Fri·May 8, 2020Friday·May 8, 2020

1. 01*

   The $SO(10)$-inspired leptogenesis timely opportunity

   Pasquale Di Bari🇬🇧 · Rome Samanta🇬🇧

   We study the connection between absolute neutrino mass and neutrino mixing parameters within $SO(10)$-inspired leptogenesis. We show that current favoured values of the unknown neutrino mixing parameters point toward values of the absolute neutrino mass scale that will be fully tested by cosmological observations and neutrinoless double beta decay experiments during next years. In particular, for $m_{D2}/m_{\mathrm{charm}}\le 5$, where $m_{D2}$ is the intermediate Dirac neutrino mass, and for current best fit values of the Dirac phase $\delta$ and the atmospheric neutrino mixing angle ${\theta }_{23}$, we derive a lower bound on the neutrinoless double beta decay effective neutrino mass $m_{ee}\gtrsim 31\mathrm{meV}$ and on the sum of the neutrino masses ${\sum }_i{m}_i\gtrsim 125\mathrm{meV}$. These lower bounds hold for normally ordered neutrino masses, as currently favoured by global analyses and approximately for $\delta \in [155^{\circ },240^{\circ }]$ and ${\theta }_{23}$ in the second octant. If values in this region will be confirmed by future planned long baseline experiments, then a signal at next generation neutrinoless double beta decay experiments is expected, despite neutrino masses being normally ordered. Outside the region, the lower bounds strongly relax but a great fraction of the allowed range of values still allows a measurement of the lightest neutrino mass. Therefore, in the the next years low energy neutrino experiments will provide a very stringent test of $SO(10)$-inspired leptogenesis, resulting either in severe constraints or in a strong evidence.

   hep-phhep-exJHEP(2020)·18 citations
2. 02*

   The naturalness in the BLMSSM and B-LSSM

   Xing-Xing Dong🇨🇳 · Tai-Fu Feng🇨🇳 · Shu-Min Zhao🇨🇳 · Hai-Bin Zhang🇨🇳

   In order to interpret the Higgs mass and its decays more naturally, we hope to intrude the BLMSSM and B-LSSM. In the both models, the right-handed neutrino superfields are introduced to better explain the neutrino mass problems. In addition, there are other superfields considered to make these models more natural than MSSM. In this paper, the method of ${\chi }^2$ analyses will be adopted in the BLMSSM and B-LSSM to calculate the Higgs mass, Higgs decays and muon $g-2$. With the fine-tuning in the region $0.67\%-2.5\%$ and $0.67\%-5\%$, we can obtain the reasonable theoretical values that are in accordance with the experimental results respectively in the BLMSSM and B-LSSM. Meanwhile, the best-fitted benchmark points in the BLMSSM and B-LSSM will be acquired at minimal $({\chi }_{min}^{BL}{)}^2=2.34736$ and $({\chi }_{min}^{B-L}{)}^2=2.47754$, respectively.

   hep-phEPJC(2020)·4 citations
3. 03*

   Leptogenesis in the $\mu \tau$ basis

   C. C. Nishi🇧🇷 · Chee Sheng Fong🇧🇷

   We formulate three-flavor type-I leptogenesis in the $\mu \tau$ basis which is convenient because in the three-flavor regime, both $\mu$ and $\tau$ charged lepton Yukawa interactions are in thermal equilibrium and the thermal bath is symmetric under the exchange $\mu \leftrightarrow \tau$. We apply this formalism to models with $\mu \tau$-reflection ${\mathsf{CP}}^{\mu \tau }$ symmetry. We confirm the previous result that leptogenesis fails in the three-flavor regime with exact ${\mathsf{CP}}^{\mu \tau }$ symmetry. Allowing ${\mathsf{CP}}^{\mu \tau }$ symmetry to be broken to various degrees, we show that leptogenesis can be successful in the three-flavor regime only in certain tuned parameter space, which could further imply additional symmetry is at play. As a bonus, we derive analytical expressions which could be utilized whenever the branching ratios for the decays to $\mu$ and $\tau$ flavors are equal or approximately so.

