D0--anti-D0 mixing results from BaBar by analysis of D0 --> K+ pi- pi0 Dalitz-plot regions

We present a preliminary search for D0--anti-D0 mixing using the decays D0 --> K+ pi- pi0, additionally presenting Dalitz-plot distributions and a measurement of the branching ratio for this mode. A new tagging technique is used to produce the doubly Cabibbo-suppressed Dalitz plot, which in turn is used to motivate the method used for the D-mixing search. We analyze 230.4fb-1 of data collected from the BaBar detector at the PEP-II collider. Assuming CP conservation, we find R_M < 0.054% with 95% confidence, and we estimate that the data are consistent with no mixing at a 4.5% confidence level. We present D-mixing results both with and without the assumption of CP conservation.Comment: 5 pages, 5 figures, Flavor Physics & CP Violation Conference, Vancouver, 200

Network Economics and the Digital Divide in Rural South Asia

The concept of a 'global digital divide' is now common, and many cross-country studies of determinants of differences in computer and Internet penetration have been performed. The main conclusions and policy implications from these studies are relatively blunt: get richer, have more telephones, and regulate telecommunications better. In this paper, we examine an alternative approach to bridging the digital divide, through organizational innovations that provide low cost Internet access in developing countries, within the existing conditions of income levels, telecommunications infrastructure and regulatory environment. We use survey data from 500 individuals in three South Asian countries, Bangladesh, Nepal and Sri Lanka, to examine factors influencing patterns of computer and Internet use. These individuals were in situations where computer and Internet access has been provided by a developmental agency (government or non-government). We estimate logit and multinomial logit models, using explanatory variables such as income, household size, education, and occupation, as well as infrastructure factors such as quality of electricity supply, and availability of telephones and televisions. Thus we are able to go beyond simple analyses of penetration at the country level, to understand the microeconomics of computer and Internet use in rural South Asia

Network Economics and the Digital Divide in Rural India

The idea of a 'global digital divide' is well accepted, and cross-country studies of determinants of differences in computer and Internet penetration have identified income, telecommunications infrastructure, and regulatory quality as key influencing factors. The policy implications from these studies are relatively blunt: get richer, have more telephones, and regulate telecommunications better. In this paper, we examine an alternative policy approach to bridging the digital divide, through organizational innovations that provide low cost Internet access in developing countries, within the existing levels of income, telecommunications infrastructure and regulatory environment. We use survey data from 500 individuals in four states of India: Haryana, Madhya Pradesh, Punjab and Rajasthan, to examine factors influencing patterns of computer and Internet use. The situations in which data was collected were ones where computer and Internet access was being provided by a developmental agency (government or non-government). We estimate logit and multinomial logit models, using explanatory variables such as income, household size, education, and occupation, as well as infrastructure factors such as quality of electricity supply, and availability of telephones and televisions. Thus we are able to go beyond simple analyses of penetration at the country level, to understand the microeconomics of computer and Internet use in rural India. In particular, by examining patterns of use, we are able to comment on the importance of network externalities for diffusion of computers and the Internet in these local rural contexts

The Gamma-ray Albedo of the Moon

We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalisation; this makes it a useful "standard candle" for gamma-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo gamma-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo gamma rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.Comment: 6 pages, 4 figures, emulateapj.cls; to appear in the Astrophysical Journa

Tevatron searches for Higgs bosons beyond the standard model

Theoretical frameworks beyond the standard model predict a rich Higgs sector with multiple charged and neutral Higgs bosons. Both the CDF II and D0 experiments at the Tevatron have analyzed 1 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96TeV in search of Higgs boson production. A complete suite of results on searches for neutral, charged, and fermiophobic Higgs bosons limit the allowed production rates and constrain extended models, including the minimal supersymmetric standard model

Studies of Rare Hadronic B Decays with BaBar

We present a selection of recent results from studies of rare hadronic B decays based on a sample of 232 million B{bar B} pairs, corresponding to an integrated luminosity of 211 fb{sup -1}, which were recorded with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring

