Wed·Jul 12, 2017Wednesday·July 12, 2017

1. 01*

   Higgs data does not rule out a sequential fourth generation with an extended scalar sector

   Dipankar Das🇮🇳 · Anirban Kundu🇮🇳 · Ipsita Saha🇮🇹

   Contrary to the common perception, we show that the current Higgs data does not eliminate the possibility of a sequential fourth generation that get their masses through the same Higgs mechanism as the first three generations. The inability to fix the sign of the bottom-quark Yukawa coupling from the available data plays a crucial role in accommodating a chiral fourth generation which is consistent with the bounds on the Higgs signal strengths. We show that effects of such a fourth generation can remain completely hidden not only in the production of the Higgs boson through gluon fusion but also to its subsequent decay to $\gamma \gamma$ and $Z\gamma$. This, however, is feasible only if the scalar sector of the Standard Model is extended. We also provide a practical example illustrating how our general prescription can be embedded in a realistic model.

   hep-phPRD(2018)·33 citations
2. 02*

   G-parity breaking in ${\tau }^{-}\to {\eta }^{(\prime )}{\pi }^{-}{\nu }_{\tau }$ decays induced by the ${\eta }^{(\prime )}\gamma \gamma$ form factor

   G. Hernández-Tomé🇲🇽 · G. López Castro🇲🇽 · P. Roig🇲🇽

   Breaking of G-parity or new weak (second class) currents can be responsible for ${\tau }^{-}\to {\eta }^{(\prime )}{\pi }^{-}{\nu }_{\tau }$ decays. Forthcoming measurements of $\tau$ lepton properties at the Belle II experiment will be able to measure this decay channel for the first time. Isolating new physics contributions from the measured rates will require a careful evaluation of G-parity breaking contributions. Here we evaluate the one-loop contribution to ${\tau }^{-}\to {\eta }^{(\prime )}{\pi }^{-}{\nu }_{\tau }$ decays induced by the emission of two virtual photons and its later conversion into an ${\eta }^{(\prime )}$ meson. As expected, this contribution is very small and may be relevant only for new physics searches contributing at the $10^{-4}$ level to the decay rate of ${\tau }^{-}\to {\eta }^{(\prime )}{\pi }^{-}{\nu }_{\tau }$ .

   hep-phPRD(2017)·14 citations
3. 03*

   Exploring Fermionic Dark Matter via Higgs Boson Precision Measurements at the Circular Electron Positron Collider

   Qian-Fei Xiang🇨🇳 · Xiao-Jun Bi🇨🇳 · Peng-Fei Yin🇨🇳 · Zhao-Huan Yu🇦🇺

   We study the impact of fermionic dark matter (DM) on projected Higgs precision measurements at the Circular Electron Positron Collider (CEPC), including the one-loop effects on the $e^{+}{e}^{-}\to Zh$ cross section and the Higgs boson diphoton decay, as well as the tree-level effects on the Higgs boson invisible decay. As illuminating examples, we discuss two UV-complete DM models, whose dark sector contains electroweak multiplets that interact with the Higgs boson via Yukawa couplings. The CEPC sensitivity to these models and current constraints from DM detection and collider experiments are investigated. We find that there exist some parameter regions where the Higgs measurements at the CEPC will be complementary to current DM searches.

   hep-phPRD(2018)·37 citations
4. 04*

   Naturalness and a light $Z^{\prime }$

   Bin Zhu🇨🇳 · Florian Staub🇩🇪 · Ran Ding🇨🇳

   Models with a light, additional gauge boson are attractive extensions of the standard model. Often these models are only considered as effective low energy theory without any assumption about an UV completion. This leaves not only the hierarchy problem of the SM unsolved, but introduces a copy of it because of the new fundamental scalars responsible for breaking the new gauge group. A possible solution is to embed these models into a supersymmetric framework. However, this gives rise to an additional source of fine-tuning compared to the MSSM and poses the question how natural such a setup is. One might expect that the additional fine-tuning is huge, namely, $O(M_{\mathrm{SUSY}}^2/m_{Z^{\prime }}^2)$. In this paper we point out that this is not necessarily the case. We show that it is possible to find a focus point behaviour also in the new sector in co-existence to the MSSM focus point. We call this 'Double Focus Point Supersymmetry'. Moreover, we stress the need for a proper inclusion of radiative corrections in the fine-tuning calculation: a tree-level estimate would lead to predictions for the tuning which can be wrong by many orders of magnitude. As showcase, we use the $U(1{)}_{B-L}$ extended MSSM and discuss possible consequence of the observed ${}^8\text{Be}$ anomaly. However, similar features are expected for other models with an extended gauge group which involve potentially large Yukawa-like interactions of the new scalars.