   hep-phJHEP(2020)·1 citation
4. 04*

   Anatomy of Higgs decays into $\gamma \gamma$ and $\gamma Z$ within the EChL in the $R_{\xi }$ gauges

   Maria Herrero🇪🇸 · Roberto A. Morales🇪🇸

   In this work we study the Higgs boson decays into two photons and into one photon and one $Z$ gauge boson within the context of the non-linear Effective Field Theory called the Electroweak Chiral Lagrangian. We present a detailed computation of the corresponding amplitudes to one-loop level in the covariant $R_{\xi }$ gauges. We assume that the fermionic loop contributions are as in the Standard Model and focus here just in the computation of the bosonic loop contributions. Our renormalization program and the anatomy of the various contributions participating in the $R_{\xi }$ gauges are fully explored. With this present computation we demonstrate the gauge invariance of the EChL result, not only for the case of on-shell Higgs boson, but also for the most general and interesting case of off-shell Higgs boson. We finally analyse and conclude on the special relevance of the Goldstone boson loops, in good agreement with the expected chiral loops behaviour in Chiral Lagrangians. We perform a systematic comparison with the corresponding computation of the Standard Model in the $R_{\xi }$ gauges and with the previous EChL results in the unitary gauge. This work represents the first computation within the EChL of these Higgs observables to one-loop in the most general $R_{\xi }$ gauges and with a full renormalization program description, not yet fully explored in the previous literature and which is different to the most frequently used in the linear Effective Field Theory (SMEFT).

   hep-phPRD(2020)·25 citations
5. 05*

   Precise WIMP Dark Matter Abundance and Standard Model Thermodynamics

   Ken'ichi Saikawa🇩🇪 · Satoshi Shirai🇯🇵

   A weakly interacting massive particle (WIMP) is a leading candidate of the dark matter. The WIMP dark matter abundance is determined by the freeze-out mechanism. Once we know the property of the WIMP particle such as the mass and interaction, we can predict the dark matter abundance. There are, however, several uncertainties in the estimation of the WIMP dark matter abundance. In this work, we focus on the effect from Standard Model thermodynamics. We revisit the estimation of the WIMP dark matter abundance and its uncertainty due to the equation of state (EOS) in the Standard Model. We adopt the up-to-date estimate of the EOS of the Standard Model in the early Universe and find nearly 10% difference in the 1-1000 GeV dark matter abundance, compared to the conventional estimate of the EOS.

   hep-phastro-ph.COJCAP(2020)·94 citations
6. 06*

   Scalar Dark Matter and Electroweak Stability

   Durmus Demir🇹🇷 · Cem Salih Un🇹🇷

   The standard model of elementary particles (SM), despite experimental completion at the LHC, needs to be extended for various physical reasons, including the cold dark matter (DM). Each extension comes with its scale and mechanism, and typically lifts, at the loop level, the electroweak scale towards its high scale. The problem is to keep the electroweak scale stable while providing a room for the aforementioned heavy extensions. To this end, it turns out that the SM Higgs sector remains stable in the presence of a heavy scalar if their quartic couplings unify at a certain scale when their masses are degenerate. Under this mass-degeneracy-driven unification (MDDU), the scalar under concern is found to qualify as a viable DM candidate and to leave the electroweak scale stable. Our detailed simulation studies explicitly show that the MDDU parameter space agrees with current collider and astrophysical bounds. Our work can be extended to other relevant scalars (like flavons, inflaton and others) as a mechanism by which the electroweak scale is held stable.

   hep-ph6 citations
7. 07*

   Probing Light Gauge Bosons in Tau Neutrino Experiments

   Felix Kling🇺🇸

   The tau neutrino is probably the least studied particle in the SM, with only a handful of interaction events being identified so far. This can in part be attributed to their small production rate in the SM, which occurs mainly through D_s meson decay. However, this also makes the tau neutrino flux measurement an interesting laboratory for additional new physics production modes. In this study, we investigate the possibility of tau neutrino production in the decay of light vector bosons. We consider four scenarios of anomaly-free U(1) gauge groups corresponding to the B-L, B-L_mu-2L_tau, B-L_e-2L_tau and B-3L_tau numbers, analyze current constraints on their parameter spaces and explore the sensitivity of DONuT and as well as the future emulsion detector experiments FASERnu, SND@LHC an SND@SHiP. We find that these experiments provide the leading direct constraints in parts of the parameter space, especially when the vector boson's mass is close to the mass of the omega meson.

