Thu·Aug 23, 2018Thursday·August 23, 2018

1. 01*

   Multi-Higgs doublet models: the Higgs-fermion couplings and their sum rules

   Miguel P. Bento🇵🇹 · Howard E. Haber🇺🇸 · J.C. Romao🇵🇹 · Joao P. Silva🇵🇹

   This is the second of a series of papers that explores the physical parameterization, sum rules and unitarity bounds arising from a non-minimal scalar sector of the Standard Model (SM) that consists of N Higgs doublets. In this paper, we focus on the structure and implication of the Yukawa interactions that couple the N scalar doublets to the SM fermions. We employ the charged Higgs basis, which is defined as the basis of scalar fields such that the neutral scalar field vacuum expectation value resides entirely in one of the N scalar doublet fields, and the charged components of the remaining N-1 scalar doublet fields are the physical (mass-eigenstate) charged Higgs fields. Based on the structure of the Yukawa Lagrangian of the model (and as a consequence of tree-level unitarity), one may deduce numerous sum rules, several of which have not appeared previously in the literature. These sum rules can be used to uncover intimate relations between the structure of the Higgs-fermion couplings and the scalar/gauge couplings. In particular, we show that the approximate alignment limit, in which the W+W- and ZZ couplings to the observed Higgs boson are approximately SM-like, imposes significant constraints on the Higgs-fermion couplings.

   hep-phJHEP(2018)·19 citations
2. 02*

   Average Event Properties from LHC to FCC-hh

   Helen Brooks🇦🇺 · Peter Skands🇦🇺

   In the context of design studies for future $pp$ colliders, we present a set of predictions for average soft-QCD event properties for $pp$ collisions at $E_{\mathrm{CM}}=14$, $27$, and $100$ TeV. The current default Monash 2013 tune of the PYTHIA 8.2 event generator is used as the baseline for the extrapolations, with uncertainties evaluated via variations of cross-section parametrisations, PDFs, MPI energy-scaling parameters, and colour-reconnection modelling, subject to current LHC constraints. The observables included in the study are total and inelastic cross sections, inelastic average energy and track densities per unit pseudorapidity (inside $|\eta |\le 6$), average track $p_{\perp }$, and jet cross sections for 50- and 100-GeV anti-$k_T$ jets with $\Delta R=0.4$, using aMC@NLO in conjunction with PYTHIA 8 for the latter.

   hep-phhep-exEPJC(2018)·10 citations
3. 03*

   Model-Independent Prediction of $R({\eta }_c)$

   Anson Berns🇺🇸 · Henry Lamm🇺🇸

   We present a model-independent prediction for $R({\eta }_c)\equiv \mathcal{B}\mathcal{R}(B_c\to {\eta }_c{\tau }^{+}{\nu }_{\tau })/\mathcal{B}\mathcal{R}(B_c\to {\eta }_c{\mu }^{+}{\nu }_{\mu })$. This prediction is obtained from the form factors through a combination of dispersive relations, heavy-quark relations at zero-recoil, and the limited existing determinations from lattice QCD. The resulting prediction, $R({\eta }_c)=0.29(5)$, agrees with the weighted average of previous model predictions, but with reduced uncertainties.

   hep-phhep-exhep-latJHEP(2018)·25 citations
4. 04*

   A Simultaneous Description of Hadron and Jet Suppression in Heavy Ion Collisions

   Jorge Casalderrey-Solana🇪🇸 · Zachary Hulcher🇬🇧 · Guilherme Milhano🇵🇹 · Daniel Pablos🇨🇦 · Krishna Rajagopal🇺🇸

   We present a global fit to all data on the suppression of high energy jets and high energy hadrons in the most central heavy ion collisions at the LHC for two different collision energies, within a hybrid strong/weak coupling quenching model. Even though the measured suppression factors for hadrons and jets differ significantly from one another and appear to asymptote to different values in the high energy limit, we obtain a simultaneous description of all these data after constraining the value of a single model parameter. We use our model to investigate the origin of the difference between the observed suppression of jets and hadrons and relate it, quantitatively, to the observed modification of the jet fragmentation function in jets that have been modified by passage through the medium produced in heavy ion collisions. In particular, the observed increase in the fraction of hard fragments in medium-modified jets, which indicates that jets with the fewest hardest fragments lose the least energy, corresponds quantitatively to the observed difference between the suppression of hadrons and jets. We argue that a harder fragmentation pattern for jets with a given energy after quenching is a generic feature of any mechanism for the interaction between jets and the medium that they traverse that yields a larger suppression for wider jets. We also compare the results of our global fit to LHC data to measurements of the suppression of high energy hadrons in RHIC collisions, and find that with its parameter chosen to fit the LHC data our model is inconsistent with the RHIC data at the $3\sigma$ level, suggesting that hard probes interact more strongly with the less hot quark-gluon plasma produced at RHIC.

