Mon·Feb 20, 2017Monday·February 20, 2017

1. 01*

   On new physics searches with multidimensional differential shapes

   Felipe Ferreira🇧🇷 · Sylvain Fichet🇧🇷 · Veronica Sanz🇬🇧

   In the context of upcoming new physics searches at the LHC, we investigate the impact of multidimensional differential rates in typical LHC analyses. We discuss the properties of shape information, and argue that multidimensional rates bring limited information in the scope of a discovery, but can have a large impact on model discrimination. We also point out subtleties about systematic uncertainties cancellations and the Cauchy-Schwarz bound on interference terms.

   hep-phPLB(2018)·9 citations
2. 02*

   Re-examining valence quark spin distributions

   A. I. Signal🇳🇿

   The observed deep inelastic nucleon spin asymmetries $A_1^{p,n}$ and the spin dependent quark distributions break SU(6) spin - flavour symmetry. In quark models two mechanisms for breaking SU(6) symmetry are well known: the hyperfine interaction and the pion cloud of the nucleon. I re-evaluate these mechanisms and show how the breaking of SU(6) in each case affects spin dependent valence quark distributions of the proton. In particular I investigate the properties of these mechanisms in the kinematic region $0.3<x<0.7$ and attempt to test these against known data. Both mechanisms are able to explain the quantitative features of the spin asymmetries.

   hep-phnucl-thPRD(2017)·3 citations
3. 03*

   Charmless two-body anti-triplet $b$-baryon decays

   Y.K. Hsiao🇨🇳 · Yu Yao🇨🇳 · C.Q. Geng🇨🇳

   We study the charmless two-body decays of $b$-baryons $({\Lambda }_b$, ${\Xi }_b^{-}$, ${\Xi }_b^0)$. We find that $\mathcal{B}({\Xi }_b^{-}\to \Lambda {\rho }^{-})=(2.08_{-0.51}^{+0.69})\times 10^{-6}$ and $\mathcal{B}({\Xi }_b^0\to {\Sigma }^{+}{M}^{-})=(4.45_{-1.09}^{+1.46},11.49_{-2.9}^{+3.8},4.69_{-0.79}^{+1.11},2.98_{-0.51}^{+0.76})\times 10^{-6}$ for $M^{-}=({\pi }^{-},{\rho }^{-},K^{-},K^{\ast -})$, which are compatible to $\mathcal{B}({\Lambda }_b\to p{\pi }^{-},p{K}^{-})$. We also obtain that $\mathcal{B}({\Lambda }_b\to \Lambda \omega )=(2.30\pm 0.10)\times 10^{-6}$, $\mathcal{B}({\Xi }_b^{-}\to {\Xi }^{-}\varphi ,{\Xi }^{-}\omega )\simeq \mathcal{B}({\Xi }_b^0\to {\Xi }^0\varphi ,{\Xi }^0\omega )=(5.35\pm 0.41,3.65\pm 0.16)\times 10^{-6}$ and $\mathcal{B}({\Xi }_b^{-}\to {\Xi }^{-}{\eta }^{(\prime )})\simeq \mathcal{B}({\Xi }_b^0\to {\Xi }^0{\eta }^{(\prime )})=(2.51_{-0.46}^{+0.70},2.99_{-0.57}^{+1.16})\times 10^{-6}$. For the CP violating asymmetries, we show that ${\mathcal{A}}_{CP}({\Lambda }_b\to p{K}^{\ast -})={\mathcal{A}}_{CP}({\Xi }_b^{-}\to {\Sigma }^0(\Lambda )K^{\ast -})={\mathcal{A}}_{CP}({\Xi }_b^0\to {\Sigma }^{+}{K}^{\ast -})=(19.7\pm 1.4)\%$. Similar to the charmless two-body ${\Lambda }_b$ decays, the ${\Xi }_b$ decays are accessible to the LHCb detector.

