Mon·Aug 12, 2019Monday·August 12, 2019

1. 01*

   Testing Seesaw and Leptogenesis with Gravitational Waves

   Jeff A. Dror🇺🇸 · Takashi Hiramatsu🇯🇵 · Kazunori Kohri🇯🇵 · Hitoshi Murayama🇺🇸 · Graham White🇨🇦

   We present the possibility that the seesaw mechanism with thermal leptogenesis can be tested using the stochastic gravitational background. Achieving neutrino masses consistent with atmospheric and solar neutrino data, while avoiding non-perturbative couplings, requires right-neutrinos lighter than the typical scale of grand unification. This scale separation suggests a symmetry protecting the right handed neutrinos from getting a mass. Thermal leptogenesis would then require that such a symmetry be broken below the reheating temperature. We enumerate all such possible symmetries consistent with these minimal assumptions and their corresponding defects, finding that in many cases, gravitational waves from the network of cosmic strings should be detectable. Estimating the predicted gravitational wave background we find that future space-borne missions could probe the entire range relevant for thermal leptogenesis.

   hep-phastro-ph.COPRL(2020)·170 citations
2. 02*

   The Hydrogen Bond of QCD in Doubly Heavy Baryons and Tetraquarks

   L. Maiani🇮🇹 · A.D. Polosa🇮🇹 · V. Riquer🇮🇹

   In this paper we present in greater detail previous work on the Born-Oppenheimer approximation to treat the hydrogen bond of QCD, and add a similar treatment of doubly heavy baryons. Doubly heavy exotic resonances X and Z can be described as color molecules of two-quark lumps, the analogue of the H_2 molecule, and doubly heavy baryons as the analog of the H_2^+ ion, except that the two heavy quarks attract each other. We compare our results with constituent quark model and lattice QCD calculations and find further evidence in support of this upgraded picture of compact tetraquarks and baryons.

   hep-phPRD(2019)·53 citations
3. 03*

   Observing Dirac neutrinos in the cosmic microwave background

   Kevork N. Abazajian🇺🇸 · Julian Heeck🇺🇸

   Planned CMB Stage IV experiments have the potential to measure the effective number of relativistic degrees of freedom in the early Universe, $N_{\text{eff}}$, with percent-level accuracy. This probes new thermalized light particles and also constrains possible new-physics interactions of Dirac neutrinos. Many Dirac-neutrino models that aim to address the Dirac stability, the smallness of neutrino masses or the matter--anti-matter asymmetry of our Universe endow the right-handed chirality partners ${\nu }_R$ with additional interactions that can thermalize them. Unless the reheating temperature of our Universe was low, this leads to testable deviations in $N_{\text{eff}}$. We discuss well-motivated models for ${\nu }_R$ interactions such as gauged $U(1{)}_{B-L}$ and the neutrinophilic two-Higgs-doublet model, and compare the sensitivity of SPT-3G, Simons Observatory, and CMB-S4 to other experiments, in particular the LHC.

   hep-phastro-ph.COPRD(2019)·93 citations
4. 04*

   Short-distance constraints for the HLbL contribution to the muon anomalous magnetic moment

   Johan Bijnens🇸🇪 · Nils Hermansson-Truedsson🇸🇪 · Antonio Rodríguez-Sánchez (Lund)🇸🇪

   We derive short-distance constraints for the hadronic light-by-light contribution (HLbL) to the anomalous magnetic moment of the muon in the kinematic region where the three virtual momenta are all large. We include the external soft photon via an external field leading to a well-defined Operator Product Expansion. We establish that the perturbative quark loop gives the leading contribution in a well defined expansion. We compute the first nonzero power correction. It is related to to the magnetic susceptibility of the QCD vacuum. The results can be used as model-independent short-distance constraints for the very many different approaches to the HLbL contribution. Numerically the power correction is found to be small.

