Search

We present spectra of high-redshift supernovae (SNe) that were taken with the Subaru low resolution optical spectrograph, FOCAS. These SNe were found in SN surveys with Suprime-Cam on Subaru, the CFH12k camera on the Canada-France-Hawaii Telescope (CFHT), and the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). These SN surveys specifically targeted z>1 Type Ia supernovae (SNe Ia). From the spectra of 39 candidates, we obtain redshifts for 32 candidates and spectroscopically identify 7 active candidates as probable SNe Ia, including one at z=1.35, which is the most distant SN Ia to be spectroscopically confirmed with a ground-based telescope. An additional 4 candidates are identified as likely SNe Ia from the spectrophotometric properties of their host galaxies. Seven candidates are not SNe Ia, either being SNe of another type or active galactic nuclei. When SNe Ia are observed within a week of maximum light, we find that we can spectroscopically identify most of them up to z=1.1. Beyond this redshift, very few candidates were spectroscopically identified as SNe Ia. The current generation of super red-sensitive, fringe-free CCDs will push this redshift limit higher., 19 pages, 26 figures. PASJ in press. see http://www.supernova.lbl.gov/2009ClusterSurvey/ for additional information pertaining to the HST Cluster SN Survey

We report the discovery of a multiply lensed Ly alpha emitter at z = 3.90 behind the massive cluster WARPS J1415.1+3612 at z = 1.026. Images taken by the Hubble Space Telescope using the Advanced C ...

Using the sample of Type Ia supernovae (SNe Ia) discovered by the Hubble Space Telescope (HST) Cluster Supernova Survey and augmented with HST-observed SNe Ia in the GOODS fields, we search for correlations between the properties of SNe and their host galaxies at high redshift. We use galaxy color and quantitative morphology to determine the red sequence in 25 clusters and develop a model to distinguish passively evolving early-type galaxies from star-forming galaxies in both clusters and the field. With this approach, we identify six SN Ia hosts that are early-type cluster members and eleven SN Ia hosts that are early-type field galaxies. We confirm for the first time at z>0.9 that SNe Ia hosted by early-type galaxies brighten and fade more quickly than SNe Ia hosted by late-type galaxies. We also show that the two samples of hosts produce SNe Ia with similar color distributions. The relatively simple spectral energy distributions (SEDs) expected for passive galaxies enable us to measure stellar masses of early-type SN hosts. In combination with stellar mass estimates of late-type GOODS SN hosts from Thomson & Chary (2011), we investigate the correlation of host mass with Hubble residual observed at lower redshifts. Although the sample is small and the uncertainties are large, a hint of this relation is found at z>0.9. By simultaneously fitting the average cluster galaxy formation history and dust content to the red-sequence scatters, we show that the reddening of early-type cluster SN hosts is likely E(B-V), Comment: 37 pages, 15 figures

The recent robust and homogeneous analysis of the world's supernova distance-redshift data, together with cosmic microwave background and baryon acoustic oscillation data, provides a powerful tool for constraining cosmological models. Here we examine particular classes of scalar field, modified gravity, and phenomenological models to assess whether they are consistent with observations even when their behavior deviates from the cosmological constant Lambda. Some models have tension with the data, while others survive only by approaching the cosmological constant, and a couple are statistically favored over LCDM. Dark energy described by two equation of state parameters has considerable phase space to avoid Lambda and next generation data will be required to constrain such physics., Comment: 32 pages, 19 figures

We present observations of SCP 06F6, an unusual optical transient discovered during the Hubble Space Telescope Cluster Supernova Survey. The transient brightened over a period of ~100 days, reached a peak magnitude of ~21.0 in both i_775 and z_850, and then declined over a similar timescale. There is no host galaxy or progenitor star detected at the location of the transient to a 3 sigma upper limit of i_775 = 26.4 and z_850 = 26.1, giving a corresponding lower limit on the flux increase of a factor of ~120. Multiple spectra show five broad absorption bands between 4100 AA and 6500 AA and a mostly featureless continuum longward of 6500 AA. The shape of the lightcurve is inconsistent with microlensing. The transient's spectrum, in addition to being inconsistent with all known supernova types, is not matched to any spectrum in the Sloan Digital Sky Survey (SDSS) database. We suggest that the transient may be one of a new class., 5 pages, 4 figures. Accepted for publication in ApJ. Data are available at http://supernova.lbl.gov/2006Transient/

We have searched for a heavy charged lepton with an associated neutrino of nearly the same mass in {ital e}{sup +}{ital e}{sup {minus}} annihilation data taken with the Mark II detector at a center-of-mass energy of 29 GeV. In order to suppress contamination from conventional two-photon reactions, this analysis uses a novel, radiative-tagging technique. Requiring the presence of an isolated, energetic photon allows a search for lepton doublets with mass splittings smaller than that previously accessible to experiment. No evidence for such a new lepton doublet has been found, enabling limits to be placed on allowed mass combinations. Mass splittings as low as 250--400 MeV/{ital c}{sup 2} are excluded for charged-lepton masses between 500 MeV/{ital c}{sup 2} and 10 GeV/{ital c}{sup 2}.