   hep-phPRD(2017)·7 citations
5. 05*

   On the Renormalizability of Quasi Parton Distribution Functions

   Tomomi Ishikawa🇨🇳 · Yan-Qing Ma🇨🇳 · Jian-Wei Qiu🇺🇸 · Shinsuke Yoshida🇺🇸

   Quasi-parton distribution functions have received a lot of attentions in both perturbative QCD and lattice QCD communities in recent years because they not only carry good information on the parton distribution functions, but also could be evaluated by lattice QCD simulations. However, unlike the parton distribution functions, the quasi-parton distribution functions have perturbative ultraviolet power divergences because they are not defined by twist-2 operators. In this paper, we identify all sources of ultraviolet divergences for the quasi-parton distribution functions in coordinate-space, and demonstrate that power divergences, as well as all logarithmic divergences can be renormalized multiplicatively to all orders in QCD perturbation theory.

   hep-phhep-latPRD(2017)·196 citations
6. 06*

   Gravitational waves from bubble dynamics: Beyond the Envelope

   Ryusuke Jinno🇰🇷 · Masahiro Takimoto🇯🇵

   We study gravitational-wave production from bubble dynamics (bubble collisions and sound waves) during a cosmic first-order phase transition with an analytic approach. We first propose modeling the system with the thin-wall approximation but without the envelope approximation often adopted in the literature, in order to take bubble propagation after collisions into account. The bubble walls in our setup are considered as modeling the scalar field configuration and/or the bulk motion of the fluid. We next write down analytic expressions for the gravitational-wave spectrum, and evaluate them with numerical methods. It is found that, in the long-lasting limit of the collided bubble walls, the spectrum grows from $\propto f^3$ to $\propto f^1$ in low frequencies, showing a significant enhancement compared to the one with the envelope approximation. It is also found that the spectrum saturates in the same limit, indicating a decrease in the correlation of the energy-momentum tensor at late times. We also discuss the implications of our results to gravitational-wave production both from bubble collisions (scalar dynamics) and sound waves (fluid dynamics).

   hep-phastro-ph.COgr-qchep-thJCAP(2019)·192 citations
7. 07*

   Masses and Mixing of Neutral Leptons in a Grand Unified E_6 Model with Intermediate Pati-Salam Symmetry

   Secil Benli🇹🇷 · Tekin Dereli🇹🇷

   A brief review of the assignment of elementary fermions and bosons to irreducible multiplets in grand unified $E_6$ models is followed by a discussion of different, hierarchical symmetry breaking chains from $E_6$ down to $SU(3{)}_C\times U(1{)}_{EM}$. We concentrate here on a model with an intermediate Pati-Salam symmetry for which $(B-L)$ is conserved. In particular, the mass/mixing matrix of electrically neutral fermions (i.e.neutrinos) that would be derived from Yukawa couplings is constructed. The pattern of neutrino masses and some bounds on mixing parameters are discussed.

   hep-phInt.J.Theor.Phys.(2018)·5 citations
8. 08*

   Penguin $b\to s{\ell }^{\prime +}{\ell }^{\prime -}$ and $B$-meson anomalies in a gauged $L_{\mu }-L_{\tau }$

   Chuan-Hung Chen🇹🇼 · Takaaki Nomura🇰🇷

   The $Z^{\prime }$-gauge boson in an $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge symmetry has two interesting features: one is its vector couplings to the charged leptons, and the other is the decoupling from the electron. Based on these properties, we investigate the feasibility to simultaneously resolve the $R_{K^{(\ast )}}=BR(B\to K^{(\ast )}{\mu }^{+}{\mu }^{-})/BR(B\to K^{(\ast )}{e}^{+}{e}^{-})$ and $R_{D^{(\ast )}}=BR(\bar{B}\to D^{(\ast )}\tau {\bar{\nu }}_{\tau })/BR(\bar{B}\to D^{(\ast )}\ell {\bar{\nu }}_{\ell })$ anomalies in an $U(1{)}_{L_{\mu }-L_{\tau }}$ model, where the former is expected to arise from the $Z^{\prime }$-penguin-induced $b\to s{\mu }^{+}{\mu }^{-}$ process and the latter from the tree-level $b\to c\tau {\bar{\nu }}_{\tau }$ decay. In order to achieve the intended purpose, we employ one vector-like doublet lepton and one singlet scalar leptoquark (LQ), in which the new particles all carry the $U(1{)}_{L_{\mu }-L_{\tau }}$ charges; the $b\to s{Z}^{\prime }$ effective interaction is generated from the vector-like lepton and LQ loop, and the $b\to c\tau {\bar{\nu }}_{\tau }$ decay is induced from the LQ. When the constraints from the $b\to s\gamma$, $B^{+}\to K^{+}\nu \bar{\nu }$, $B_c^{-}\to \tau {\bar{\nu }}_{\tau }$, $\Delta F=2$, and $\tau \to \mu \ell \bar{\ell }$ processes are included, it is found that $R_D$ and $R_{D^{\ast }}$ can be enhanced to fit the experimental data, and the Wilson coefficient $C_9$ from the LQ-loop can reach $C_9^{LQ,\mu }\sim -1$, which can explain the $R_K$ and $R_{K^{\ast }}$ anomalies. In addition, in this simple model, the Higgs lepton-flavor violating $h\to \mu \tau$ decay can occur at the tree level, and its branching ratio can be as large as the current experimental upper limit.