   hep-phhep-exPRD(2017)·33 citations
4. 04*

   Azimuthal flow in hadron collisions from quark-gluon string repulsion

   Igor Altsybeev🇷🇺 · Grigory Feofilov🇷🇺

   Color flux tubes (quark-gluon strings), formed at early stages of hadron-hadron collisions, may overlap in case of sufficiently high densities and interact, producing long-range azimuthal correlations. In the hypothesis of repulsive interaction, each string may acquire, before the hadronization, the additional transverse boost, which is an efficient sum of all accounted string-string interactions. This modifies transverse momenta to the particles formed in string decay, leading to modification of event-wise observables, like azimuthal asymmetry of two-particle correlations, over a wide range of rapidity. In this article we discuss results of Monte Carlo model with string repulsion, where efficient string-string interaction radius is introduced. We show that the effect of string repulsion can be the main dynamic origin of the elliptic flow and of the higher harmonics, which are reflected in the complicated structures observed in two-particle long-range correlation topology in nucleus-nucleus collisions at RHIC and at LHC.

   hep-phnucl-thEPJ Web Conf.(2016)·4 citations
5. 05*

   Nonlinear effects in gluon distribution predicted by GLR-MQ evolution equation at next-to-leading order in LHC data

   M. Lalung🇮🇳 · P. Phukan🇮🇳 · J. K. Sarma🇮🇳

   In this work we have solved the nonlinear GLR-MQ evolution equation upto next-to-leading order (NLO) by considering NLO terms of the gluon-gluon splitting functions and running coupling constant ${\alpha }_s(Q^2)$. Here, we have incorporated a Regge-like behaviour of gluon distribution in order to obtain a solution of the GLR-MQ equation in the range of $5Ge{V}^2\le Q^2\le 25Ge{V}^2$. We have studied the $Q^2$ evolution of the gluon distribution function $G(x,Q^2)$ and its nonlinear effects at small-x. It can be observed from our analysis that the nonlinearities increase with decrease in the correlation radius R of two interacting gluons, as expected. We have compared our result of $G(x,Q^2)$ as $Q^2$ increases and x decreases, for two different values of R, viz. R= 2 $Ge{V}^{-1}$ and 5 $Ge{V}^{-1}$. We have also checked the sensitivity of the Regge intercept ${\lambda }_G$ on our results. We compare our computed results with those obtained by the global analysis to parton distribution functions (PDFs) by various collaborations where LHC data have been included viz. PDF4LHC15, NNPDF3.0, ABM12 and CT14. Besides we have also shown comparison of our results with HERA PDF data viz. HERAPDF15.

   hep-phInt.J.Theor.Phys.(2017)·15 citations
6. 06*

   The Potential of the ILC for Discovering New Particles

   Keisuke Fujii🇯🇵 · Christophe Grojean🇩🇪 · Michael E. Peskin🇺🇸 · Tim Barklow🇺🇸 · Yuanning Gao🇨🇳 · Shinya Kanemura🇯🇵 · Hyungdo Kim🇰🇷 · Jenny List🇩🇪 · Mihoko Nojiri🇯🇵 · Maxim Perelstein🇺🇸 · Roman Pöschl🇫🇷 · Jürgen Reuter🇩🇪 and 13 other authors

   This paper addresses the question of whether the International Linear Collider has the capability of discovering new particles that have not already been discovered at the CERN Large Hadron Collider. We summarize the various paths to discovery offered by the ILC, and discuss them in the context of three different scenarios: 1. LHC does not discover any new particles, 2. LHC discovers some new low mass states and 3. LHC discovers new heavy particles. We will show that in each case, ILC plays a critical role in discovery of new phenomena and in pushing forward the frontiers of high-energy physics as well as our understanding of the universe in a manner which is highly complementary to that of LHC. For the busy reader, a two-page executive summary is provided at the beginning of the document.

