Institute of Particle and Nuclear Studies

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.

The objectives of the DECi-hertz Interferometer Gravitational Wave Observatory (DECIGO) are to open a new window of observation for gravitational wave astronomy and to obtain insight into significant areas of science, such as verifying and characterizing inflation, determining the thermal history of the universe, characterizing dark energy, describing the formation mechanism of supermassive black holes in the center of galaxies, testing alternative theories of gravity, seeking black hole dark matter, understanding the physics of neutron stars and searching for planets around double neutron stars. DECIGO consists of four clusters of spacecraft in heliocentric orbits; each cluster employs three drag-free spacecraft, 1000 km apart from each other, whose relative displacements are measured by three pairs of differential Fabry–Perot Michelson interferometers. Two milestone missions, DECIGO pathfinder and Pre-DECIGO, will be launched to demonstrate required technologies and possibly to detect gravitational waves.

A combination is presented of the inclusive deep inelastic cross sections measured by the H1 and ZEUS Collaborations in neutral and charged current unpolarised e p scattering at HERA during the period 1994-2000. The data span six orders of magnitude in negative four-momentum-transfer squared, Q 2 , and in Bjorken x. The combination method used takes the correlations of systematic uncertainties into account, resulting in an improved accuracy. The combined data are the sole input in a NLO QCD analysis which determines a new set of parton distributions, HERAPDF1.0, with small experimental uncertainties. This set includes an estimate of the model and parametrisation uncertainties of the fit result.

A combination is presented of all inclusive deep
\ninelastic cross sections previously published by the H1 and
\nZEUS collaborations at HERA for neutral and charged current e± p scattering for zero beam polarisation. The datawere
\ntaken at proton beam energies of 920, 820, 575 and 460GeV
\nand an electron beam energy of 27.5GeV. The data correspond
\nto an integrated luminosity of about 1 fb−1 and span
\nsix orders ofmagnitude in negative four-momentum-transfer
\nsquared, Q2, and Bjorken x. The correlations of the systematic
\nuncertainties were evaluated and taken into account for
\nthe combination. The combined cross sections were input
\nto QCD analyses at leading order, next-to-leading order and
\nat next-to-next-to-leading order, providing a new set of parton
\ndistribution functions, called HERAPDF2.0. In addition
\nto the experimental uncertainties, model and parameterisation
\nuncertainties were assessed for these parton distribution
\nfunctions. Variants of HERAPDF2.0 with an alternative
\ngluon parameterisation, HERAPDF2.0AG, and using fixedflavour-
\nnumber schemes, HERAPDF2.0FF, are presented.
\nThe analysiswas extended by includingHERAdata on charm
\nand jet production, resulting in the variant HERAPDF2.0Jets.
\nThe inclusion of jet-production cross sections made a simultaneous
\ndetermination of these parton distributions and the
\nstrong coupling constant possible, resulting in αs (M2Z
\n) =
\n0.1183±0.0009(exp)±0.0005(model/parameterisation)±
\n0.0012(hadronisation)
\n+0.0037
\n−0.0030(scale).An extraction of xFγ Z
\n3
\nand results on electroweak unification and scaling violations
\nare also presented.

A total of 614 upward throughgoing muons of minimum energy 1.6 GeV are observed by Super-Kamiokande during 537 detector live days. The measured muon flux is $[1.74\ifmmode\pm\else\textpm\fi{}0.07(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.02(\mathrm{sys})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}{\mathrm{cm}}^{\ensuremath{-}2}{\mathrm{s}}^{\ensuremath{-}1}{\mathrm{sr}}^{\ensuremath{-}1}$ compared to an expected flux of $[1.97\ifmmode\pm\else\textpm\fi{}0.44(\mathrm{theor})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}{\mathrm{cm}}^{\ensuremath{-}2}{\mathrm{s}}^{\ensuremath{-}1}{\mathrm{sr}}^{\ensuremath{-}1}$. The absolute measured flux is in agreement with the prediction within the errors. However, the zenith-angle dependence of the observed upward throughgoing muon flux does not agree with no-oscillation predictions. The observed distortion in shape is consistent with the ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{\leftrightarrow}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ oscillation hypothesis with ${sin}^{2}2\ensuremath{\theta}>0.4$ and $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}<\ensuremath{\Delta}{m}^{2}<1\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}1}{\mathrm{eV}}^{2}$ at 90% confidence level.