   hep-phPLB(2019)·437 citations
5. 05*

   Fitting in or odd one out? Pulls vs residual responses in $b\to s{\ell }^{+}{\ell }^{-}$

   Bernat Capdevila🇪🇸 · Ursula Laa🇦🇺 · German Valencia🇦🇺

   New results in processes with an underlying quark transition $b\to s{\ell }^{+}{\ell }^{-}$ have been recently reported by the LHCb and Belle II collaborations. In this note we show how the main implications of a handful of new measurements can be understood with the tools introduced in our recent paper, arXiv:1811.10793, without the need to redo the global fits. We find that the main impact of the new results, due to $R_K^{[1.1,6]}$ from LHCb, is a decrease in $C_{10\mu }^{NP}$ with a reduced uncertainty. We validate this conclusion by presenting the result of a new global fit.

   hep-phhep-exphysics.data-an6 citations
6. 06*

   Open-source QCD analysis of nuclear parton distribution functions at NLO and NNLO

   Marina Walt🇩🇪 · Ilkka Helenius🇫🇮 · Werner Vogelsang🇩🇪

   We present new sets of nuclear parton distribution functions (nPDFs) at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO). Our analyses are based on deeply inelastic scattering data with charged-lepton and neutrino beams on nuclear targets. In addition, a set of proton baseline PDFs is fitted within the same framework with the same theoretical assumptions. The results of this global QCD analysis are compared to existing nPDF sets and to the fitted cross sections. Also, the uncertainties resulting from the limited constraining power of the included experimental data are presented. The published work is based on an open-source tool, xFitter, which has been modified to be applicable also for a nuclear PDF analysis. The required extensions of the code are discussed as well.

   hep-phPRD(2019)·69 citations
7. 07*

   Signs for the onset of gluon saturation in exclusive photo-production of vector mesons

   Martin Hentschinski🇲🇽 · Krzysztof Kutak🇵🇱

   We investigate the energy dependence of the photo-production cross-section of vector mesons $J/\Psi$ and ${\rm Y}$, measured by both HERA experiments H1 and ZEUS in electron-proton collisions and by LHC experiments ALICE, CMS and LHCb in ultra-peripheral proton-proton and ultra-peripheral proton-lead collisions. Our study uses 2 particular fits of inclusive unintegrated gluon distribution, based on non-linear Balitsky-Kovchegov evolution (Kutak-Sapeta gluon; KS) and next-to-leading order Balitsky-Fadin-Kuraev-Lipatov evolution (Hentschinski-Sabio Vera-Salas gluon; HSS). We find that linear next-to-leading order BFKL evolution can only describe production at highest energies, if perturbative corrections are increased to unnaturally large values; rendering this corrections small, the growth with energy is too strong in the LHC region and the description of $J/\Psi$ data fails. For the KS gluon we find that an accurate description of $J/\Psi$ data is possible if non-linear corrections to low x QCD evolution are taken into account; without such correction a description of data fails. We interpret this observation as a clear signal for the presence of high gluon densities in low x the proton, characteristic for the onset of gluon saturation.

   hep-phPoS(2019)·2 citations
8. 08*

   Entanglement and collective flavor oscillations in a dense neutrino gas

   Michael J. Cervia🇺🇸 · Amol V. Patwardhan🇺🇸 · A. B. Balantekin🇺🇸 · S. N. Coppersmith🇺🇸 · Calvin W. Johnson🇺🇸

   We investigate the importance of going beyond the mean-field approximation in the dynamics of collective neutrino oscillations. To expand our understanding of the coherent neutrino oscillation problem, we apply concepts from many-body physics and quantum information theory. Specifically, we use measures of nontrivial correlations (otherwise known as "entanglement") between the constituent neutrinos of the many-body system, such as the entanglement entropy and the Bloch vector of the reduced density matrix. The relevance of going beyond the mean field is demonstrated by comparisons between the evolution of the neutrino state in the many-body picture vs the mean-field limit, for different initial conditions.