Data taken by the Mark II detector at the PEP storage ring was used to measure the rate of dilepton production in multihadronic events produced by e + e − annihilation at √ s =29 GeV. We determine the probability that a hadron initially containing a b (b) quark decays to a positive (negative) lepton to be 0.17 −0.08 +0.15 , with 90% confidence level limits of 0.06 and 0.38.

Published B and V fluxes from nearby Type Ia supernovae are fitted to light-curve templates with 4-6 adjustable parameters. Separately, B magnitudes from the same sample are fitted to a linear dependence on B-V color within a post-maximum time window prescribed by the CMAGIC method. These fits yield two independent SN magnitude estimates B_max and B_BV. Their difference varies systematically with decline rate Delta m_15 in a form that is compatible with a bilinear but not a linear dependence; a nonlinear form likely describes the decline-rate dependence of B_max itself. A Hubble fit to the average of B_max and B_BV requires a systematic correction for observed B-V color that can be described by a linear coefficient R = 2.59 +- 0.24, well below the coefficient R_B ~ 4.1 commonly used to characterize the effects of Milky Way dust. At 99.9% confidence the data reject a simple model in which no color correction is required for SNe that are clustered at the blue end of their observed color distribution. After systematic corrections are performed, B_max and B_BV exhibit mutual rms intrinsic variation equal to 0.074 +- 0.019 mag, of which at least an equal share likely belongs to B_BV. SN magnitudes measured using maximum-luminosity or CMAGIC methods show comparable rms deviations of order ~ 0.14 mag from the Hubble line. The same fit also establishes a 95% confidence upper limit of 486 km/s on the rms peculiar velocity of nearby SNe relative to the Hubble flow., 21 pages, 11 figures, 10 tables, to appear in The Astrophysical Journal, uses emulateapj_051214.cls

For true insight into the nature of dark energy, measurements of the precision and accuracy of the Supernova/Acceleration Probe (SNAP) are required. Precursor or scaled-down experiments are unavoidably limited, even for distinguishing the cosmological constant. They can pave the way for, but should not delay, SNAP by developing calibration, refinement, and systematics control (and they will also provide important, exciting astrophysics).

Mission requirements, the baseline design, and optical systems budgets for the SuperNova/Acceleration Probe (SNAP) telescope are presented. SNAP is a proposed space-based experiment designed to study dark energy and alternate explanations of the acceleration of the universe’s expansion by performing a series of complementary systematics-controlled astrophysical measurements. The goals of the mission are a Type Ia supernova Hubble diagram and a wide-field weak gravitational lensing survey. A 2m widefield three-mirror telescope feeds a focal plane consisting of 36 CCDs and 36 HgCdTe detectors and a high-efficiency, low resolution integral field spectrograph. Details of the maturing optical system, with emphasis on structural stability during terrestrial testing as well as expected environments during operations at L2 are discussed. The overall stray light mitigation system, including illuminated surfaces and visible objects are also presented.

A well-adapted visible and infrared spectrograph has been developed for the SNAP (SuperNova/Acceleration Probe) experiment proposed for JDEM. The primary goal of this instrument is to ensure the control of Type Ia supernovae. The spectrograph is also a key element for calibration and is able to measure redshift of some thousands of galaxy spectra both in visible and IR. An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented. We present the current design and expected performances. We show that with the current optimization and the proposed technology, we expect the most sensitive instrument proposed on this kind of mission. We recall the readiness of the concept and of the slicer technology thanks to large prototyping efforts performed in France which validate the proposition

A wide field space-based imaging telescope is necessary to fully exploit the technique of observing dark matter via weak gravitational lensing. This first paper in a three part series outlines the survey strategies and relevant instrumental parameters for such a mission. As a concrete example of hardware design, we consider the proposed Supernova/Acceleration Probe (SNAP). Using SNAP engineering models, we quantify the major contributions to this telescope's Point Spread Function (PSF). These PSF contributions are relevant to any similar wide field space telescope. We further show that the PSF of SNAP or a similar telescope will be smaller than current ground-based PSFs, and more isotropic and stable over time than the PSF of the Hubble Space Telescope. We outline survey strategies for two different regimes - a ``wide'' 300 square degree survey and a ``deep'' 15 square degree survey that will accomplish various weak lensing goals including statistical studies and dark matter mapping., 25 pages, 8 figures, 1 table, replaced with Published Version