   hep-phhep-exPLB(2018)·58 citations
9. 09*

   Centrality dependence of charmed-meson photoproduction in ultrarelativistic heavy ion collisions

   Gong-Ming Yu🇨🇳 · Yan-Bing Cai🇨🇳 · Zhen Bai🇨🇳 · Qiang Hu🇨🇳 · Jian-Song Wang🇨🇳

   We calculate the centrality dependence of inclusive cross section of large-pT charmed-meson ($D^0$, $D^{\ast }$, $D^{\ast +}$, and $D_s^{+}$) from heavy quark fragmentation by the hard photoproduction processes for the nucleus-nucleus collisions in ultrarelativistic heavy ion collisions. The numerical results indicate that the modification of the hard photoproduction processes cannot be negligible for the charmed-meson production in Au-Au collisions at Relativistic Heavy Ion Collider (RHIC) and Pb-Pb collisions at Large Hadron Collider (LHC).

   hep-phnucl-thCommun.Theor.Phys.(2019)·1 citation
10. 10*

    Generalized Heisenberg-Euler formula in Abelian gauge theory with parity violation

    Kimiko Yamashita🇯🇵 · Xing Fan🇺🇸 · Shusei Kamioka🇯🇵 · Shoji Asai🇯🇵 · Akio Sugamoto🇯🇵

    A generalized Heisenberg-Euler formula is given for an Abelian gauge theory having vector as well as axial vector couplings to a massive fermion. So, the formula is applicable to a parity-violating theory. The gauge group is chosen to be $U(1)$. The formula is quite similar to that in quantum electrodynamics, but there is a complexity in which one factor (related to spin) is expressed in terms of the expectation value. The expectation value is evaluated by the contraction with the one-dimensional propagator in a given background field. The formula affords a basis to the vacuum magnetic birefringence experiment, which aims to probe the dark sector, where the interactions of the light fermions with the gauge fields are not necessarily parity conserving.

    hep-phhep-thPTEP(2017)·7 citations
11. 11*

    Cobimaximal Neutrino Mixing from $S_3\times Z_2$

    Ernest Ma (UC Riverside & JCIAS, HKUST)🇺🇸

    It has recently been shown that the phenomenologically successful pattern of cobimaximal neutrino mixing (${\theta }_{13}\ne 0$, ${\theta }_{23}=\pi /4$, and ${\delta }_{CP}=\pm \pi /2$) may be achieved in the context of the non-Abelian discrete symmetry $A_4$. In this paper, the same goal is achieved with $S_3\times Z_2$. The residual lepton $Z_3$ triality in the case of $A_4$ is replaced here by $Z_2\times Z_2$. The associated phenomenology of the scalar sector is discussed.