   hep-phhep-ex42 citations
7. 07*

   Tensor-polarized structure function $b_1$ in the standard convolution description of the deuteron

   W. Cosyn🇧🇪 · Yu-Bing Dong🇨🇳 · S. Kumano🇯🇵 · M. Sargsian🇺🇸

   Tensor-polarized structure functions of a spin-1 hadron are additional observables which do not exist for the spin-1/2 nucleon. They could probe novel aspects of the internal hadron structure. Twist-2 tensor-polarized structure functions are $b_1$ and $b_2$, and they are related by the Callan-Gross-like relation in the Bjorken scaling limit. In this work, we theoretically calculate $b_1$ in the standard convolution description for the deuteron. Two different theoretical models, a basic convolution description and a virtual nucleon approximation, are used for calculating $b_1$ and their results are compared with the HERMES measurement. We found large differences between our theoretical results and the data. Although there is still room to improve by considering higher-twist effects and in the experimental extraction of $b_1$ from the spin asymmetry $A_{zz}$, there is a possibility that the large differences require physics beyond the standard deuteron model for their interpretation. Future $b_1$ studies could shed light on a new field of hadron physics. In particular, detailed experimental studies of $b_1$ will start soon at the Thomas Jefferson National Accelerator Facility. In addition, there are possibilities to investigate tensor-polarized parton distribution functions and $b_1$ at Fermi National Accelerator Laboratory and a future electron-ion collider. Therefore, further theoretical studies are needed for understanding the tensor structure of the spin-1 deuteron, including a new mechanism to explain the large differences between the current data and our theoretical results.

   hep-phhep-exhep-latnucl-ex+1PRD(2017)·51 citations
8. 08*

   Parton correlations in same-sign $W$ pair production via double parton scattering at the LHC

   Federico Alberto Ceccopieri🇧🇪 · Matteo Rinaldi🇪🇸 · Sergio Scopetta🇮🇹

   Same-sign $W$ boson pairs production is a promising channel to look for signatures of double parton interactions at the LHC. The corresponding cross section has been calculated by using double parton distribution functions, encoding two parton correlations, evaluated in a Light-Front quark model. The obtained result is in line with previous estimates which make use of an external parameter, the so called effective cross section, not necessary in our approach. The possibility to observe for the first time two-parton correlations, in the next LHC runs, has been established.

   hep-phhep-exnucl-thPRD(2017)·47 citations
9. 09*

   Light Higgsinos, Heavy Gluino and $b-\tau$ Quasi-Yukawa Unification: Will the LHC find the Gluino?

   Aditya Hebbar🇺🇸 · Qaisar Shafi🇺🇸 · Cem Salih Un🇹🇷

   A wide variety of unified models predict asymptotic relations at $M_{GUT}$ between the b quark and $\tau$ lepton Yukawa couplings. Within the framework of supersymmetric SU(4) $\times$ SU(2)${}_L\times$ SU(2)${}_R$, we explore regions of the parameter space that are compatible with b-$\tau$ quasi-Yukawa unification and the higgsinos being the lightest supersymmetric particles ($\lesssim$ 1 TeV). Among the colored sparticles, the stop weighs more than 1.5 TeV or so, whereas the squarks of the first two families are signifcantly heavier, approaching 10 TeV in some cases. The gluino mass is estimated to lie in the 2-4 TeV range which raises the important question: Will the LHC find the gluino?

   hep-phPRD(2017)·9 citations
10. 10*

    $a_1$ properties in hadronic tau decays

    Ina Lorenz🇺🇸 · Emilie Passemar🇺🇸

    Hadronic tau decays belong to the processes that show a resonance-like structure in the axial vector current in the $1-2$ GeV range. This structure, often denoted as the $a_1$ meson, seems to show different properties in different processes. The process $\tau \to 3\pi {\nu }_{\tau }$ allows for a clean separation of weak and strong effects and a clear production mechanism. We examine how this structure can be related to interactions between the three pions that emerge in the final state. In particular we start from the interactions between all two body combinations.

