Shock Breakout in Type II Plateau Supernovae: Prospects for High Redshift Supernova Surveys

Shock breakout is the brightest radiative phenomenon in a supernova (SN) but is difficult to be observed owing to the short duration and X-ray/ultraviolet (UV)-peaked spectra. After the first observation from the rising phase reported in 2008, its observability at high redshift is attracting enormous attention. We perform multigroup radiation hydrodynamics calculations of explosions for evolutionary presupernova models with various main-sequence masses $M_{\rm MS}$, metallicities $Z$, and explosion energies $E$. We present multicolor light curves of shock breakout in Type II plateau SNe, being the most frequent core-collapse SNe, and predict apparent multicolor light curves of shock breakout at various redshifts $z$. We derive the observable SN rate and reachable redshift as functions of filter $x$ and limiting magnitude $m_{x,{\rm lim}}$ by taking into account an initial mass function, cosmic star formation history, intergalactic absorption, and host galaxy extinction. We propose a realistic survey strategy optimized for shock breakout. For example, the $g'$-band observable SN rate for $m_{g',{\rm lim}}=27.5$ mag is 3.3 SNe degree$^{-2}$ day$^{-1}$ and a half of them locates at $z\geq1.2$. It is clear that the shock breakout is a beneficial clue to probe high-$z$ core-collapse SNe. We also establish ways to identify shock breakout and constrain SN properties from the observations of shock breakout, brightness, time scale, and color. We emphasize that the multicolor observations in blue optical bands with $\sim$ hour intervals, preferably over $\geq2$ continuous nights, are essential to efficiently detect, identify, and interpret shock breakout.Comment: 26 pages, 23 figures. Accepted for publication in the Astrophysical Journal Supplement Serie

B^0-\bar{B}^0 mixing with quenched lattice NRQCD

We present our recent results for the B-parameters, which parameterize the \Delta B=2 transition amplitudes. Calculations are made in quenched QCD at \beta=5.7, 5.9, and 6.1, using NRQCD for heavy quark and the $O(a)$-improved action for light quark. The operators are perturbatively renormalized including corrections of O(\alpha_s/am_Q). We examine scaling behavior of the B-parameters in detail, and discuss the systematic uncertainties using scatter of results with different analysis procedures adopted. As a result, we find B_{B_d}(m_b)=0.84(2)(8), B_{B_s}/B_{B_d}=1.017(10)(^{+4}_{-0}) and B_{S_s}(m_b)=0.87(1)(9)(^{+1}_{-0}) in the quenched approximation.Comment: Lattice 2000 (Heavy Quark Physics), 4 pages, 4 eps-figures, Latex, typo correcte

Heavy quark expansion parameters from lattice NRQCD

Using the lattice NRQCD action for heavy quark, we calculate the heavy quark expansion parameters $\mu_{\pi}^2$ and $\mu_G^2$ for heavy-light mesons and heavy-light-light baryons. The results are compared with the mass differences among heavy hadrons to test the validity of HQET relations on the lattice.Comment: Lattice2001(heavyquark), 3 pages, 4 figure

Exploration of sea quark effects in two-flavor QCD with the O(a)-improved Wilson quark action

We explore sea quark effects in the light hadron mass spectrum in a simulation of two-flavor QCD using the nonperturbatively O(a)-improved Wilson fermion action. In order to identify finite-size effects, light meson masses are measured on 12^3x48, 16^3x48 and 20^3x48 lattices with a~0.1 fm. On the largest lattice, where the finite-size effect is negligible, we find a significant increase of the strange vector meson mass compared to the quenched approximation. We also investigate the quark mass dependence of pseudoscalar meson masses and decay constants and test the consistency with (partially quenched) chiral perturbation theory.Comment: 3 pages, 3 figures, Lattice2001(spectrum

An exact algorithm for three-flavor QCD with O(a)O(a)-improved Wilson fermions

We present an exact dynamical QCD simulation algorithm for the $O(a)$-improved Wilson fermion with odd number of flavors. Our algorithm is an extension of the non-Hermitian polynomials HMC algorithm proposed by Takaishi and de Forcrand previously. In our algorithm, the systematic errors caused by the polynomial approximation of the inverse of Dirac operator is removed by a noisy-Metropolis test. For one flavor quark it is achieved by taking the square root of the correction matrix explicitly. We test our algorithm for the case of $N_f=1+1$ on a moderately large lattice size ($16^3\times48$). The $N_f=2+1$ case is also investigated.Comment: Lattice 2001 (algorithm), 3 pages, LaTeX2e with espcrc2.st