   hep-phPRD(2020)·56 citations
8. 08*

   Dark matter stability from Dirac neutrinos in scotogenic 3-3-1-1 theory

   Julio Leite🇧🇷 · América Morales🇲🇽 · José W. F. Valle🇪🇸 · Carlos A. Vaquera-Araujo🇲🇽

   We propose the simplest TeV-scale scotogenic extension of the original 3-3-1 theory, where dark matter stability is linked to the Dirac nature of neutrinos, which results from an unbroken $B-L$ gauge symmetry. The new gauge bosons get masses through the interplay of spontaneous symmetry breaking à la Higgs and the Stueckelberg mechanism.

   hep-phPRD(2020)·22 citations
9. 09*

   Inclusive and effective bulk viscosities in the hadron gas

   J.-B. Rose🇩🇪 · J. M. Torres-Rincon🇩🇪 · H. Elfner🇩🇪

   We estimate the temperature dependence of the bulk viscosity in a relativistic hadron gas. Employing the Green-Kubo formalism in the SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) transport approach, we study different hadronic systems in increasing order of complexity. We analyze the (in)validity of the single exponential relaxation ansatz for the bulk-channel correlation function and the strong influence of the resonances and their lifetimes. We discuss the difference between the inclusive bulk viscosity of an equilibrated, long-lived system, and the effective bulk viscosity of a short-lived mixture like the hadronic phase of relativistic heavy-ion collisions, where the processes whose inverse relaxation rate are larger than the fireball duration are excluded from the analysis. This clarifies the differences between previous approaches which computed the bulk viscosity including/excluding the very slow processes in the hadron gas. We compare our final results with previous hadron gas calculations and confirm a decreasing trend of the inclusive bulk viscosity over entropy density as temperature increases, whereas the effective bulk viscosity to entropy ratio, while being lower than the inclusive one, shows no strong dependence to temperature.

   hep-phnucl-exnucl-thJ.Phys.G(2020)·31 citations
10. 10*

    Safety in darkness: Higgs portal to simple Yukawa systems

    Astrid Eichhorn🇩🇰 · Martin Pauly🇩🇪

    The nature of dark matter and the fundamental quantum structure of spacetime could be directly linked in the asymptotic-safety framework. A toy model for the visible Higgs-Yukawa sector of the Standard Model, coupled to a dark sector through a portal coupling, provides a very first example for a model that simultaneously i) could become asymptotically safe at non-vanishing portal coupling, ii) could feature a strongly enhanced predictive power with calculable values for all interactions and thereby iii) give rise to calculable relations between the masses of the dark particles, their self-interactions, and the portal coupling.

    hep-phgr-qchep-thPLB(2021)·57 citations
11. 11*

    Origin of Sterile Neutrino Dark Matter via Vector Secret Neutrino Interactions

    Kevin J. Kelly🇺🇸 · Manibrata Sen🇺🇸 · Walter Tangarife🇺🇸 · Yue Zhang🇨🇦

    Secret neutrino interactions can play an essential role in the origin of dark matter. We present an anatomy of production mechanisms for sterile neutrino dark matter, a keV-scale gauge-singlet fermion that mixes with active neutrinos, in the presence of a new vector boson mediating secret interactions among active neutrinos. We identify three regimes of the vector boson's mass and coupling where it makes distinct impact on dark matter production through the dispersion relations and/or scattering rates. We also analyze models with gauged $L_{\mu }-L_{\tau }$ and $B-L$ numbers which have a similar dark matter cosmology but different vector boson phenomenology. We derive the parameter space in these models where the observed relic abundance is produced for sterile neutrino dark matter. They serve as well-motivated target for the upcoming experimental searches.