Numerical-relativity simulations for the merger of binary neutron stars are performed for a variety of equations of state (EOSs) and for a plausible range of the neutron-star mass, focusing primarily on the properties of the material ejected from the system. We find that a fraction of the material is ejected as a mildly relativistic and mildly anisotropic outflow with the typical and maximum velocities $\ensuremath{\sim}0.15--0.25c$ and $\ensuremath{\sim}0.5--0.8c$ (where $c$ is the speed of light), respectively, and that the total ejected rest mass is in a wide range ${10}^{\ensuremath{-}4}--{10}^{\ensuremath{-}2}{M}_{\ensuremath{\bigodot}}$, which depends strongly on the EOS, the total mass, and the mass ratio. The total kinetic energy ejected is also in a wide range between ${10}^{49}$ and ${10}^{51}\text{ }\text{ }\mathrm{ergs}$. The numerical results suggest that for a binary of canonical total mass $2.7{M}_{\ensuremath{\bigodot}}$, the outflow could generate an electromagnetic signal observable by the planned telescopes through the production of heavy-element unstable nuclei via the $r$-process [6,20,21] or through the formation of blast waves during the interaction with the interstellar matter [7], if the EOS and mass of the binary are favorable ones.

A double-hyperfragment event has been found in a hybrid-emulsion experiment. It is identified uniquely as the sequential decay of ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{6}\mathrm{He}$ emitted from a ${\ensuremath{\Xi}}^{\ensuremath{-}}$ hyperon nuclear capture at rest. The mass of ${}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}^{6}\mathrm{He}$ and the $\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Lambda}$ interaction energy $\ensuremath{\Delta}{B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$ have been measured for the first time devoid of the ambiguities due to the possibilities of excited states. The value of $\ensuremath{\Delta}{B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$ is $1.01\ifmmode\pm\else\textpm\fi{}{0.20}_{\ensuremath{-}0.11}^{+0.18}\phantom{\rule{0ex}{0ex}}\mathrm{MeV}$. This demonstrates that the $\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Lambda}$ interaction is weakly attractive.

The possible existence of deeply bound nuclear $\overline{K}$ states is investigated theoretically for few-body systems. The nuclear ground states of a ${K}^{\ensuremath{-}}$ in ${}^{3}\mathrm{He},$ ${}^{4}\mathrm{He},$ and ${}^{8}\mathrm{Be}$ are predicted to be discrete states with binding energies of 108, 86, and 113 MeV and widths of 20, 34, and 38 MeV, respectively. The smallness of the widths arises from their energy-level locations below the $\ensuremath{\Sigma}\ensuremath{\pi}$ emission threshold. It is found that a substantial contraction of the surrounding nucleus is induced due to the strong attraction of the $I=0$ $\overline{K}N$ pair, thus forming an unusually dense nuclear medium. Formation of the $T=0{K}^{\ensuremath{-}}{\ensuremath{\bigotimes}}^{3}\mathrm{He}+{K}^{0}{\ensuremath{\bigotimes}}^{3}\mathrm{H}$ state in the ${}^{4}\mathrm{He}$ (stopped ${K}^{\ensuremath{-}},$ $n)$ reaction is proposed, with a calculated branching ratio of about 2%.

Gravitational-wave observation together with a large number of electromagnetic observations shows that the source of the latest gravitational-wave event, GW170817, detected primarily by advanced LIGO, is the merger of a binary neutron star. We attempt to interpret this observational event based on our results of numerical-relativity simulations performed so far, paying particular attention to the optical and infrared observations. We finally reach a conclusion that this event is described consistently by the presence of a long-lived hypermassive or supramassive neutron star as the merger remnant because (i) significant contamination by lanthanide elements along our line of sight to this source can be avoided by the strong neutrino irradiation from it and (ii) it could play a crucial role in producing an ejecta component of appreciable mass with fast motion in the postmerger phase. We also point out that (I) the neutron-star equation of state has to be sufficiently stiff (i.e., the maximum mass of cold spherical neutron stars, ${M}_{\mathrm{max}}$, has to be appreciably higher than $2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$) in order for a long-lived massive neutron star to be formed as the merger remnant for the binary systems of GW170817, for which the initial total mass is $\ensuremath{\gtrsim}2.73\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$, and (II) the absence of optical counterparts associated with relativistic ejecta suggests a not-extremely-high value of ${M}_{\mathrm{max}}$ approximately as $2.15--2.25\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$.

(c) The Author(s) 2014. This article is published with open access at Springerlink.com.
\nThis article is distributed under the terms of
\nthe Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. Funded by SCOAP3 / License Version CC BY 4.0.