Non-trivial phase structure of Nf=3N_f=3 QCD with O(a)O(a)-improved Wilson fermion at zero temperature

JLQCD collaboration recently started the $N_f=3$ QCD simulations with the $O(a)$-improved Wilson fermion action employing an exact fermion algorithm developed for odd number of quark flavors. It is found that this theory has an unexpected non-trivial phase structure in the $(\beta,\kappa)$ plane even at zero temperature. A detailed study is made to understand the nature of the observed phase transitions and to find the way of avoiding untolerably large lattice artifacts associated with the phase transition.Comment: 3 pages, 5 figures, Lattice2001(spectrum

Differential decay rate for B→πlνB \to \pi l \nu semileptonic decays

We present our study on $B \to \pi l \nu$ semileptonic decay form factors with NRQCD action for heavy quark from a quenched lattice QCD simulation at $\beta$=5.9 on a $16^3\times 48$ lattice. We obtain form factors defined in the context of heavy quark effective theory by Burdman et al. and find that their $1/m_B$ correction is small. The limit of physical heavy and light quark masses can be performed without introducing any model function, and we obtain a prediction for the differential decay rate $d\Gamma/dq^2$. We also discuss the soft pion limit of the form factors.Comment: Lattice 2000, 4 pages, 4 figures, Late

A possible mechanism of ultrafast amorphization in phase-change memory alloys: an ion slingshot from the crystalline to amorphous position

We propose that the driving force of an ultrafast crystalline-to-amorphous transition in phase-change memory alloys are strained bonds existing in the (metastable) crystalline phase. For the prototypical example of GST, we demonstrate that upon breaking of long Ge-Te bond by photoexcitation Ge ion shot from an octahedral crystalline to a tetrahedral amorphous position by the uncompensated force of strained short bonds. Subsequent lattice relaxation stabilizes the tetrahedral surroundings of the Ge atoms and ensures the long-term stability of the optically induced phase.Comment: 6 pages, 3 figure

Non-perturbative renormalization factors of bilinear quark operators for Kogut-Susskind fermions and light quark masses in quenched QCD

Light quark masses are computed for Kogut-Susskind fermions by evaluating non-perturbatively the renormalization factor for bilinear quark operators. Calculations are carried out in the quenched approximation at \beta=6.0, 6.2, and 6.4. For the average up and down quark mass we find $m_{\bar MS}(2 GeV)= 4.15(27) MeV$ in the continuum limit, which is significantly larger than $3.51(20) MeV$ ($q^*=1/a$) or $3.40(21) MeV$ ($q^*=\pi/a$) obtained with the one-loop perturbative renormalization factor.Comment: LATTICE98(matrixelement), 3 pages, 4 eps figure

The Peculiar Type Ib Supernova 2006jc: A WCO Wolf-Rayet Star Explosion

We present a theoretical model for Type Ib supernova (SN) 2006jc. We calculate the evolution of the progenitor star, hydrodynamics and nucleosynthesis of the SN explosion, and the SN bolometric light curve (LC). The synthetic bolometric LC is compared with the observed bolometric LC constructed by integrating the UV, optical, near-infrared (NIR), and mid-infrared (MIR) fluxes. The progenitor is assumed to be as massive as $40M_\odot$ on the zero-age main-sequence. The star undergoes extensive mass loss to reduce its mass down to as small as $6.9M_\odot$, thus becoming a WCO Wolf-Rayet star. The WCO star model has a thick carbon-rich layer, in which amorphous carbon grains can be formed. This could explain the NIR brightening and the dust feature seen in the MIR spectrum. We suggest that the progenitor of SN 2006jc is a WCO Wolf-Rayet star having undergone strong mass loss and such massive stars are the important sites of dust formation. We derive the parameters of the explosion model in order to reproduce the bolometric LC of SN 2006jc by the radioactive decays: the ejecta mass $4.9M_\odot$, hypernova-like explosion energy $10^{52}$ ergs, and ejected $^{56}$Ni mass $0.22M_\odot$. We also calculate the circumstellar interaction and find that a CSM with a flat density structure is required to reproduce the X-ray LC of SN 2006jc. This suggests a drastic change of the mass-loss rate and/or the wind velocity that is consistent with the past luminous blue variable (LBV)-like event.Comment: 12 pages, 11 figures. Accepted for publication in the Astrophysical Journa