    hep-phastro-ph.COhep-exPRD(2020)·81 citations
12. 12*

    Spinning Black Hole Binary Dynamics, Scattering Amplitudes and Effective Field Theory

    Zvi Bern🇺🇸 · Andres Luna🇺🇸 · Radu Roiban🇺🇸 · Chia-Hsien Shen🇺🇸 · Mao Zeng🇨🇭

    We describe a systematic framework for finding the conservative potential of compact binary systems with spin based on scattering amplitudes of particles of arbitrary spin and effective field theory. An arbitrary-spin formalism is generally required in the classical limit. By matching the tree and one-loop amplitudes of four spinning particles with those of a suitably-chosen effective field theory, we obtain the spin1-spin2 terms of a two-body effective Hamiltonian through O(G^2) and valid to all orders in velocity. Solving Hamilton's equations yields the impulse and spin changes of the individual bodies. We write them in a surprisingly compact form as appropriate derivatives of the eikonal phase obtained from the amplitude. It seems likely this structure persists to higher orders. We also point out various double-copy relations for general spin.

    ↳ hep-thgr-qchep-phPRD(2021)·320 citations
13. 13*

    The Electroweak Sphaleron in a strong magnetic field

    David L.-J. Ho🇬🇧 · Arttu Rajantie🇬🇧

    In an external magnetic field, the energy of the electroweak sphaleron---representing the energy barrier to baryon and lepton number violation---decreases but remains nonzero until the upper Ambjorn-Olesen critical field strength set by the Higgs mass and the electric charge, where it vanishes. We demonstrate this by numerically computing the sphaleron configuration in the presence of an external magnetic field, over the full range of field strengths until the energy barrier vanishes. We discuss the implications for baryogenesis in the early universe, and the possibility of observing of baryon and lepton number violation in heavy-ion collisions.

    ↳ hep-thhep-lathep-phPRD(2020)·18 citations
14. 14*

    Running vacuum in quantum field theory in curved spacetime: renormalizing ${\rho }_{vac}$ without $\sim m^4$ terms

    Cristian Moreno-Pulido🇪🇸 · Joan Sola🇪🇸

    The $\Lambda$-term in Einstein's equations is a fundamental building block of the `concordance' $\Lambda$CDM model of cosmology. Even though the model is not free of fundamental problems, they have not been circumvented by any alternative dark energy proposal either. Here we stick to the $\Lambda$-term, but we contend that it can be a `running quantity' in quantum field theory (QFT) in curved spacetime. A plethora of phenomenological works have shown that this option can be highly competitive with the $\Lambda$CDM with a rigid cosmological term. The, so-called, `running vacuum models' (RVM's) are characterized by the vacuum energy density, ${\rho }_{vac}$, being a series of (even) powers of the Hubble parameter and its time derivatives. Such theoretical form has been motivated by general renormalization group arguments, which look plausible. Here we dwell further upon the origin of the RVM structure within QFT in FLRW spacetime. We compute the renormalized energy-momentum tensor with the help of the adiabatic regularization procedure and find that it leads essentially to the RVM form. This means that ${\rho }_{vac}(H)$ evolves as a constant term plus dynamical components $\mathcal{O}(H^2)$ and $\mathcal{O}(H^4)$, the latter being relevant for the early universe only. However, the renormalized ${\rho }_{vac}(H)$ does not carry dangerous terms proportional to the quartic power of the masses ($\sim m^4$) of the fields, these terms being a well-known source of exceedingly large contributions. At present, ${\rho }_{vac}(H)$ is dominated by the additive constant term accompanied by a mild dynamical component $\sim \nu H^2$ ($|\nu |\ll 1$), which mimics quintessence.