    hep-phPLB(2018)·30 citations
12. 12*

    Higgs-Precision Constraints on Colored Naturalness

    Rouven Essig🇺🇸 · Patrick Meade🇺🇸 · Harikrishnan Ramani🇺🇸 · Yi-Ming Zhong🇺🇸

    The presence of weak-scale colored top partners is among the simplest solutions to the Higgs hierarchy problem and allows for a natural electroweak scale. We examine the constraints on generic colored top partners coming solely from their effect on the production and decay rates of the observed Higgs with a mass of 125 GeV. We use the latest Higgs precision data from the Tevatron and the LHC as of EPS 2017 to derive the current limits on spin-0, spin-1/2, and spin-1 colored top partners. We also investigate the expected sensitivity from the Run 3 and Run 4 of the LHC, as well from possible future electron-positron and proton-proton colliders, including the ILC, CEPC, FCC-ee, and FCC-hh. We discuss constraints on top partners in the Minimal Supersymmetric Standard Model and Little Higgs theories. We also consider various model-building aspects--multiple top partners, modified couplings between the Higgs and Standard-Model particles, and non-Standard-Model Higgs sectors--and evaluate how these weaken the current limits and expected sensitivities. By modifying other Standard-Model Higgs couplings, we find that the best way to hide low-mass top partners from current data is through modifications of the top-Yukawa coupling, although future measurements of top-quark-pair production in association with a Higgs will extensively probe this possibility. We also demonstrate that models with multiple top partners can generically avoid current and future Higgs precision measurements. Nevertheless, some of the model parameter space can be probed with precision measurements at future electron-positron colliders of, for example, the e+ e- -> Zh cross section.

    hep-phhep-exJHEP(2017)·17 citations
13. 13*

    $D$-wave heavy baryons of the $SU(3)$ flavor $6_F$

    Qiang Mao🇨🇳 · Hua-Xing Chen🇨🇳 · Atsushi Hosaka🇯🇵 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

    We use the method of QCD sum rules to study the $D$-wave charmed and bottom baryons of the $SU(3)$ flavor $6_F$, and calculate their masses up to the order $\mathcal{O}(1/m_Q)$ with $m_Q$ the heavy quark mass. Our results suggest that the ${\Xi }_c(3123)$ can be well interpreted as a $D$-wave ${\Xi }_c^{\prime }(6_F)$ state, and it probably has a partner state close to it. Our results also suggest that there may exist as many as four $D$-wave ${\Omega }_c$ states in the energy region $3.3\sim 3.5$ GeV, and we propose to search for them in the further LHCb and BelleII experiments.

    hep-phhep-exhep-latPRD(2017)·46 citations
14. 14*

    The gravitational waves from the first-order phase transition with a dimension-six operator

    Rong-Gen Cai🇨🇳 · Misao Sasaki🇯🇵 · Shao-Jiang Wang🇨🇳

    We investigate in details the gravitational wave (GW) from the first-order phase transition (PT) in the extended standard model of particle physics with a dimension-six operator, which is capable of exhibiting the recently discovered slow first-order PT in addition to the usually studied fast first-order PT. To simplify the discussion, it is sufficient to work with an example of a toy model with the sextic term, and we propose an unified description for both slow and fast first-order PTs. We next study the full one-loop effective potential of the model with fixed/running renormalization-group (RG) scales. Compared to the prediction of GW energy density spectrum from the fixed RG scale, we find that the presence of running RG scale could amplify the peak amplitude by amount of one order of magnitude while shift the peak frequency to the lower frequency regime, and the promising regime of detection within the sensitivity ranges of various space-based GW detectors shrinks down to a lower cut-off value of the sextic term rather than the previous expectation.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2017)·105 citations
15. 15*

    Strange and charm HVP contributions to the muon ($g-2)$ including QED corrections with twisted-mass fermions

    D. Giusti🇮🇹 · V. Lubicz🇮🇹 · G. Martinelli🇮🇹 · F. Sanfilippo🇮🇹 · S. Simula🇮🇹

    We present a lattice calculation of the Hadronic Vacuum Polarization (HVP) contribution of the strange and charm quarks to the anomalous magnetic moment of the muon including leading-order electromagnetic corrections. We employ the gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with $N_f=2+1+1$ dynamical quarks at three values of the lattice spacing ($a\simeq 0.062,0.082,0.089$ fm) with pion masses in the range $M_{\pi }\simeq 210-450$ MeV. The strange and charm quark masses are tuned at their physical values. Neglecting disconnected diagrams and after the extrapolations to the physical pion mass and to the continuum limit we obtain: $a_{\mu }^s({\alpha }_{em}^2)=(53.1\pm 2.5)\cdot 10^{-10}$, $a_{\mu }^s({\alpha }_{em}^3)=(-0.018\pm 0.011)\cdot 10^{-10}$ and $a_{\mu }^c({\alpha }_{em}^2)=(14.75\pm 0.56)\cdot 10^{-10}$, $a_{\mu }^c({\alpha }_{em}^3)=(-0.030\pm 0.013)\cdot 10^{-10}$ for the strange and charm contributions, respectively.