   hep-phnucl-exnucl-thPRC(2019)·72 citations
5. 05*

   Automated Calculation of $N$-jet Soft Functions

   Guido Bell🇩🇪 · Bahman Dehnadi🇩🇪 · Tobias Mohrmann🇩🇪 · Rudi Rahn🇨🇭

   We present a systematic framework for the calculation of soft functions that are defined in terms of $N\ge 2$ light-like Wilson lines. The formalism represents an extension of a method that we developed earlier for the calculation of dijet soft functions to the general $N$-jet case. We discuss the technical aspects of this generalisation, focussing on SCET-1 soft functions that obey the non-Abelian exponentiation theorem in this contribution. As a first application of our method, we consider the $N$-jettiness observable and present numerical results for the $1$-jettiness and $2$-jettiness hadron-collider soft functions to next-to-next-to-leading order in the perturbative expansion.

   hep-phPoS(2018)·17 citations
6. 06*

   Hot Axions and the $H_0$ tension

   Francesco D'Eramo🇮🇹 · Ricardo Z. Ferreira🇪🇸 · Alessio Notari🇪🇸 · José Luis Bernal🇪🇸

   Scattering and decay processes of thermal bath particles involving heavy leptons can dump hot axions in the primordial plasma around the QCD phase transition. We compute their relic density, parameterized by an effective number $\Delta N_{\mathrm{eff}}$ of additional neutrinos. For couplings allowed by current bounds, production via scattering yields $\Delta N_{\mathrm{eff}}\lesssim 0.6$ and $\Delta N_{\mathrm{eff}}\lesssim 0.2$ for the cases of muon and tau, respectively. Flavor violating tau decays to a lighter lepton plus an axion give $\Delta N_{\mathrm{eff}}\lesssim 0.3$. Such values of $\Delta N_{\mathrm{eff}}$ can alleviate the tension between the direct local measurement of the Hubble constant $H_0$ and the inferred value from observations of the Cosmic Microwave Background, assuming $\Lambda$CDM. We analyze present cosmological data from the Planck collaboration and baryon acoustic oscillations with priors given in terms of the axion-lepton couplings. For axions coupled to muons, the tension can be alleviated below the 3$\sigma$ level. Future experiments will measure $\Delta N_{\mathrm{eff}}$ with higher precision, providing an axion discovery channel and probing the role of hot axions in the $H_0$ tension.

   hep-phastro-ph.COJCAP(2018)·232 citations
7. 07*

   Sterile Neutrinos with Altered Dispersion Relations as an Explanation for Neutrino Anomalies

   Dominik Döring🇩🇪 · Heinrich Päs🇩🇪 · Philipp Sicking🇩🇪 · Thomas J. Weiler🇺🇸

   Recently the MiniBooNE Collaboration has confirmed its anomalous excess in (anti)muon- to (anti)electron-neutrino oscillation data. Combined with long-standing results from the LSND experiment this amounts to a 6.1 sigma evidence for new physics beyond the Standard Model. In this paper we develop a framework with 3 active and 3 sterile neutrinos with altered dispersion relations that provides a mechanism to explain these anomalies without being in conflict with the absence of anomalous neutrino disappearance in other neutrino oscillation experiments.

   hep-phEPJC(2020)·29 citations
8. 08*

   PDFSense: Mapping the sensitivity of hadronic experiments to nucleon structure

   Bo-Ting Wang🇺🇸 · T. J. Hobbs🇺🇸 · Sean Doyle🇺🇸 · Jun Gao🇨🇳 · Tie-Jiun Hou🇨🇳 · Pavel M. Nadolsky🇺🇸 · Fredrick I. Olness🇺🇸

   Recent high precision experimental data from a variety of hadronic processes opens new opportunities for determination of the collinear parton distribution functions (PDFs) of the proton. In fact, the wealth of information from experiments such as the Large Hadron Collider (LHC) and others, makes it difficult to quickly assess the impact on the PDFs, short of performing computationally expensive global fits. As an alternative, we explore new methods for quantifying the potential impact of experimental data on the extraction of proton PDFs. Our approach relies crucially on the correlation between theory-data residuals and the PDFs themselves, as well as on a newly defined quantity --- the sensitivity --- which represents an extension of the correlation and reflects both PDF-driven and experimental uncertainties. This approach is realized in a new, publicly available analysis package PDFSense, which operates with these statistical measures to identify particularly sensitive experiments, weigh their relative or potential impact on PDFs, and visualize their detailed distributions in a space of the parton momentum fraction x and factorization scale \mu. This tool offers a new means of understanding the influence of individual measurements in existing fits, as well as a predictive device for directing future fits toward the highest impact data and assumptions.

   hep-phPoS(2018)·1 citation
9. 09*

   Flavour-violating decays of mixed top-charm squarks at the LHC

   Amit Chakraborty🇯🇵 · Motoi Endo🇯🇵 · Benjamin Fuks🇫🇷 · Björn Herrmann🇫🇷 · Mihoko M. Nojiri🇯🇵 · Priscilla Pani🇨🇭 · Giacomo Polesello🇮🇹

