Rubin-LSST

Abstract:

We have searched for flavor-changing neutral current decays and lepton-number-violating decays of D⁺ and Ds+ mesons to final states of the form h^±e e⁺, where h is either π or K. We use the complete samples of CLEO-c open-charm data, corresponding to integrated luminosities of 818pb^-1 at the center-of-mass energy E CM=3.774GeV containing 2.4×106 D⁺D^- pairs and 602pb^-1 at ECM=4.170GeV containing 0.6×106 Ds*±Ds pairs. No signal is observed in any channel, and we obtain 90% confidence level upper limits on branching fractions B(D ⁺→π⁺e⁺e^-)<5. 9×10^-6, B(D⁺→π^-e ⁺e⁺)<1.1×10^-6, B(D⁺→ K⁺e⁺e^-)<3.0×10^-6, B(D ⁺→K^-e⁺e⁺)<3.5×10 ^-6, B(Ds+→π⁺e⁺e^-)<2. 2×10^-5, B(Ds+→π^-e⁺e ⁺)<1.8×10^-5, B(Ds+→K⁺e ⁺e^-)<5.2×10^-5, and B(Ds+→K ^-e⁺e⁺)<1.7×10^-5. © 2010 The American Physical Society.

Abstract:

Galaxy formation is significantly modulated by energy output from supermassive black holes at the centers of galaxies which grow in highly efficient luminous quasar phases. The timescale on which black holes transition into and out of such phases is, however, unknown. We present the first measurement of the shutdown timescale for an individual quasar using X-ray observations of the nearby galaxy IC 2497, which hosted a luminous quasar no more than 70,000 years ago that is still seen as a light echo in "Hanny's Voorwerp," but whose present-day radiative output is lower by at least two, and more likely by over four, orders of magnitude. This extremely rapid shutdown provides new insight into the physics of accretion in supermassive black holes and may signal a transition of the accretion disk to a radiatively inefficient state. © 2010. The American Astronomical Society. All rights reserved.

Abstract:

Recent searches by unbiased, wide-field surveys have uncovered a group of extremely luminous optical transients. The initial discoveries of SN 2005ap by the Texas Supernova Search and SCP-06F6 in a deep Hubble pencil beam survey were followed by the Palomar Transient Factory confirmation of host redshifts for other similar transients. The transients share the common properties of high optical luminosities (peak magnitudes ∼ -21 to -23), blue colors, and a lack of H or He spectral features. The physical mechanism that produces the luminosity is uncertain, with suggestions ranging from jet-driven explosion to pulsational pair instability. Here, we report the most detailed photometric and spectral coverage of an ultra-bright transient (SN 2010gx) detected in the Pan-STARRS 1 sky survey. In common with other transients in this family, early-time spectra show a blue continuum and prominent broad absorption lines of OII. However, about 25 days after discovery, the spectra developed type Ic supernova features, showing the characteristic broad FeII and Si II absorption lines. Detailed, post-maximum follow-up may show that all SN 2005ap and SCP-06F6 type transients are linked to supernovae Ic. This poses problems in understanding the physics of the explosions: there is no indication from late-time photometry that the luminosity is powered by ⁵⁶Ni, the broad light curves suggest very large ejected masses, and the slow spectral evolution is quite different from typical Ic timescales. The nature of the progenitor stars and the origin of the luminosity are intriguing and open questions. © 2010. The American Astronomical Society. All rights reserved.

Abstract:

A search for narrow resonances in the dijet mass spectrum is performed using data corresponding to an integrated luminosity of 2.9pb⊃-1 collected by the CMS experiment at the Large Hadron Collider. Upper limits at the 95% confidence level are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, or gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% confidence level: string resonances, with mass less than 2.50 TeV, excited quarks, with mass less than 1.58 TeV, and axigluons, colorons, and E6 diquarks, in specific mass intervals. This extends previously published limits on these models. Copyright © 2010 American Physical Society.