    ↳ hep-lathep-phJHEP(2017)·62 citations
16. 16*

    The observational evidence for horizons: from echoes to precision gravitational-wave physics

    Vitor Cardoso🇵🇹 · Paolo Pani🇮🇹

    The existence of black holes and of spacetime singularities is a fundamental issue in science. Despite this, observations supporting their existence are scarce, and their interpretation unclear. We overview how strong a case for black holes has been made in the last few decades, and how well observations adjust to this paradigm. Unsurprisingly, we conclude that observational evidence for black holes is impossible to come by. However, just like Popper's black swan, alternatives can be ruled out or confirmed to exist with a single observation. These observations are within reach. In the next few years and decades, we will enter the era of precision gravitational-wave physics with more sensitive detectors. Just as accelerators require larger and larger energies to probe smaller and smaller scales, more sensitive gravitational-wave detectors will be probing regions closer and closer to the horizon, potentially reaching Planck scales and beyond. What may be there, lurking?

    ↳ gr-qcastro-ph.HEhep-phphysics.space-phNat.Astron. 1 (2017) 586-591·100 citations
17. 17*

    Recent investigations of QCD at HERA

    Matthew Wing🇬🇧

    The latest results from the H1 and ZEUS collaborations which challenge the QCD description of high energy $ep$ collisions are presented. Data from HERA continue to provide precision measurements and are compared to the latest theoretical predictions. Measurements of new processes are also presented as well as investigation of regions where perturbative QCD fails to describe the data. Four themes are presented here. Measurements of hard QCD processes, prompt photon and jet production, are used to compare to the latest theoretical predictions and, in the case of jet production, used to make high-precision extractions of the strong coupling constant up to next-next-to-leading order in QCD. All H1 and ZEUS charm and beauty cross sections in deep inelastic scattering have been combined and used to extract heavy-quark masses, including the running of the charm-quark mass with the scale of the process. Factorisation in diffraction has been investigated in charm production in deep inelastic scattering and prompt photon production in diffractive photoproduction has been measured for the first time. Finally, the inclusive data on deep inelastic scattering is presented in various forms in order to allow investigation of the underlying mechanism at very low photon virtuality $Q^2$ and low Bjorken $x$.

    ↳ hep-exhep-phPoS(2018)·1 citation
18. 18*

    Structure Formation and Microlensing with Axion Miniclusters

    Malcolm Fairbairn🇬🇧 · David J. E. Marsh🇬🇧 · Jérémie Quevillon🇬🇧 · Simon Rozier🇫🇷

    If the symmetry breaking responsible for axion dark matter production occurs during the radiation-dominated epoch in the early Universe, then this produces large amplitude perturbations that collapse into dense objects known as axion miniclusters. The characteristic minicluster mass, $M_0$, is set by the mass inside the horizon when axion oscillations begin. For the QCD axion $M_0\sim 10^{-10}{M}_{\odot }$, however for an axion-like particle $M_0$ can approach $M_{\odot }$ or higher. Using the Press-Schechter formalism we compute the mass function of halos formed by hierarchical structure formation from these seeds. We compute the concentrations and collapse times of these halos and show that they can grow to be as massive as $10^6{M}_0$. Within the halos, miniclusters likely remain tightly bound, and we compute their gravitational microlensing signal taking the fraction of axion dark matter collapsed into miniclusters, $f_{\mathrm{MC}}$, as a free parameter. A large value of $f_{\mathrm{MC}}$ severely weakens constraints on axion scenarios from direct detection experiments. We take into account the non-Gaussian distribution of sizes of miniclusters and determine how this effects the number of microlensing events. We develop the tools to consider microlensing by an extended mass function of non-point-like objects, and use microlensing data to place the first observational constraints on $f_{\mathrm{MC}}$. This opens a new window for the potential discovery of the axion.

    ↳ astro-ph.COastro-ph.GAhep-phPRD(2018)·169 citations
19. 19*

    Solar Extreme UV radiation and quark nugget dark matter model

    Ariel Zhitnitsky🇨🇦

    We advocate the idea that the surprising emission of extreme ultra violet (EUV) radiation and soft x-rays from the Sun are powered externally by incident dark matter (DM) particles. The energy and the spectral shape of this otherwise unexpected solar irradiation is estimated within the quark nugget dark matter model. This model was originally invented as a natural explanation of the observed ratio ${\Omega }_{\mathrm{dark}}\sim {\Omega }_{\mathrm{visible}}$ when the DM and visible matter densities assume the same order of magnitude values. This generic consequence of the model is a result of the common origin of both types of matter which are formed during the same QCD transition and both proportional to the same fundamental dimensional parameter ${\Lambda }_{\mathrm{QCD}}$. We also present arguments suggesting that the transient brightening-like "nano-flares" in the Sun may be related to the annihilation events which inevitably occur in the solar atmosphere within this dark matter scenario.

    ↳ astro-ph.SRastro-ph.COastro-ph.HEhep-phJCAP(2017)·43 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.