Abstract The Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is a future Japanese space mission with a frequency band of 0.1 Hz to 10 Hz. DECIGO aims at the detection of primordial gravitational waves, which could have been produced during the inflationary period right after the birth of the Universe. There are many other scientific objectives of DECIGO, including the direct measurement of the acceleration of the expansion of the Universe, and reliable and accurate predictions of the timing and locations of neutron star/black hole binary coalescences. DECIGO consists of four clusters of observatories placed in heliocentric orbit. Each cluster consists of three spacecraft, which form three Fabry–Pérot Michelson interferometers with an arm length of 1000 km. Three DECIGO clusters will be placed far from each other, and the fourth will be placed in the same position as one of the other three to obtain correlation signals for the detection of primordial gravitational waves. We plan to launch B-DECIGO, which is a scientific pathfinder for DECIGO, before DECIGO in the 2030s to demonstrate the technologies required for DECIGO, as well as to obtain fruitful scientific results to further expand multi-messenger astronomy.

The Telescope Array (TA) experiment, located in the western desert of Utah, USA, is designed for the observation of extensive air showers from extremely high energy cosmic rays. The experiment has a surface detector array surrounded by three fluorescence detectors to enable simultaneous detection of shower particles at ground level and fluorescence photons along the shower track. The TA surface detectors and fluorescence detectors started full hybrid observation in March, 2008. In this article we describe the design and technical features of the TA surface detector.

Americanae nace como un proyecto conjunto que surge dentro de la Red Europea de Información y Documentación sobre América Latina (REDIAL), y que ha afrontado la Biblioteca de la Agencia Española de Cooperación Internacional para el Desarrollo (AECID). Esta nueva biblioteca virtual hace más accesibles los libros digitales de tema americanista a los investigadores y usuarios interesados de cualquier parte del mundo.

The ForwArd Search ExpeRiment (FASER) is an approved experiment dedicated to searching for light, extremely weakly interacting particles at the LHC. Such particles may be produced in the LHC's high-energy collisions and travel long distances through concrete and rock without interacting. They may then decay to visible particles in FASER, which is placed 480 m downstream of the ATLAS interaction point. In this work we briefly describe the FASER detector layout and the status of potential backgrounds. We then present the sensitivity reach for FASER for a large number of long-lived particle models, updating previous results to a uniform set of detector assumptions, and analyzing new models. In particular, we consider all of the renormalizable portal interactions, leading to dark photons, dark Higgs bosons, and heavy neutral leptons; light $B\ensuremath{-}L$ and ${L}_{i}\ensuremath{-}{L}_{j}$ gauge bosons; axionlike particles that are coupled dominantly to photons, fermions, and gluons through nonrenormalizable operators; and pseudoscalars with Yukawa-like couplings. We find that FASER and its follow-up, FASER 2, have a full physics program, with discovery sensitivity in all of these models and potentially far-reaching implications for particle physics and cosmology.

We present results for several light hadronic quantities (${f}_{\ensuremath{\pi}}$, ${f}_{K}$, ${B}_{K}$, ${m}_{ud}$, ${m}_{s}$, ${t}_{0}^{1/2}$, ${w}_{0}$) obtained from simulations of $2+1$ flavor domain wall lattice QCD with large physical volumes and nearly physical pion masses at two lattice spacings. We perform a short, $\mathcal{O}(3)%$, extrapolation in pion mass to the physical values by combining our new data in a simultaneous chiral/continuum ``global fit'' with a number of other ensembles with heavier pion masses. We use the physical values of ${m}_{\ensuremath{\pi}}$, ${m}_{K}$ and ${m}_{\mathrm{\ensuremath{\Omega}}}$ to determine the two quark masses and the scale---all other quantities are outputs from our simulations. We obtain results with subpercent statistical errors and negligible chiral and finite-volume systematics for these light hadronic quantities, including ${f}_{\ensuremath{\pi}}=130.2(9)\text{ }\text{ }\mathrm{MeV}$; ${f}_{K}=155.5(8)\text{ }\text{ }\mathrm{MeV}$; the average up/down quark mass and strange quark mass in the $\overline{\mathrm{MS}}$ scheme at 3 GeV, 2.997(49) and 81.64(1.17) MeV respectively; and the neutral kaon mixing parameter, ${B}_{K}$, in the renormalization group invariant scheme, 0.750(15) and the $\overline{\mathrm{MS}}$ scheme at 3 GeV, 0.530(11).