    ↳ gr-qcastro-ph.COhep-phhep-thEPJC(2020)·113 citations
15. 15*

    Finite Z-less integral expressions for $\beta$-functions in the MS4 scheme

    N.D. Lenshina🇷🇺 · A.A. Radionov🇷🇺 · F.V. Tkachov🇷🇺

    The generalized minimal subtraction scheme for ultraviolet renormalization (Kuznetsov and Tkachov, 1988) is fine-tuned with applications in mind. The resulting ${\text{MS}}^4$ scheme obviates extraneous regularizations and renders momentum integrands integrable by subtracting troublesome asymptotic terms in a physically correct fashion due to the use of special minimal subtraction operators defined congruously with the physically natural Polchinski cutoffs. A direct derivation of the Callan-Symanzik equations avoids divergent renormalization factors or counterterms, and automatically yields explicit exact finite integral expressions for renormalization group functions.

    ↳ hep-thhep-phPhys.Part.Nucl.Lett.(2021)·4 citations
16. 16*

    Heavy flavor quenching and flow: the roles of initial condition, pre-equilibrium evolution and in-medium interaction

    Shu-Qing Li🇨🇳 · Wen-Jing Xing🇨🇳 · Feng-Lei Liu🇨🇳 · Shanshan Cao🇺🇸 · Guang-You Qin🇨🇳

    Within an advanced Langevin-hydrodynamics framework coupled to a hybrid fragmentation-coalescence hadronization model, we study heavy flavor quenching and flow in relativistic heavy-ion collisions. We investigate how the initial heavy quark spectrum, the energy loss and hadronization mechanisms of heavy quarks in medium, the evolution profile of pre-equilibrium stage, the flow of medium and the temperature dependence of heavy quark diffusion coefficient influence the suppression and elliptic flow of heavy mesons at RHIC and the LHC. Our result shows that different modeling of initial conditions, pre-equilibrium evolution and in-medium interaction can individually yield about 10-40% uncertainties in D meson suppression and flow at low transverse momentum. We also find that a proper combination of collisional versus radiative energy loss, coalescence versus fragmentation in hadronization, and the inclusion of medium flow are the most important factors for describing the suppression and elliptic flow of heavy mesons.

    ↳ nucl-thhep-phnucl-exCPC(2020)·29 citations
17. 17*

    Exact $\beta$-function in Abelian and non-Abelian $\mathcal{N}=1$ supersymmetric gauge models and its analogy with QCD $\beta$-function in C-scheme

    I. O. Goriachuk🇷🇺 · A. L. Kataev🇷🇺

    For $\mathcal{N}=1$ supersymmetric Yang-Mills theory without matter it is demonstrated that there is a class of renormalization schemes, in which the exact Novikov, Shifman, Vainshtein, and Zakharov (NSVZ) formula for the renormalization group $\beta$-function, defined in terms of the renormalized coupling constant, is valid. These schemes are related with each other by finite renormalizations forming a one-parameter commutative subgroup of general renormalization group transformations. The analogy between the exact $\beta$-function in $\mathcal{N}=1$ supersymmetric Yang-Mills theory without matter and the $\beta$-function of quantum chromodynamics in the C-scheme is discussed.

    ↳ hep-thhep-phPisma Zh.Eksp.Teor.Fiz.(2020)·20 citations
18. 18*

    Phase diagram of helically imbalanced QCD matter

    M. N. Chernodub🇫🇷 · Victor E. Ambrus🇷🇴

    We discuss the influence of a helicity imbalance on the phase diagram of dense QCD at finite temperature. We argue that the helical chemical potential is a thermodynamically relevant quantity in theories with the mass gap generation. Using the linear sigma model coupled to quarks, we show that the presence of the helical density substantially affects the phase diagram of dense quark matter. A moderate helical density makes the chiral phase transition softer while shifting the critical endpoint towards lower temperatures and higher baryon chemical potentials. As the helical density increases, the segment of the first-order transition disappears, and the chiral transition becomes a soft crossover. At even higher helical chemical potentials, the first-order transition reappears again at the zero-density finite-temperature transition and extends into the interior of the phase diagram. This evolution of the chiral transition reflects the existence of a thermodynamic duality between helical and vector (baryonic) chemical potentials. We also show that the presence of the helicity imbalance of quark matter increases the curvature of the chiral pseudocritical line in QCD.

    ↳ hep-thhep-phnucl-thPRD(2021)·15 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.