    hep-phPoS(2016)·4 citations
11. 11*

    Topics in Higgs Physics

    John Ellis🇬🇧

    These lecture notes review the theoretical background to the Higgs boson, provide an introduction to its phenomenology, and describe the experimental tests that lead us to think that "beyond any reasonable doubt, it is a Higgs boson". Motivations for expecting new physics beyond the Standard Model are recalled, and the Standard Model effective field theory is advocated as a tool to help search for it. The phenomenology of $N=1$ and $N=2$ supersymmetric Higgs bosons is reviewed, and the prospects for possible future Higgs factories are previewed.

    hep-phhep-exCERN Yellow Rep.School Proc.(2018)·15 citations
12. 12*

    Deciphering the MSSM Higgs Mass at Future Hadron Colliders

    Prateek Agrawal🇺🇸 · JiJi Fan🇺🇸 · Matthew Reece🇺🇸 · Wei Xue🇺🇸

    Future hadron colliders will have a remarkable capacity to discover massive new particles, but their capabilities for precision measurements of couplings that can reveal underlying mechanisms have received less study. In this work we study the capability of future hadron colliders to shed light on a precise, focused question: is the higgs mass of 125 GeV explained by the MSSM? If supersymmetry is realized near the TeV scale, a future hadron collider could produce huge numbers of gluinos and electroweakinos. We explore whether precision measurements of their properties could allow inference of the scalar masses and $\tan \beta$ with sufficient accuracy to test whether physics beyond the MSSM is needed to explain the higgs mass. We also discuss dark matter direct detection and precision higgs physics as complementary probes of $\tan \beta$. For concreteness, we focus on the mini-split regime of MSSM parameter space at a 100 TeV $pp$ collider, with scalar masses ranging from 10s to about 1000 TeV.

    hep-phJHEP(2017)·6 citations
13. 13*

    Search for sterile neutrino mixing using three years of IceCube DeepCore data

    IceCube Collaboration: M. G. Aartsen🇦🇺 · M. Ackermann🇩🇪 · J. Adams🇳🇿 · J. A. Aguilar🇧🇪 · M. Ahlers🇺🇸 · M. Ahrens🇸🇪 · I. Al Samarai🇨🇭 · D. Altmann🇩🇪 · K. Andeen🇺🇸 · T. Anderson🇺🇸 · I. Ansseau🇧🇪 · G. Anton🇩🇪 and 295 other authors

    We present a search for a light sterile neutrino using three years of atmospheric neutrino data from the DeepCore detector in the energy range of approximately $10-60$GeV. DeepCore is the low-energy sub-array of the IceCube Neutrino Observatory. The standard three-neutrino paradigm can be probed by adding an additional light ($\Delta m_{41}^2\sim 1\mathrm{e}{\mathrm{V}}^2$) sterile neutrino. Sterile neutrinos do not interact through the standard weak interaction, and therefore cannot be directly detected. However, their mixing with the three active neutrino states leaves an imprint on the standard atmospheric neutrino oscillations for energies below 100 GeV. A search for such mixing via muon neutrino disappearance is presented here. The data are found to be consistent with the standard three neutrino hypothesis. Therefore we derive limits on the mixing matrix elements at the level of $|U_{\mu 4}{|}^2<0.11$ and $|U_{\tau 4}{|}^2<0.15$ (90% C.L.) for the sterile neutrino mass splitting $\Delta m_{41}^2=1.0$ eV${}^2$.