   hep-phastro-ph.HEnucl-thquant-phPRD(2019)·83 citations
9. 09*

   Molecular Interpretation of the $P_c(4440)$ and $P_c(4457)$ States

   T.J. Burns🇬🇧 · E.S. Swanson🇺🇸

   A molecular model of the $P_c(4457)$ and $P_c(4440)$ LHCb states is proposed. The model relies on channels coupled by long range pion-exchange dynamics with features that depend crucially on the novel addition of the ${\Lambda }_c(2595)\bar{D}$ channel. A striking prediction of the model is the unusual combination of quantum numbers $J^P(4457)=1/2^{+}$ and $J^P(4440)=3/2^{-}$. Unlike in other models, a simultaneous description of both states is achieved without introducing additional short-range interactions. The model also gives a natural explanation for the relative widths of the states. We show that the usual molecular scenarios cannot explain the production rate of $P_c$ states in ${\Lambda }_b$ decays, and that this can be resolved by including ${\Lambda }_c(2595)\bar{D}$ and related channels. Experimental tests and other states are discussed in the conclusions.

   hep-phPRD(2019)·113 citations
10. 10*

    Functional renormalization group approach to color superconducting phase transition

    G. Fejos🇯🇵 · N. Yamamoto🇯🇵

    We investigate the order of the color superconducting phase transition using the functional renormalization group approach. We analyze the Ginzburg-Landau effective theory of color superconductivity and more generic scalar $SU(N_c)$ gauge theories by calculating the $\beta$ function of the gauge coupling in arbitrary dimension $d$ based on two different regularization schemes. We find that in $d=3$, due to gluon fluctuation effects, the $\beta$ function never admits an infrared fixed point solution. This indicates that, unlike the ordinary superconducting transition, color superconductivity can only show a first-order phase transition.

    hep-phcond-mat.supr-conhep-thJHEP(2019)·5 citations
11. 11*

    Freeze-Twin Dark Matter

    Seth Koren🇺🇸 · Robert McGehee🇺🇸

    The mirror twin Higgs (MTH) addresses the little hierarchy problem by relating every Standard Model (SM) particle to a twin copy, but is in tension with cosmological bounds on light degrees of freedom. Asymmetric reheating has recently been proposed as a simple way to fix MTH cosmology by diluting the twin energy density. We show that this dilution sets the stage for an interesting freeze-in scenario where both the initial absence of dark sector energy and the feeble coupling to the SM are motivated for reasons unrelated to dark matter production. We give the twin photon a Stueckelberg mass and freeze-in twin electron and positron dark matter through the kinetic mixing portal. The kinetic mixing required to obtain the dark matter abundance is of the loop-suppressed order expected from infrared contributions in the MTH.

    hep-phPRD(2020)·88 citations
12. 12*

    Non-perturbative Effects and Unparticle Physics in Generalized Schwinger Models

    Howard Georgi🇺🇸 · Bea Noether

    We analyze generalizations of the Schwinger model with more massless fermions and more vector fields. We focus on models with the gauge structure of ``diagonal color $SU(n)$'' but unlike previous investigators, we do not assume that all the gauge boson masses are the same. Unlike the Schwinger model, these are Banks-Zaks models with conformal sectors that survive at long distances. In addition to local operators that go to ``unparticle operators'' with non-zero anomalous dimensions at long distances, they contain local operators like the ${\bar{\psi }}_L{\psi }_R$ operator in the Schwinger model which go to constants at long distances. These operators have calculable vacuum expectation values (up to phases). Cluster decomposition applied to correlation functions involving these operators yields nontrivial and calculable non-perturbative constraints on correlation functions. One consequence is ``conformal coalescence'' in which linear combinations of short distance operators disappear from the long-distance theory, leaving only one kind of unparticle stuff in the low-energy theory. We believe that our detailed analysis of diagonal color $SU(n)$ paints an appealing picture of unparticle operators as the result of an incomplete binding of the massless fermions. We complete the picture (and the binding) by analyzing the diagonal color $U(n)$ model with a very small $U(1)$ coupling and thus a gauge boson with a dynamical mass much smaller than the other masses in the model. This model has a mass gap and we can see explicitly the transition from free-fermion behavior at short distances to unparticle physics at intermediate distances to the physics of massive particles at long distances.