36 pags., 13 figs., 31 tabs., 1 app., We report measurements of ΩM, ΩΛ w from 11 supernovae (SNe) at z ¼ 0:36 0:86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This is an independent set of high-redshift SNe that confirms previous SN evidence for an accelerating universe. The high-quality light curves available from photometry on WFPC2 make it possible for these 11 SNe alone to provide measurements of the cosmological parameters comparable in statistical weight to the previous results. Combined with earlier Supernova Cosmology Project data, the new SNe yield a measurement of the mass density ΩM ¼ 0:25þ0:07 Ω0:06 ðstatisticalÞ Λ 0:04 (identified systematics), or equivalently, a cosmological constant of ΩΛ ¼ 0:75þ0:06 Ω0:07 ðstatisticalÞ Λ 0:04 (identified systematics), under the assumptions of a flat universe and that the dark energy equation-of-state parameter has a constant value w ¼ Ω1.When the SN results are combined with independent flat-universe measurements of ΩM from cosmic microwave background and galaxy redshift distortion data, they provide a measurement of w ¼ Ω1:05þ0:15 Ω0:20 ðstatisticalÞ Λ 0:09 (identified systematic), if w is assumed to be constant in time. In addition to high-precision light-curve measurements, the new data offer greatly improved color measurements of the high-redshift SNe and hence improved host galaxy extinction estimates. These extinction measurements show no anomalous negative E(BΩ) at high redshift. The precision of the measurements is such that it is possible to perform a host galaxy extinction correction directly for individual SNe without any assumptions or priors on the parent E(BΩV) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with PðΩΛ > 0Þ > 0:99, a result consistent with previous and current SN analyses that rely on the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution., Support for this work was provided by NASA through grants HST-GO-07336.01-A and HST-GO-08346.01-A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work was supported in part by the Director, Office of Science,Office of High Energy and Nuclear Physics, of the US Department of Energy under Contract DE-AC03- 76SF000098, by the Center for Particle Astrophysics, an NSF Science and Technology Center operated by the University of California, Berkeley, under Cooperative Agreement AST 91-20005. This work was supported in part by a NASA LTSA grant to P. E. N., G. A., S. P., and S. E. D., and W. M. W.-V. was supported in part by a National Science Foundation Graduate Research Fellowship. A.G. is a Royal Swedish Academy Research Fellow supported by a grant from the Knut and Alice Wallenberg Foundation.

(Abridged) We present new results on the Hubble diagram of distant type Ia supernovae (SNe Ia) segregated according to the type of host galaxy. This makes it possible to check earlier evidence for a cosmological constant by explicitly comparing SNe residing in galaxies likely to contain negligible dust with the larger sample. The cosmological parameters derived from these SNe Ia hosted by presumed dust-free early-type galaxies supports earlier claims for a cosmological constant, which we demonstrate at 5 sigma significance, and the internal extinction implied is small even for late-type systems (A_B, MNRAS; post-referee version. 21 pages, 10 figures including 4 colour figures. Preprint also available at http://supernova.lbl.gov/

A well-adapted spectrograph concept has been developed for the SNAP (SuperNova/Acceleration Probe) experiment. The goal is to ensure proper identification of Type Ia supernovae and to standardize the magnitude of each candidate by determining explosion parameters. An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented in this paper. The spectrograph concept is optimized to have very high efficiency and low spectral resolution (R {approx} 100), constant through the wavelength range (0.35-1.7{micro}m), adapted to the scientific goals of the mission.

We show empirically that fits to the color-magnitude relation of Type Ia supernovae after optical maximum can provide accurate relative extragalactic distances. We report the discovery of an empirical color relation for Type Ia light curves: During much of the first month past maximum, the magnitudes of Type Ia supernovae defined at a given value of color index have a very small magnitude dispersion; moreover, during this period the relation between $B$ magnitude and $B-V$ color (or $B-R$ or $B-I$ color) is strikingly linear, to the accuracy of existing well-measured data. These linear relations can provide robust distance estimates, in particular, by using the magnitudes when the supernova reaches a given color. After correction for light curve strech factor or decline rate, the dispersion of the magnitudes taken at the intercept of the linear color-magnitude relation are found to be around 0$^m$.08 for the sub-sample of supernovae with \BVm $\le 0^m.05$, and around 0$^m$.11 for the sub-sample with \BVm $\le 0^m.2$. This small dispersion is consistent with being mostly due to observational errors. The method presented here and the conventional light curve fitting methods can be combined to further improve statistical dispersions of distance estimates. It can be combined with the magnitude at maximum to deduce dust extinction. The slopes of the color-magnitude relation may also be used to identify intrinsically different SN Ia systems. The method provides a tool that is fundamental to using SN Ia to estimate cosmological parameters such as the Hubble constant and the mass and dark energy content of the universe., ApJ, in press