    ↳ hep-exhep-phPRD(2017)·172 citations
14. 14*

    Neutron-proton scattering at next-to-next-to-leading order in Nuclear Lattice Effective Field Theory

    Jose Manuel Alarcón🇺🇸 · Dechuan Du🇩🇪 · Nico Klein🇩🇪 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Ning Li🇩🇪 · Bing-Nan Lu🇩🇪 · Thomas Luu🇩🇪 · Ulf-G. Meißner🇩🇪

    We present a systematic study of neutron-proton scattering in Nuclear Lattice Effective Field Theory (NLEFT), in terms of the computationally efficient radial Hamiltonian method. Our leading-order (LO) interaction consists of smeared, local contact terms and static one-pion exchange. We show results for a fully non-perturbative analysis up to next-to-next-to-leading order (NNLO), followed by a perturbative treatment of contributions beyond LO. The latter analysis anticipates practical Monte Carlo simulations of heavier nuclei. We explore how our results depend on the lattice spacing a, and estimate sources of uncertainty in the determination of the low-energy constants of the next-to-leading-order (NLO) two-nucleon force. We give results for lattice spacings ranging from a = 1.97 fm down to a = 0.98 fm, and discuss the effects of lattice artifacts on the scattering observables. At a = 0.98 fm, lattice artifacts appear small, and our NNLO results agree well with the Nijmegen partial-wave analysis for S-wave and P-wave channels. We expect the peripheral partial waves to be equally well described once the lattice momenta in the pion-nucleon coupling are taken to coincide with the continuum dispersion relation, and higher-order (N3LO) contributions are included. We stress that for center-of-mass momenta below 100 MeV, the physics of the two-nucleon system is independent of the lattice spacing.

    ↳ nucl-thhep-lathep-phEPJA(2017)·30 citations
15. 15*

    Progress in the calculation of purely leptonic $D_{(s)}$ -- decay constants from lattice QCD

    Justus Tobias Tsang🇬🇧

    We review recent progress in the calculation of the decay constants $f_D$ and $f_{D_s}$ from lattice QCD. We focus particularly on simulations with $N_f=2+1$ and $N_f=2+1+1$ and simulations with close to physical light quark masses.

    ↳ hep-lathep-phPoS(2017)·1 citation
16. 16*

    WIMP Searches at the International Linear Collider

    Moritz Habermehl🇩🇪 · Keisuke Fujii🇯🇵 · Jenny List🇩🇪 · Shigeki Matsumoto🇯🇵 · Tomohiko Tanabe🇯🇵

    Weakly Interacting Massive Particles (WIMPs, $\chi$) are candidates for Dark Matter. WIMP searches at lepton colliders are complementary to searches at hadron colliders and direct and indirect detection, since they directly probe the coupling to electrons which a priori is independent of the coupling to hadrons. Like at hadron colliders, WIMP pair production can be observed via an additional tag particle, in particular a photon from initial state radiation ($e^{+}{e}^{-}\to \chi \chi \gamma$). With this technique WIMP masses to nearly half the centre-of-mass energy can be probed. Polarised beams are essential to reduce Standard Model backgrounds and to characterize the properties of the new particles in case a signal is discovered. Prospects for a mono-photon WIMP study at the International Linear Collider will be discussed in the context of EFT. In addition, detector requirements will be presented.

    ↳ hep-exhep-phPoS(2016)·9 citations
17. 17*

    Dark Matter from Starobinsky Supergravity

    Andrea Addazi🇮🇹 · Maxim Yu. Khlopov🇷🇺

    We review our recent results on dark matter from Starobinsky supergravity. In this context, a natural candidate for Cold Dark Matter is the gravitino. On the other hand, assuming the supersymmetry broken at scales much higher than the electroweak scale, gravitinos are super heavy particles. In this case, they may be non-thermally produced during inflation, in turn originated by the scalaron field with Starobinsky's potential.Assuming gravitinos as Lightest supersymmetric particles (LSSP), the non-thermal production naturally accounts for the right amount of cold dark matter. Metastability of the gravitino LSSP leads to observable effects of their decay, putting constraints on the corresponding Unstable or Decaying Dark Matters scenarios. In this model, the gravitino mass is controlled by the inflaton field and it runs with it. This implies that a continuous spectrum of superheavy gravitinos is produced during the slow-roll epoch. Implications in phenomenology, model building in GUT scenarios, intersecting D-branes models and instantons in string theories are discussed.