Abstract In the past decade, exotic hadrons with charm and bottom flavors have been extensively studied both in experiments and in theories. In this review, we provide topical discussions by selecting $X,Y,Z$ particles, to which Belle has made important contributions. These are $X(3872)$, $Y(4260)$, $Z_c(4430)^+$, $Z_c(3900)^+$, $Z_{b}(10610)^+$, and $Z_{b}(10650)^+$. Based on the current experimental observations, we discuss these states with emphasis on the hadronic molecule whose dynamics is governed by chiral symmetry and heavy-quark symmetry of QCD. We also mention briefly various interpretations and some theoretical predictions for the as yet undiscovered exotic hadrons.

We have simulated QCD using $2+1$ flavors of domain wall quarks and the Iwasaki gauge action on a $(2.74\text{ }\text{ }\mathrm{fm}{)}^{3}$ volume with an inverse lattice scale of ${a}^{\ensuremath{-}1}=1.729(28)\text{ }\text{ }\mathrm{GeV}$. The up and down (light) quarks are degenerate in our calculations and we have used four values for the ratio of light quark masses to the strange (heavy) quark mass in our simulations: 0.217, 0.350, 0.617, and 0.884. We have measured pseudoscalar meson masses and decay constants, the kaon bag parameter ${B}_{K}$, and vector meson couplings. We have used SU(2) chiral perturbation theory, which assumes only the up and down quark masses are small, and SU(3) chiral perturbation theory to extrapolate to the physical values for the light quark masses. While next-to-leading order formulas from both approaches fit our data for light quarks, we find the higher-order corrections for SU(3) very large, making such fits unreliable. We also find that SU(3) does not fit our data when the quark masses are near the physical strange quark mass. Thus, we rely on SU(2) chiral perturbation theory for accurate results. We use the masses of the $\ensuremath{\Omega}$ baryon, and the $\ensuremath{\pi}$ and $K$ mesons to set the lattice scale and determine the quark masses. We then find ${f}_{\ensuremath{\pi}}=124.1(3.6{)}_{\mathrm{stat}}(6.9{)}_{\mathrm{syst}}\text{ }\text{ }\mathrm{MeV}$, ${f}_{K}=149.6(3.6{)}_{\mathrm{stat}}(6.3{)}_{\mathrm{syst}}\text{ }\text{ }\mathrm{MeV}$, and ${f}_{K}/{f}_{\ensuremath{\pi}}=1.205(0.018{)}_{\mathrm{stat}}(0.062{)}_{\mathrm{syst}}$. Using nonperturbative renormalization to relate lattice regularized quark masses to regularization independent momentum scheme masses, and perturbation theory to relate these to $\overline{\mathrm{MS}}$, we find ${m}_{ud}^{\overline{\mathrm{MS}}}(2\text{ }\text{ }\mathrm{GeV})=3.72(0.16{)}_{\mathrm{stat}}(0.33{)}_{\mathrm{ren}}(0.18{)}_{\mathrm{syst}}\text{ }\text{ }\mathrm{MeV}$, ${m}_{s}^{\overline{\mathrm{MS}}}(2\text{ }\text{ }\mathrm{GeV})=107.3(4.4{)}_{\mathrm{stat}}(9.7{)}_{\mathrm{ren}}(4.9{)}_{\mathrm{syst}}\text{ }\text{ }\mathrm{MeV}$, and ${\stackrel{\texttildelow{}}{m}}_{ud}\ensuremath{\mathbin:}{\stackrel{\texttildelow{}}{m}}_{s}=1\ensuremath{\mathbin:}28.8(0.4{)}_{\mathrm{stat}}(1.6{)}_{\mathrm{syst}}$. For the kaon bag parameter, we find ${B}_{K}^{\overline{\mathrm{MS}}}(2\text{ }\text{ }\mathrm{GeV})=0.524(0.010{)}_{\mathrm{stat}}(0.013{)}_{\mathrm{ren}}(0.025{)}_{\mathrm{syst}}$. Finally, for the ratios of the couplings of the vector mesons to the vector and tensor currents (${f}_{V}$ and ${f}_{V}^{T}$, respectively) in the $\overline{\mathrm{MS}}$ scheme at 2 GeV we obtain ${f}_{\ensuremath{\rho}}^{T}/{f}_{\ensuremath{\rho}}=0.687(27)$; ${f}_{{K}^{*}}^{T}/{f}_{{K}^{*}}=0.712(12)$, and ${f}_{\ensuremath{\phi}}^{T}/{f}_{\ensuremath{\phi}}=0.750(8)$.

We study high-energy neutrino production in collimated jets inside progenitors of gamma-ray bursts (GRBs) and supernovae, considering both collimation and internal shocks. We obtain simple, useful constraints, using the often overlooked point that shock acceleration of particles is ineffective at radiation-mediated shocks. Classical GRBs may be too powerful to produce high-energy neutrinos inside stars, which is consistent with IceCube nondetections. We find that ultralong GRBs avoid such constraints and detecting the TeV signal will support giant progenitors. Predictions for low-power GRB classes including low-luminosity GRBs can be consistent with the astrophysical neutrino background IceCube may detect, with a spectral steepening around PeV. The models can be tested with future GRB monitors.