    ↳ hep-thhep-ph11 citations
13. 13*

    Measurement of ${\mathbf{q}}_{\mathbf{T}}$-weighted transverse-spin-dependent azimuthal asymmetries at COMPASS

    Riccardo Longo🇺🇸

    COMPASS is a fixed-target experiment in operation at the CERN North Area (SPS, M2 beam-line) since 2002. An important part of the broad physics programme of the experiment is dedicated to the exploration of the transverse spin-structure of the nucleon studying target transverse spin dependent azimuthal asymmetries (TSAs) arising in the Semi-Inclusive DIS (SIDIS) and Drell-Yan (DY) cross-sections. In addition to those measurements, COMPASS has recently studied also the TSAs weighted by powers of the hadron transverse momentum (in SIDIS) and virtual photon transverse momentum, $q_T$ (in DY). In the transverse momentum dependent (TMD) QCD approach, the conventional DY TSAs are interpreted as convolutions of the beam pion and of the transversely polarized target proton TMD parton distribution functions (PDFs), while the $q_T$-weighted TSAs can be interpreted as simple products of transverse moments of the TMD PDFs. In 2015 and 2018 COMPASS performed two years of Drell-Yan data taking with a 190 GeV/$c$ ${\pi }^{-}$ beam impinging on a transversely polarized NH${}_3$ target. The analysis of the $q_T$-weighted TSAs performed on these two data sets is presented in this paper. The results for DY Sivers $q_T$ weighted TSA are compared with the expectations based on the studies of the weighted Sivers asymmetry measured in the SIDIS process. Combining the information from SIDIS and DY measurements, the pion Boer-Mulders TMD PDF is also studied.

    ↳ hep-exhep-phPoS(2019)·5 citations
14. 14*

    First direct detection constraint on mirror dark matter kinetic mixing using LUX 2013 data

    LUX Collaboration: D. S. Akerib🇺🇸 · S. Alsum🇺🇸 · H. M. Araújo🇬🇧 · X. Bai🇺🇸 · J. Balajthy🇺🇸 · A. Baxter🇬🇧 · E. P. Bernard🇺🇸 · A. Bernstein🇺🇸 · T. P. Biesiadzinski🇺🇸 · E. M. Boulton🇺🇸 · B. Boxer🇬🇧 · P. Brás🇵🇹 and 87 other authors

    We present the results of a direct detection search for mirror dark matter interactions, using data collected from the Large Underground Xenon experiment during 2013, with an exposure of 95 live-days $\times$ 118 kg. Here, the calculations of the mirror electron scattering rate in liquid xenon take into account the shielding effects from mirror dark matter captured within the Earth. Annual and diurnal modulation of the dark matter flux and atomic shell effects in xenon are also accounted for. Having found no evidence for an electron recoil signal induced by mirror dark matter interactions we place an upper limit on the kinetic mixing parameter over a range of local mirror electron temperatures between 0.1 and 0.6 keV. This limit shows significant improvement over the previous experimental constraint from orthopositronium decays and significantly reduces the allowed parameter space for the model. We exclude mirror electron temperatures above 0.3 keV at a 90% confidence level, for this model, and constrain the kinetic mixing below this temperature.