   We explore signatures related to squark decays in the framework of non-minimally flavour-violating Supersymmetry. We consider a simplified model where the lightest squark consists of an admixture of charm and top flavour. By recasting the existing LHC searches for top and charm squarks, we show that the limits on squark masses from these analyses are significantly weakened when the top-charm mixing is sizeable. We propose a dedicated search for squarks based on the $tc+E_{\mathrm{T}}^{\mathrm{miss}}$ final state which enhances the experimental sensitivity for the case of high mixing, and we map its expected reach for the forthcoming runs of the LHC. We emphasize the role of analyses requiring a jet tagged as produced by the fragmentation of a charm quark in understanding the squark mixing pattern, thus providing a novel handle on new physics. Our results show that, in order to achieve full coverage of the parameter space of supersymmetric models, it is necessary to extend current experimental search programmes with analyses specifically targeting the cases where the lightest top-partner is a mixed state.

   hep-phEPJC(2018)·17 citations
10. 10*

    Pati-Salam explanations of the B-meson anomalies

    Julian Heeck🇧🇪 · Daniele Teresi🇧🇪

    We provide a combined explanation of the increasingly tantalizing $B$-meson anomalies, both in $R_{K^{(\ast )}}$ and $R_{D^{(\ast )}}$, in the Pati-Salam model with minimal matter content. This well-known model, based on the gauge group $SU(4{)}_{LC}\times SU(2{)}_L\times SU(2{)}_R$, naturally contains a variety of scalar leptoquarks with related and restricted couplings. In particular we show that the seesaw-motivated scalar leptoquark within the representation $(\overline{10},3,1)$ and its right-handed parity partner $(\overline{10},1,3)$ can solve both anomalies while making testable predictions for related observables such as $B\to K\nu \nu$ and $B\to K\mu \tau$. The solution of the $R_{K^{(\ast )}}$ anomaly alone can be related to a type-II seesaw neutrino mass structure. Explaining also $R_{D^{(\ast )}}$ requires the existence of a light right-handed neutrino, which constrains the UV structure of the model.

    hep-phJHEP(2018)·104 citations
11. 11*

    Multiple-particle interaction in $1+1$ dimensional lattice model

    Peng Guo🇺🇸 · Tyler Morris🇺🇸

    Finite volume multiple-particle interaction is studied in a two-dimensional complex ${\varphi }^4$ lattice model. The existence of analytical solutions to the ${\varphi }^4$ model in two-dimensional space and time makes it a perfect model for the numerical study of finite volume effects of multi-particle interaction. The spectra from multiple particles are extracted from the Monte Carlo simulation on various lattices in several moving frames. The $S$-matrix of multi-particle scattering in ${\varphi }^4$ theory is completely determined by two fundamental parameters: single particle mass and the coupling strength of two-to-two particle interaction. These two parameters are fixed by studying single-particle and two-particle spectra. Due to the absence of the diffraction effect in the ${\varphi }^4$ model, three-particle quantization conditions are given in a simple analytical form. The three-particle spectra from simulation show remarkable agreement with the prediction of exact solutions.

    ↳ hep-lathep-phPRD(2019)·50 citations
12. 12*

    Probing spatial variation of the fine-structure constant using the CMB

    Tristan L. Smith🇺🇸 · Daniel Grin🇺🇸 · David Robinson🇺🇸 · Davy Qi🇺🇸

    The fine-structure constant, $\alpha$, controls the strength of the electromagnetic interaction. There are extensions of the standard model in which $\alpha$ is dynamical on cosmological length and time-scales. The physics of the cosmic microwave background (CMB) depends on the value of $\alpha$. The effects of spatial variation in $\alpha$ on the CMB are similar to those produced by weak lensing: smoothing of the power spectrum, and generation of non-Gaussian features. These would induce a bias to estimates of the weak-lensing potential power spectrum of the CMB. Using this effect, Planck measurements of the temperature and polarization power spectrum, as well as estimates of CMB lensing, are used to place limits (95% C. L.) on the amplitude of a scale-invariant angular power spectrum of $\alpha$ fluctuations relative to the mean value ($C_L^{\alpha }=A_{\mathrm{SI}}^{\alpha }/[L(L+1)]$) of $A_{\mathrm{SI}}^{\alpha }\le 1.6\times 10^{-5}$. The limits depend on the assumed shape of the $\alpha$-fluctuation power spectrum. For example, for a white noise angular power spectrum ($C_L^{\alpha }=A_{\mathrm{WN}}^{\alpha }$), the limit is $A_{\mathrm{WN}}^{\alpha }\le 2.3\times 10^{-8}$. It is found that the response of the CMB to $\alpha$ fluctuations depends on a separate-universe approximation, such that theoretical predictions are only reliable for $\alpha$ multipoles with $L\lesssim 100$ . An optimal trispectrum estimator can be constructed and it is found that it is only marginally more sensitive than lensing techniques for Planck but significantly more sensitive when considering the next generation of experiments. For a future CMB experiment with cosmic-variance limited polarization sensitivity (e.g., CMB-S4), the optimal estimator could detect $\alpha$ fluctuations with $A_{\mathrm{SI}}^{\alpha }>1.9\times 10^{-6}$ and $A_{\mathrm{WN}}^{\alpha }>1.4\times 10^{-9}$.

    ↳ astro-ph.COhep-phPRD(2019)·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.