The SuperNova/Acceleration Probe (SNAP) mission will require a two-meter class telescope delivering diffraction limited images spanning a one degree field in the visible and near infrared wavelength regime. This requirement, equivalent to nearly one billion pixel resolution, places stringent demands on its optical system in terms of field flatness, image quality, and freedom from chromatic aberration. We discuss the advantages of annular-field three-mirror anastigmat (TMA) telescopes for applications such as SNAP, and describe the features of the specific optical configuration that we have baselined for the SNAP mission. We discuss the mechanical design and choice of materials for the telescope. Then we present detailed ray traces and diffraction calculations for our baseline optical design. We briefly discuss stray light and tolerance issues, and present a preliminary wavefront error budget for the SNAP Telescope. We conclude by describing some of tasks to be carried out during the upcoming SNAP research and development phase.

The SuperNova / Acceleration Probe (SNAP) is a space-based experiment to measure the expansion history of the Universe and study both its dark energy and the dark matter. The experiment is motivated by the startling discovery that the expansion of the Universe is accelerating. A 0.7 square-degree imager comprised of 36 large format fully-depleted n-type CCD's sharing a focal plane with 36 HgCdTe detectors forms the heart of SNAP, allowing discovery and lightcurve measurements simultaneously for many supernovae. The imager and a high-efficiency low-resolution integral field spectrograph are coupled to a 2-m three mirror anastigmat wide-field telescope, which will be placed in a high-earth orbit. The SNAP mission can obtain high-signal-to-noise calibrated light-curves and spectra for over 2000 Type Ia supernovae at redshifts between z=0.1 and 1.7. The resulting data set can not only determine the amount of dark energy with high precision, but test the nature of the dark energy by examining its equation of state. In particular, dark energy due to a cosmological constant can be differentiated from alternatives such as "quintessence", by measuring the dark energy's equation of state to an accuracy of +/-0.05, and by studying its time dependence., This paper will be published in SPIE Proceedings Vol 4835 and is made available as an electronic preprint with permission of SPIE

The Supernova/Acceleration Probe (SNAP) is a proposed space-borne observatory that will survey the sky with a wide-field optical/near-infrared (NIR) imager. The images produced by SNAP will have an unprecedented combination of depth, solid-angle, angular resolution, and temporal sampling. For 16 months each, two 7.5 square-degree fields will be observed every four days to a magnitude depth of AB=27.7 in each of the SNAP filters, spanning 3500-17000\AA. Co-adding images over all epochs will give AB=30.3 per filter. In addition, a 300 square-degree field will be surveyed to AB=28 per filter, with no repeated temporal sampling. Although the survey strategy is tailored for supernova and weak gravitational lensing observations, the resulting data will support a broad range of auxiliary science programs., Comment: This paper will be published in SPIE Proceedings Vol. 4836 and is made available as an electronic preprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited

We present measurements of the rates of high-redshift Type Ia supernovae derived from the Subaru/XMM-Newton Deep Survey (SXDS). We carried out repeat deep imaging observations with Suprime-Cam on the Subaru Telescope, and detected 1040 variable objects over 0.918 deg$^2$ in the Subaru/XMM-Newton Deep Field. From the imaging observations, light curves in the observed $i'$-band are constructed for all objects, and we fit the observed light curves with template light curves. Out of the 1040 variable objects detected by the SXDS, 39 objects over the redshift range $0.2 < z < 1.4$ are classified as Type Ia supernovae using the light curves. These are among the most distant SN Ia rate measurements to date. We find that the Type Ia supernova rate increase up to $z \sim 0.8$ and may then flatten at higher redshift. The rates can be fitted by a simple power law, $r_V(z)=r_0(1+z)^\alpha$ with $r_0=0.20^{+0.52}_{-0.16}$(stat.)$^{+0.26}_{-0.07}$(syst.)$\times 10^{-4} {\rm yr}^{-1}{\rm Mpc}^{-3}$, and $\alpha=2.04^{+1.84}_{-1.96}$(stat.)$^{+2.11}_{-0.86}$(syst.)., Comment: 21 pages, 16 figures, accepted to PASJ

We have begun a program to discover high-redshift supernovae ($z \approx$ 0.25--0.5), and study them with follow-up photometry and spectroscopy. We report here our first discovery, a supernova at $z = 0.458$. The photometry for this supernova closely matches the lightcurve calculated for this redshift from the template of well-observed nearby Type Ia supernovae. We discuss the measurement of the deceleration parameter $q_0$ using such high-redshift supernovae, and give the best fit value assuming this one supernova is a normal, unextincted Type Ia. We describe the main sources of error in such a measurement of $q_0$, and ways to reduce these errors., Comment: Latex using aasms.sty and three postcript files uuencoded compressed. Ap.J.Lett., 440:L41, 1995 (posted for easy access). Complete postscript version also available at http://www-supernova.lbl.gov/public/index.html