    ↳ hep-exhep-phPRD(2020)·28 citations
15. 15*

    The scaling density of axion strings

    Mark Hindmarsh🇫🇮 · Joanes Lizarraga🇪🇸 · Asier Lopez-Eiguren🇫🇮 · Jon Urrestilla🇪🇸

    In the QCD axion dark matter scenario with post-inflationary Peccei-Quinn symmetry breaking, the number density of axions, and hence the dark matter density, depends on the length of string per unit volume at cosmic time $t$, by convention written $\zeta /t^2$. The expectation has been that the dimensionless parameter $\zeta$ tends to a constant ${\zeta }_0$, a feature of a string network known as scaling. It has recently been claimed that in larger numerical simulations $\zeta$ shows a logarithmic increase with time, while theoretical modelling suggests an inverse logarithmic correction. Either case would result in a large enhancement of the string density at the QCD transition, and a substantial revision to the axion mass required for the axion to constitute all of the dark matter. With a set of new simulations of global strings we compare the standard scaling (constant-$\zeta$) model to the logarithmic growth and inverse-logarithmic correction models. In the standard scaling model, by fitting to linear growth in the mean string separation $\xi =t/\sqrt{\zeta }$, we find ${\zeta }_0=1.19\pm 0.20$. We conclude that the apparent corrections to $\zeta$ are artefacts of the initial conditions, rather than a property of the scaling network. The residuals from the constant-$\zeta$ (linear $\xi$) fit also show no evidence for logarithmic growth, restoring confidence that numerical simulations can be simply extrapolated from the Peccei-Quinn symmetry-breaking scale to the QCD scale. Re-analysis of previous work on the axion number density suggests that recent estimates of the axion dark matter mass in the post-inflationary symmetry-breaking scenario we study should be increased by about 50%.

    ↳ astro-ph.COhep-phhep-thPRL(2020)·115 citations
16. 16*

    Influence of correlations between yields on the chemical freeze-out temperature

    Dariusz Prorok🇵🇱

    A statistical (thermal) model is applied to the description of hadron yields measured at central nucleus-nucleus collisions at the top RHIC energy $\sqrt{s_{NN}}=200$ GeV and the LHC energy $\sqrt{s_{NN}}=2.76$ TeV. In contrast to the previous analyzes a more general form of the least squares test statistic is used, which takes into account also possible correlations between different species of yields. In addition to hadrons also light nuclei are included in the fits. Because of the lack of data, a toy model is constructed where the correlation coefficients are just free parameters. Because of this the presented considerations are speculative and should be treated as an imperfect illustration of the problem. Within these limitations it is impossible to formulate any definite conclusion, it might be only mentioned that for the considered examples the dependence of the freeze-out temperature and baryon chemical potential on correlations turned out to be weak.

    ↳ nucl-thhep-exhep-phnucl-exChin.J.Phys.(2021)·0 citations
17. 17*

    Axion Quark Nugget Dark Matter: Time Modulations and Amplifications

    Xunyu Liang🇨🇦 · Alexander Mead🇨🇦 · Md Shahriar Rahim Siddiqui🇨🇦 · Ludovic Van Waerbeke🇨🇦 · Ariel Zhitnitsky🇨🇦

    We study the new mechanism of the axion production suggested recently in [1,2]. This mechanism is based on the so-called Axion Quark Nugget (AQN) dark matter model, which was originally invented to explain the similarity of the dark and visible cosmological matter densities. We perform numerical simulations to evaluate the axion flux on the Earth's surface. We examine annual and daily modulations, which have been studied previously and are known to occur for any type of dark matter. We also discuss a novel type of short time enhancements which are unique to the AQN model: the statistical fluctuations and burst-like amplification, both of which can drastically amplify the axion signal, up to a factor $\sim 10^2-10^3$ for a very short period of time. The present work studies the AQN-induced axions within the mass window $10^{-6}\mathrm{eV}\lesssim m_a\lesssim 10^{-3}\mathrm{eV}$ with typical velocities $⟨v_a⟩\sim 0.6c$. We also comment on the broadband detection strategy to search for such relativistic axions by studying the daily and annual time modulations as well as random burst-like amplifications.

    ↳ astro-ph.COhep-phPRD(2020)·22 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.