We present physical results obtained from simulations using $2+1$ flavors of domain wall quarks and the Iwasaki gauge action at two values of the lattice spacing $a$, [${a}^{\ensuremath{-}1}=1.73(3)\text{ }\text{ }\mathrm{GeV}$ and ${a}^{\ensuremath{-}1}=2.28(3)\text{ }\text{ }\mathrm{GeV}$]. On the coarser lattice, with ${24}^{3}\ifmmode\times\else\texttimes\fi{}64\ifmmode\times\else\texttimes\fi{}16$ points (where the 16 corresponds to ${L}_{s}$, the extent of the 5th dimension inherent in the domain wall fermion formulation of QCD), the analysis of C. Allton et al. (RBC-UKQCD Collaboration), Phys. Rev. D 78 is extended to approximately twice the number of configurations. The ensembles on the finer ${32}^{3}\ifmmode\times\else\texttimes\fi{}64\ifmmode\times\else\texttimes\fi{}16$ lattice are new. We explain in detail how we use lattice data obtained at several values of the lattice spacing and for a range of quark masses in combined continuum-chiral fits in order to obtain results in the continuum limit and at physical quark masses. We implement this procedure for our data at two lattice spacings and with unitary pion masses in the approximate range 290--420 MeV (225--420 MeV for partially quenched pions). We use the masses of the $\ensuremath{\pi}$ and $K$ mesons and the $\ensuremath{\Omega}$ baryon to determine the physical quark masses and the values of the lattice spacing. While our data in the mass ranges above are consistent with the predictions of next-to-leading order SU(2) chiral perturbation theory, they are also consistent with a simple analytic ansatz leading to an inherent uncertainty in how best to perform the chiral extrapolation that we are reluctant to reduce with model-dependent assumptions about higher order corrections. In some cases, particularly for ${f}_{\ensuremath{\pi}}$, the pion leptonic decay constant, the uncertainty in the chiral extrapolation dominates the systematic error. Our main results include ${f}_{\ensuremath{\pi}}=124(2{)}_{\mathrm{stat}}(5{)}_{\mathrm{syst}}\text{ }\text{ }\mathrm{MeV}$, ${f}_{K}/{f}_{\ensuremath{\pi}}=1.204(7)(25)$ where ${f}_{K}$ is the kaon decay constant, ${m}_{s}^{\overline{\mathrm{MS}}}(2\text{ }\text{ }\mathrm{GeV})=(96.2\ifmmode\pm\else\textpm\fi{}2.7)\text{ }\text{ }\mathrm{MeV}$ and ${m}_{ud}^{\overline{\mathrm{MS}}}(2\text{ }\text{ }\mathrm{GeV})=(3.59\ifmmode\pm\else\textpm\fi{}0.21)\text{ }\text{ }\mathrm{MeV}$ (${m}_{s}/{m}_{ud}=26.8\ifmmode\pm\else\textpm\fi{}1.4$) where ${m}_{s}$ and ${m}_{ud}$ are the mass of the strange quark and the average of the up and down quark masses, respectively, $[{\ensuremath{\Sigma}}^{\overline{\mathrm{MS}}}(2\text{ }\text{ }\mathrm{GeV}){]}^{1/3}=256(6)\text{ }\text{ }\mathrm{MeV}$, where $\ensuremath{\Sigma}$ is the chiral condensate, the Sommer scale ${r}_{0}=0.487(9)\text{ }\text{ }\mathrm{fm}$ and ${r}_{1}=0.333(9)\text{ }\text{ }\mathrm{fm}$.

The Telescope Array (TA) collaboration has measured the energy spectrum of ultra-high energy cosmic rays (UHECRs) with primary energies above 1.6 x 10(18) eV. This measurement is based upon four years of observation by the surface detector component of TA. The spectrum shows a dip at an energy of 4.6x10(18) eV and a steepening at 5.4x10(19) eV which is consistent with the expectation from the GZK cutoff. We present the results of a technique, new to the analysis of UHECR surface detector data, that involves generating a complete simulation of UHECRs striking the TA surface detector. The procedure starts with shower simulations using the CORSIKA Monte Carlo program where we have solved the problems caused by use of the "thinning" approximation. This simulation method allows us to make an accurate calculation of the acceptance of the detector for the energies concerned.