We present ACS, NICMOS, and Keck AO-assisted photometry of 20 Type Ia supernovae SNe Ia from the HST Cluster Supernova Survey. The SNe Ia were discovered over the redshift interval 0.623 < z < 1.415. Fourteen of these SNe Ia pass our strict selection cuts and are used in combination with the world's sample of SNe Ia to derive the best current constraints on dark energy. Ten of our new SNe Ia are beyond redshift $z=1$, thereby nearly doubling the statistical weight of HST-discovered SNe Ia beyond this redshift. Our detailed analysis corrects for the recently identified correlation between SN Ia luminosity and host galaxy mass and corrects the NICMOS zeropoint at the count rates appropriate for very distant SNe Ia. Adding these supernovae improves the best combined constraint on the dark energy density \rho_{DE}(z) at redshifts 1.0 < z < 1.6 by 18% (including systematic errors). For a LambdaCDM universe, we find \Omega_\Lambda = 0.724 +0.015/-0.016 (68% CL including systematic errors). For a flat wCDM model, we measure a constant dark energy equation-of-state parameter w = -0.985 +0.071/-0.077 (68% CL). Curvature is constrained to ~0.7% in the owCDM model and to ~2% in a model in which dark energy is allowed to vary with parameters w_0 and w_a. Tightening further the constraints on the time evolution of dark energy will require several improvements, including high-quality multi-passband photometry of a sample of several dozen z>1 SNe Ia. We describe how such a sample could be efficiently obtained by targeting cluster fields with WFC3 on HST., Comment: 27 pages, 11 figures. Submitted to ApJ. This first posting includes updates in response to comments from the referee. See http://www.supernova.lbl.gov for other papers in the series pertaining to the HST Cluster SN Survey. The updated supernova Union2.1 compilation of 580 SNe is available at http://supernova.lbl.gov/Union

We present a new high-statistics measurement of the cross section for the process {ital e}{sup +}{ital e}{sup {minus}}{r arrow}{ital e}{sup +}{ital e}{sup {minus}}{pi}{sup +}{pi}{sup {minus}} at a center-of-mass energy of 29 GeV for invariant pion-pair masses {ital M}({pi}{sup +}{pi}{sup {minus}}) between 350 MeV/{ital c}{sup 2} and 1.6 GeV/{ital c}{sup 2}. We observe the {ital f}{sub 2}(1270) and measure its radiative width to be 3.15{plus minus}0.04{plus minus}0.39 keV. We also observe an enhancement in the {pi}{sup +}{pi}{sup {minus}} spectrum near 1 GeV. General agreement is found with unitarized models of the {gamma}{gamma}{r arrow}{pi}{sup +}{pi}{sup {minus}} reaction that include final-state interactions.

We have studied several features of the production of charged-hadron pairs by ..gamma gamma.. collisions. We have measured the f/sup 0/ partial width GAMMA/sub f//sup 0/..--> gamma gamma..(Q/sup 2/) for Q/sup 2/ in the range 0 gamma gamma.. = 2.52 +- 0.13 +- 0.38 keV at Q/sup 2/roughly-equal0. The measured Q/sup 2/ dependence is in agreement with the generalized vector-dominance model. The cross section for ..gamma gamma -->..(..pi../sup +/..pi../sup -/+K/sup +/K/sup -/) in the mass region 1.6< or =M/sub pipi/< or =2.5 GeV/c/sup 2/ has also been measured and the result compared with that expected from the QCD continuum.

This paper presents a study of events produced in 29-GeV electron-positron annihilation in which there are just two noncollinear charged particles, no detected photons, and two or more undetected particles. These events can be explained by attributing them primarily to the reactions e/sup +/e/sup -/..-->..e/sup +/e/sup -/e/sup +/e/sup -/ and e/sup +/e/sup -/..-->..e/sup +/e/sup -/..mu../sup +/..mu../sup -/ where just two particles appear in the Mark II detector. There is no evidence for unconventional sources for such events.

The Mark II detector has been upgraded in preparation for its role as the first detector to take data at the Stanford Linear Collider. The new detector components include the central drift chamber, the time-of-flight system, the coil, the endcap electromagnetic calorimeters and the beam energy and luminosity measuring devices. There have also been improvements in detector hermeticity. All of the major components were installed for a test run at the PEP storage ring (√s = 29 GeV) in 1985. This paper describes the upgraded detector, including its trigger and data acquisition systems, and gives performance figures for its components. Future improvements are also discussed.

