pp\to t\bar{t}h$ with an observed significance of 3.3$\sigma$. Other than these specific examples, we also present a phenomenological analysis of the main features of the model, including the most promising $T$ decay channels.

    hep-phPRD(2018)·46 citations
19. 19*

    Relic Abundance in a Secluded Dark Matter Scenario with a Massive Mediator

    Shohei Okawa🇯🇵 · Masaharu Tanabashi🇯🇵 · Masato Yamanaka🇯🇵

    The relic abundance of the dark matter (DM) particle $d$ is studied in a secluded DM scenario, in which the $d$ number decreasing process dominantly occurs not through the pair annihilation of $d$ into the standard model particles, but via the $dd\to mm$ scattering process with a subsequently decaying mediator particle $m$. It is pointed out that the cosmologically observed relic abundance of DM can be accomplished even with a massive mediator having a mass $m_m$ non-negligibly heavy compared with the DM particle mass $m_d$. In the degenerated $d$-$m$ case ($m_d=m_m$), the DM relic abundance is realized by adjusting the $dd\to mm$ scattering amplitude large enough and by choosing an appropriate mediator particle life-time. The DM evolution in the early universe exhibits characteristic "terrace" behavior, or two-step number density decreasing behavior, having a "fake" freeze-out at the first step. Based on these observations, a novel possibility of the DM model buildings is introduced in which the mediator particle $m$ is unified with the DM particle $d$ in an approximate dark symmetry multiplet. A pionic DM model is proposed to illustrate this idea in a renormalizable field theory framework.

    hep-phPRD(2017)·34 citations
20. 20*

    General Electromagnetic Nonminimal Couplings in the Dirac Equation

    J. B. Araujo🇧🇷 · Rodolfo Casana🇧🇷 · M. M. Ferreira Jr🇧🇷

    We examine a new class of CPT-even and dimension-five nonminimal interactions between fermions and photons, deprived of higher-order derivatives, yielding electric dipole moment and magnetic dipole moment in the context of the Dirac equation. These couplings are Lorentz-violating nonminimal structures, composed of a rank-2 tensor, the electromagnetic tensor, and gamma matrices, being addressed in its axial and non-axial hermitian versions. We use the electron's anomalous magnetic and electric dipole moment measurements to reach upper bounds of $1$ part in $10^{11}$ and $10^{16}$ GeV${}^{-1}$.

    hep-phhep-th1 citation
21. 21*

    Testing neutrino mass generation mechanisms from the lepton flavor violating decay of the Higgs boson

    Mayumi Aoki🇯🇵 · Shinya Kanemura🇯🇵 · Kodai Sakurai🇯🇵 · Hiroaki Sugiyama🇯🇵

    We investigate how observations of the lepton flavor violating decay of the Higgs boson ($h\to \ell {\ell }^{\prime }$) can narrow down models of neutrino mass generation mechanisms, which were systematically studied in Refs. [1,2] by focusing on the combination of new Yukawa coupling matrices with leptons. We find that a wide class of models for neutrino masses can be excluded if evidence for $h\to \ell {\ell }^{\prime }$ is really obtained in the current or future collider experiments. In particular, simple models of Majorana neutrino masses cannot be compatible with the observation of $h\to \ell {\ell }^{\prime }$. It is also found that some of the simple models to generate masses of Dirac neutrinos radiatively can be compatible with a significant rate of the $h\to \ell {\ell }^{\prime }$ process.

    hep-phPLB(2016)·16 citations
22. 22*

    Testing Gravity on Accelerators

    Tigran Kalaydzhyan🇺🇸

    Weak equivalence principle (WEP) is one of the cornerstones of the modern theories of gravity, stating that the trajectory of a freely falling test body is independent of its internal structure and composition. Even though WEP is known to be valid for the normal matter with a high precision, it has never been experimentally confirmed for relativistic matter and antimatter. We make an attempt to constrain possible deviations from WEP utilizing the modern accelerator technologies. We analyze the (absence of) vacuum Cherenkov radiation, photon decay, anomalous synchrotron losses and the Compton spectra to put limits on the isotropic Lorentz violation and further convert them to the constraints on the difference between the gravitational and inertial masses of the relativistic electrons/positrons. Our main result is the 0.1% limit on the mentioned difference.

    hep-phgr-qc4 citations
23. 23*

    Future CMB tests of dark matter: ultra-light axions and massive neutrinos

    Renée Hložek🇨🇦 · David J. E. Marsh🇬🇧 · Daniel Grin🇺🇸 · Rupert Allison🇬🇧 · Jo Dunkley🇬🇧 · Erminia Calabrese🇬🇧

    Measurements of cosmic microwave background (CMB) anisotropies provide strong evidence for the existence of dark matter and dark energy. They can also test its composition, probing the energy density and particle mass of different dark-matter and dark-energy components. CMB data have already shown that ultra-light axions (ULAs) with mass in the range $10^{-32}\mathrm{eV}\to 10^{-26}\mathrm{eV}$ compose a fraction $<0.01$ of the cosmological critical density. Here, the sensitivity of a proposed CMB-Stage IV (CMB-S4) experiment (assuming a 1 arcmin beam and $<1\mu K-\mathrm{arcmin}$ noise levels over a sky fraction of 0.4) to the density of ULAs and other dark-sector components is assessed. CMB-S4 data should be $\sim 10$ times more sensitive to the ULA energy-density than Planck data alone, across a wide range of ULA masses $10^{-32}<m_a<10^{-23}\mathrm{eV}$, and will probe axion decay constants of $f_a\approx 10^{16}\mathrm{GeV}$, at the grand unified scale. CMB-S4 could improve the CMB lower bound on the ULA mass from $\sim 10^{-25}\mathrm{eV}$ to $10^{-23}\mathrm{eV}$, nearing the mass range probed by dwarf galaxy abundances and dark-matter halo density profiles. These improvements will allow for a multi-$\sigma$ detection of percent-level departures from CDM over a wide range of masses. Much of this improvement is driven by the effects of weak gravitational lensing on the CMB, which breaks degeneracies between ULAs and neutrinos. We also find that the addition of ULA parameters does not significantly degrade the sensitivity of the CMB to neutrino masses. These results were obtained using the axionCAMB code (a modification to the CAMB Boltzmann code), presented here for public use.