    ↳ gr-qchep-phMod.Phys.Lett.A(2017)·13 citations
18. 18*

    Phenomenology of a Composite Higgs Model

    Luigi Del Debbio🇬🇧 · Christoph Englert🇬🇧 · Roman Zwicky🇬🇧

    Several UV complete models of physics beyond the Standard Model are currently under scrutiny, their low-energy dynamics being compared with the experimental data from the LHC. Lattice simulations can play a role in these studies by providing a first principles computations of the low-energy constants that describe this low-energy dynamics. In this work, we study in detail a specific model recently proposed by Ferretti, and discuss the potential impact of lattice calculations.

    ↳ hep-lathep-phPoS(2017)·1 citation
19. 19*

    Dark Catalysis

    Prateek Agrawal🇺🇸 · Francis-Yan Cyr-Racine🇺🇸 · Lisa Randall🇺🇸 · Jakub Scholtz🇺🇸

    Recently it was shown that dark matter with mass of order the weak scale can be charged under a new long-range force, decoupled from the Standard Model, with only weak constraints from early Universe cosmology. Here we consider the implications of an additional charged particle $C$ that is light enough to lead to significant dissipative dynamics on galactic times scales. We highlight several novel features of this model, which can be relevant even when the $C$ particle constitutes only a small fraction of the number density (and energy density). We assume a small asymmetric abundance of the $C$ particle whose charge is compensated by a heavy $X$ particle so that the relic abundance of dark matter consists mostly of symmetric $X$ and $\bar{X}$, with a small asymmetric component made up of $X$ and $C$. As the universe cools, it undergoes asymmetric recombination binding the free $C$s into $(XC)$ dark atoms efficiently. Even with a tiny asymmetric component, the presence of $C$ particles catalyzes tight coupling between the heavy dark matter $X$ and the dark photon plasma that can lead to a significant suppression of the matter power spectrum on small scales and lead to some of the strongest bounds on such dark matter theories. We find a viable parameter space where structure formation constraints are satisfied and significant dissipative dynamics can occur in galactic haloes but show a large region is excluded. Our model shows that subdominant components in the dark sector can dramatically affect structure formation.

    ↳ astro-ph.COhep-phJCAP(2017)·58 citations
20. 20*

    Dark Sector Cosmology

    Ricardo C. G. Landim🇧🇷

    The dark side of the universe is mysterious and its nature is still unknown. In fact, this poses perhaps as the biggest challenge in the modern cosmology. The two components of the dark sector (dark matter and dark energy) correspond today to around ninety five percent of the universe. The simplest dark energy candidate is a cosmological constant. However, this attempt presents a huge discrepancy of 120 orders of magnitude between the theoretical prediction and the observed data. Such a huge disparity motivates physicists to look into a more sophisticated models. This can be done either looking for a deeper understanding of where the cosmological constant comes from, if one wants to derive it from first principles, or considering other possibilities for accelerated expansion, such as modifications of general relativity, additional matter fields and so on. Still regarding a dynamical dark energy, there may exist a possibility of interaction between dark energy and dark matter, since their densities are comparable and, depending on the coupling used, the interaction can also alleviate the issue of why dark energy and matter densities are of the same order today. Phenomenological models have been widely explored in the literature. On the other hand, field theory models that aim a consistent description of the dark energy/dark matter interaction are still few. In this thesis, we explore either a scalar or a vector field as a dark energy candidate in several different approaches, taking into account a possible interaction between the two components of the dark sector. This thesis is based on the following papers: 1611.00428, 1605.03550, 1509.04980, 1508.07248, 1507.00902 and 1505.03243. The author also collaborated in the works 1607.03506 and 1605.05264.

    ↳ gr-qchep-phhep-th2 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.