In a 48 000-picture exposure of the Fermilab 30-inch hydrogen bubble chamber to a 205 GeV/ c π − beam, we have measured 169 events of the reaction, π − p → π − π + π − p, with a cross section of 635 ± 61 μ b. This reaction proceeds almost entirely via low mass π − → 3 π and p → p ππ dissociation. Factorization is satisfied for p → pππ dissociation in πp and pp interactions.

Production rates of multijet hadronic final states are studied ine + e − annihilation at 29 GeV center of mass energy. QCD shower model calculations with exact first order matrix element weighting at the first gluon vertex are capable of reproducing the observed multijet event rates over a large range of jet pair masses. The method used to reconstruct jets is well suited for directly comparing experimental jet rates with parton rates calculated in perturbative QCD. Evidence for the energy dependene of α s is obtained by comparing the observed production rates of 3-jet events with results of similar studies performed at higher center of mass energies.

The inclusive ϱ ° production cross section has been measured in the reaction π − p → π + π − X at 205 GeV/ c . We find σ ( ϱ ° ) = 13.5 ± 3.4 mb, with most of the production occuring in the central region. Assuming σ ( ϱ + ) ≈ σ ( ϱ − ) ≈ σ ( ϱ ° ), it is concluded that approximately one-third of the pions at this energy come from ϱ -decay.

We use data from the Mark II experiment at PEP to search for the process B→h 0 X for m h 0 between 50 and 210 MeV/ c 2 . No evidence for the Higgs boson is seen in this mass range. The limit obtained rules out the standard Higgs boson for masses between 70 and 210 MeV/ c 2 and significantly constrains extensions of the Higgs sector.

We have measured the branching ratios for a number of psi (3095) decay modes involving protons or ..lambda..'s. We present an analysis of the properties of these final states, which provides information on psi (3095) quantum numbers and the presence of resonances in the final states.

The production decay modes, spin, and mass of D mesons are reviewed. Properties of the F meson are discussed briefly. (AIP)

We have analyzed the reactions of the type K + p → Y NN (π) in K+p interactions at 9 GeV/c, where Ȳ refers to a ∧ or Σ antihyperon. We have also studied the production of  − in the reaction K + p →  − YN (π) and of antiprotons in the reaction K + p → K + p p p . With twice data previously reported we observe again a low-mass enhancement in the ∧ N final state and also observe some indications of a similar enhancement in the non-exotic Σ ± N final states. This enhancement has the quantum numbers of an I = 1 2 K ∗ resonance with mass M = 2240 +- 20 MeV and width Л = 80 ± 20 MeV .

Recent observations of angular distributions of $\ensuremath{\pi}$ mesons in $\overline{p}\ensuremath{-}p$ annihilation indicate a deviation from the predictions of the usual Fermi statistical model. In order to shed light on these phenomena, a modification of the statistical model is studied. We retain the assumption that the transition rate into a given final state is proportional to the probability of finding $N$ free $\ensuremath{\pi}$ mesons in the reaction volume, but express this probability in terms of wave functions symmetrized with respect to particles of like charge. The justification of this assumption is discussed. The model reproduces the experimental results qualitatively, provided the radius of the interaction volume is between one-half and three-fourths of the pion Compton wavelength; the dependence of angular correlation effects on the value of the radius is rather sensitive. Quantitatively, there seems to remain some discrepancy, but we cannot say whether this is due to experimental uncertainties or to some other dynamic effects. In the absence of information on $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ interactions and of a fully satisfactory explanation of the mean pion multiplicity for annihilation, we wish to emphasize the preliminary nature of our results. We consider them, however, as an indication that the symmetrization effects discussed here may well play a major role in the analysis of angular distributions. It is pointed out that in this respect the energy dependence of the angular correlations may provide valuable clues for the validity of our model.

We present angular distributions for production and decay of the quasi- two-body final states KΔ(1236) and K ∗ (891)p produced in K + p interactions at 864, 969, 1207, 1367 and 1585 MeV/ c . The analysis of these distributionsleads to the following conclusions: (a) KΔ(1236) production near threshold is largely via P-waves and is, except for coupling constants, fairly well approximated at all momenta by the predictions of the Stodolsky-Sakurai ϱ-exchange model; (b) K ∗ (891)p production appears dominated by vector exchange down to threshold, and no evidence of significant relative increase in pseudoscalar exchange contribution at low energy is seen; (c) study of the partial-wave structure of KΔ(1236) production shows no evidence of resonant behavior at the total cross-section peak near 1200 MeV/ c .