    ↳ astro-ph.COhep-phPRD(2017)·117 citations
24. 24*

    Moduli Backreaction on Inflationary Attractors

    Diederik Roest🇳🇱 · Marco Scalisi🇳🇱 · Pelle Werkman🇳🇱

    We investigate the interplay between moduli dynamics and inflation, focusing on the KKLT-scenario and cosmological $\alpha$-attractors. General couplings between these sectors can induce a significant backreaction and potentially destroy the inflationary regime; however, we demonstrate that this generically does not happen for $\alpha$-attractors. Depending on the details of the superpotential, the volume modulus can either be stable during the entire inflationary trajectory, or become tachyonic at some point and act as a waterfall field, resulting in a sudden end of inflation. In the latter case there is a universal supersymmetric minimum where the scalars end up, preventing the decompactification scenario. The gravitino mass is independent from the inflationary scale with no fine-tuning of the parameters. The observational predictions conform to the universal value of attractors, fully compatible with the Planck data, with possibly a capped number of e-folds due to the interplay with moduli.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2016)·7 citations
25. 25*

    Graviton and gluon scattering from first principles

    Rutger H. Boels🇩🇪 · Ricardo Medina🇧🇷

    Graviton and gluon scattering are studied from minimal physical assumptions such as Poincare and gauge symmetry as well as unitarity. The assumptions lead to an interesting and surprisingly restrictive set of linear equations. This shows gluon and graviton scattering to be related in many field and string theories, explaining and extending several known results. By systematic analysis exceptional graviton scattering amplitudes are derived which in general dimensions can not be related to gluon amplitudes. The simplicity of the formalism guarantees wide further applicability to gauge and gravity theories.

    ↳ hep-thhep-phPRL(2017)·34 citations
26. 26*

    Kinematic sensitivity to the Fierz term of $\beta$-decay differential spectra

    Martin Gonzalez-Alonso🇫🇷 · Oscar Naviliat-Cuncic🇺🇸

    The current most stringent constraints on exotic scalar or tensor couplings in neutron and nuclear $\beta$ decay, involving left-handed neutrinos, are obtained from the Fierz interference term. The sensitivity to this term in a correlation coefficient is usually driven by an energy-averaged kinematic factor that increases monotonically toward smaller values of the $\beta$ endpoint energies. We first point out here that this property does not hold for certain differential observables that are directly sensitive to the Fierz term, such as the $\beta$ or the recoil energy spectrum. This observation is relevant for the selection of sensitive transitions in searches for exotic couplings through spectrum shape measurements. We then point out previous errors in the exploitation of measurements of the $\beta -\nu$ angular correlation coefficient and discuss their impact on the extraction of constraints on exotic couplings.

    ↳ nucl-exhep-phnucl-thPRC(2016)·44 citations
27. 27*

    Emission of neutron-proton and proton-proton pairs in neutrino scattering

    I. Ruiz Simo🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · A. De Pace🇮🇹 · J.A. Caballero🇪🇸 · G.D. Megias🇪🇸 · T.W. Donnelly🇺🇸

    We use a recently developed model of relativistic meson-exchange currents to compute the neutron-proton and proton-proton yields in $({\nu }_{\mu },{\mu }^{-})$ scattering from ${}^{12}$C in the 2p-2h channel. We compute the response functions and cross sections with the relativistic Fermi gas model for different kinematics from intermediate to high momentum transfers. We find a large contribution of neutron-proton configurations in the initial state, as compared to proton-proton pairs. In the case of charge-changing neutrino scattering the 2p-2h cross section of proton-proton emission ({\it i.e.,} np in the initial state) is much larger than for neutron-proton emission ({\it i.e.,} two neutrons in the initial state) by a $(\omega ,q)$-dependent factor. The different emission probabilities of distinct species of nucleon pairs are produced in our model only by meson-exchange currents, mainly by the $\Delta$ isobar current. We also analyze other effects including exchange contributions and the effect of the axial and vector currents.

    ↳ nucl-thhep-phPLB(2016)·45 citations
28. 28*

    Cumulative effects in inflation with ultra-light entropy modes

    Ana Achúcarro🇪🇸 · Vicente Atal🇳🇱 · Cristiano Germani🇪🇸 · Gonzalo A. Palma🇨🇱

    In multi-field inflation one or more non-adiabatic modes may become light, potentially inducing large levels of isocurvature perturbations in the cosmic microwave background. If in addition these light modes are coupled to the adiabatic mode, they influence its evolution on super horizon scales. Here we consider the case in which a non-adiabatic mode becomes approximately massless ("ultralight") while still coupled to the adiabatic mode, a typical situation that arises with pseudo-Nambu-Goldstone bosons or moduli. This ultralight mode freezes on super-horizon scales and acts as a constant source for the curvature perturbation, making it grow linearly in time and effectively suppressing the isocurvature component. We identify a Stuckelberg-like emergent shift symmetry that underlies this behavior. As inflation lasts for many e-folds, the integrated effect of this source enhances the power spectrum of the adiabatic mode, while keeping the non-adiabatic spectrum approximately untouched. In this case, towards the end of inflation all the fluctuations, adiabatic and non-adiabatic, are dominated by a single degree of freedom.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2017)·86 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.