Thirty-five antiproton stars have been found in an emulsion stack exposed to a 700-Mev/c negative particle beam. Of these antiprotons, 21 annihilate in flight and three give large-angle scatters ($\ensuremath{\theta}g15\ifmmode^\circ\else\textdegree\fi{}$, ${T}_{\overline{p}}g50$ Mev), while 14 annihilate at rest. From the interactions in flight we obtain the total cross section for antiproton interaction: $\frac{{\ensuremath{\sigma}}_{\overline{p}}}{{\ensuremath{\sigma}}_{0}}=2.9\ifmmode\pm\else\textpm\fi{}0.7$, where ${\ensuremath{\sigma}}_{0}=\ensuremath{\pi}{{R}_{0}}^{2}$ and ${R}_{0}=1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}{A}^{\frac{1}{3}}$ cm. This cross section was measured at an average antiproton energy of ${\overline{T}}_{\overline{p}}=140$ Mev.We also find that the antiproton-nucleon annihilation proceeds primarily through pion production with occasional emission of $K$ particles. On the average 5.3\ifmmode\pm\else\textpm\fi{}0.4 pions are produced in the primary process; of these, 1 pion is absorbed and 0.3 inelastically scattered. From the small fraction of pions absorbed, we conclude that the annihilation occurs mainly at the surface of the nucleus at a distance larger than the conventional radius.A total energy balance of particles emitted in the annihilation gives a ratio of charged to neutral pions consistent with charge independence. Conversely, assuming charge independence, we conclude that the energy going into electromagnetic radiation or neutrinos is small.Comparisons with the Fermi statistical model and the Lepore-Neuman statistical model have been made. Good agreement with the experimental results on the annihilation process can be obtained through appropriate choice of the interaction volume parameters.Several different estimates of the antiproton mass are in good agreement and suggest strongly that the antiproton mass is the same as the proton mass within an accuracy of 2\textonehalf{}%.A study of the elastic scattering of the antiprotons down to angles of 2\ifmmode^\circ\else\textdegree\fi{} suggests a possible destructive interference between nuclear and Coulomb scattering.

The study of the Kπ system in the channel K+π−Δ++ is complicated by the presence of the broad low-mass Δ++π− enhancement centered near 1580 MeV. A cut which removes this effect reveals a break in the t′ distribution at |t′| ≈ 0.05 (GeV/c)2, with a very steep forward peak of slope a = 23.6±5.2 (GeV/c)−2 for 2. |t′| ;.sfnc;t′| ⩾ 0.05 (GeV/c) We associate this forward peak with a single-pion-exchange mechanism. A small enhancement at M(K+π−) ≈ 1100 MeV is observed in a t′ region dominated by non-pion-exchange mechanisms.

Study of 1.96-BeV/c ${K}^{+}p$ interactions in the Brookhaven 20-in. liquid-hydrogen bubble chamber has yielded a measurement of the elastic-scattering cross section $\ensuremath{\sigma}=7.5\ifmmode\pm\else\textpm\fi{}0.7$ mb. A fit to the differential cross section versus momentum transfer of the form ${\ensuremath{\sigma}}_{0}{e}^{\ensuremath{-}\ensuremath{\alpha}t}$ gives, for the interval $0.01 {(\frac{\mathrm{BeV}}{c})}^{2}ltl0.60 {(\frac{\mathrm{BeV}}{c})}^{2}$, $\ensuremath{\alpha}=3.1\ifmmode\pm\else\textpm\fi{}0.3$ ${(\mathrm{B}\mathrm{e}\mathrm{V}/\mathit{c})}^{\ensuremath{-}2}$, and ${\ensuremath{\sigma}}_{0}=4.8\ifmmode\pm\else\textpm\fi{}0.5$ mb/sr. The total cross section obtained is 19.4\ifmmode\pm\else\textpm\fi{}2.0 mb with single-pion production dominant.

We present results on the study of the reaction K + p → K O π at GeV/ c . The reaction proceeds almost entirely through the production of K 890 ∗ , K 1420 ∗ and Δ 1236 ++ . The spin parity of the K 1420 ∗ is shown to be J P = 2 + , with 18% pseudoscalar and 72% vector exchange in its production, the same proportion as for K 890 ∗ production. The dependence of the cross sections on incident momentum for the reactions K + p → K 890 ∗ p , K 1420 ∗ p , and K O Δ 1236 ++ appear to fall somewhat more rapidly than the predictions of a simple Regge-pole-exchange model.

We present evidence for structure in the Kπ system at a mass near 1.85 GeV in the reaction K+n→K+π−p at 12 GeV/c. One interpretation of the observations is the production by pion exchange of a J P = 3 − K ∗ resonance at about this mass, which interferes strongly with other processes.

Continuing our program on the study of positive $K$ mesons, we have investigated the interactions of $K$ mesons with hydrogen and complex nuclei in photographic emulsions primarily in the energy interval 100 to 220 Mev. We are reporting on interactions found in 320 meters of ${K}^{+}$ track length followed, of which 227 meters were in the energy interval 100 to 220 Mev. The exposure was made to an enriched $K$-meson beam at the Berkeley Bevatron. The ratio of $K$ mesons to minimum ionizing background particles ranged from 1:1 to 1:3 across our stack. Thirteen new $K$-hydrogen scattering events were found and added to those previously published. We find the $K$-H cross section to be energy-independent in the energy interval from 20 to 200 Mev. The average cross section over this energy interval is 14.5\ifmmode\pm\else\textpm\fi{}2.2 mb. The differential cross section appears to be due predominantly to $S$-wave scattering.The data obtained on inelastic collisions with complex nuclei have been analyzed by using an independent-particle model for the nucleus. Using this model and correcting for (a) nucleon shading, (b) Coulomb repulsion, (c) Pauli exclusion principle, and (d) repulsive potentials, we obtained the average $K$-nucleon cross section as a function of energy. This cross section appears energy-independent in the energy interval 60 to 180 Mev. The values for the elementary cross sections obtained in this analysis for ${T}_{K}=60 \mathrm{to} 180$ Mev with $V={V}_{N}+{V}_{C}=35$ Mev were $\overline{\ensuremath{\sigma}}(\mathrm{the}\mathrm{average} K\ensuremath{-}\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{r}\mathrm{o}\mathrm{s}\mathrm{s}\phantom{\rule{0ex}{0ex}}\mathrm{s}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n})=11.8\ifmmode\pm\else\textpm\fi{}1.3$ mb, ${\ensuremath{\sigma}}_{\mathrm{KN}}=9.8\ifmmode\pm\else\textpm\fi{}3.0$ mb (with ${\ensuremath{\sigma}}_{\mathrm{Kn}}={{\ensuremath{\sigma}}_{n}}^{+}+{{\ensuremath{\sigma}}_{n}}^{0}$ where ${{\ensuremath{\sigma}}_{n}}^{+}$ is direct neutron scattering and ${{\ensuremath{\sigma}}_{n}}^{0}$ is charge-exchange scattering), ${{\ensuremath{\sigma}}_{n}}^{+}=5.8\ifmmode\pm\else\textpm\fi{}3.1$ mb, and ${{\ensuremath{\sigma}}_{n}}^{0}=4.0\ifmmode\pm\else\textpm\fi{}0.8$ mb. In this case the ratio ${\ensuremath{\sigma}}_{\mathrm{Kp}}:{{\ensuremath{\sigma}}_{n}}^{+}:{{\ensuremath{\sigma}}_{n}}^{0}\ensuremath{\approx}3.6:1.5:1$. We observe a backward peaking in the differential cross section and believe that this is due to a small $P$-wave contribution.These results lead us to believe that the $K$-nucleon scattering is a short-range force interaction and does not proceed through single $\ensuremath{\pi}$-meson exchange. The latter would require high-angular-momenta contributions and would presumably result in a strongly energy-dependent cross section.A repulsive potential was necessary to explain the behavior of the fractional energy loss as a function of energy. The magnitude of the potential necessary for a best fit $V\ensuremath{\approx}30$ Mev agrees very well with the results of a partial wave analysis of the elastic-scattering data.

In this paper we present, for five momenta from 864 to 1585 MeV/c, cross sections for stable final states and for resonance production, and an analysis of the KNπ Dalitz plots including the effects of K ∗ (891) − Δ(1236) interference. We see strong interference at all momenta where the K∗ is present, with the relative phase of the K∗N and KΔ amplitudes remaining constant as a function of momentum. We combine our cross-section results with those from other experiments to study the momentum dependence of the partial cross sections in the region of the 1250 MeV/c peak in the total cross section; we find that the total cross-section curve can be represented as the sum of partial cross-section curves, each one smooth and without a peak corresponding to that in the total cross section. Thus this structure is not due to structure in any single partial cross section, but rather to the sharp rises of the single- and double-pion-production channels at widely separated thresholds. This interpretation is at variance with a conventional resonance interpretation of the observed structure in the total cross section.

We present results on a search for S = 2 bosons in the final states K + K + ( I = 1), K 0 K + ( I = 1, I = 0) and KKnπ( π ⩾ 1) in a 9 GeV c K + p experiment. No statistically significant evidence for such resonances is observed in the mass region 1.0 to 3.1 GeV. The upper limit for the production cross section of the previously reported S = 2 enhancements at 1050 and 1280 MeV is estimated to be 1.5 and 2.0 μ, respectively.

Author(s): Goldhaber, Gerson; Goldhaber, Sulamith; Iloff, Edwin L.; Lannutti, Joseph E.; Webb, Francis H.; Widgoff, M.; Pevsner, A.; Ritson, D.