Electronics for Satellite Experiments

The tracking detector for the LAT science instrument on the GLAST mission is an example of a large-scale particle detection system built primarily by particle physicists for space flight within the context of a NASA program. The design and fabrication model in most ways reflected practice and experience from particle physics, but the quality assurance aspects were guided by NASA. Similarly, most of the electronics in the LAT as a whole were designed and built by staff at a particle physics lab. This paper reports on many of the challenges and lessons learned in the experience of designing and building the tracking detector and general LAT electronics for use in the NASA GLAST mission

A Search for Direct CP Violation in Two-Body Cabibbo-Suppressed Decays of Neutral Charmed Mesons

Presented are the results of a search for direct CP violation in Cabibbo-suppressed decays of D{sup 0} to two charged daughters. The analysis described was performed on {approx}230 fb{sup -1} of the BABAR data sample, recorded at the Stanford Linear Accelerator Center and using the PEP-II electron storage rings. We measure CP asymmetries for decay to the KK and {pi}{pi} final states, as well as for the branching ratio, and develop a new technique for tagging-efficiency correction using the Cabibbo-favored K{pi} final state. We find some evidence for CP violation in decays to the KK final state and results that suggest CP violation in the {pi}{pi} final state as well

Fallback and Black Hole Production in Massive Stars

The compact remnants of core collapse supernovae--neutron stars and black holes--have properties that reflect both the structure of their stellar progenitors and the physics of the explosion. In particular, the masses of these remnants are sensitive to the density structure of the presupernova star and to the explosion energy. To a considerable extent, the final mass is determined by the ''fallback'', during the explosion, of matter that initially moves outwards, yet ultimately fails to escape. We consider here the simulated explosion of a large number of massive stars (10 to 100 M{sub {circle_dot}}) of Population I (solar metallicity) and III (zero metallicity), and find systematic differences in the remnant mass distributions. As pointed out by Chevalier (1989), supernovae in more compact progenitor stars have stronger reverse shocks and experience more fallback. For Population III stars above about 25 M{sub {circle_dot}} and explosion energies less than 1.5 x 10{sup 51} erg, black holes are a common outcome, with masses that increase monotonically with increasing main sequence mass up to a maximum hole mass of about 35 M{sub {circle_dot}}. If such stars produce primary nitrogen, however, their black holes are systematically smaller. For modern supernovae with nearly solar metallicity, black hole production is much less frequent and the typical masses, which depend sensitively on explosion energy, are smaller. We explore the neutron star initial mass function for both populations and, for reasonable assumptions about the initial mass cut of the explosion, find good agreement with the average of observed masses of neutron stars in binaries. We also find evidence for a bimodal distribution of neutron star masses with a spike around 1.2 M{sub {circle_dot}} (gravitational mass) and a broader distribution peaked around 1.4 M{sub {circle_dot}}

Definition of a Twelve-Point Polygonal SAA Boundaryfor the GLAST Mission

The Gamma-Ray Large Area Space Telescope (GLAST), set to launch in early 2008, detects gamma rays within a huge energy range of 100 MeV - 300 GeV. Background cosmic radiation interferes with such detection resulting in confusion over distinguishing cosmic from gamma rays encountered. This quandary is resolved by encasing GLAST's Large Area Telescope (LAT) with an Anti-Coincidence Detector (ACD), a device which identifies and vetoes charged particles. The ACD accomplishes this through plastic scintillator tiles; when cosmic rays strike, photons produced induce currents in Photomultiplier Tubes (PMTs) attached to these tiles. However, as GLAST orbits Earth at altitudes {approx}550km and latitudes between -26 degree and 26 degree, it will confront the South Atlantic Anomaly (SAA), a region of high particle flux caused by trapped radiation in the geomagnetic field. Since the SAA flux would degrade the sensitivity of the ACD's PMTs over time, a determined boundary enclosing this region need be attained, signaling when to lower the voltage on the PMTs as a protective measure. The operational constraints on such a boundary require a convex SAA polygon with twelve edges, whose area is minimal ensuring GLAST has maximum observation time. The AP8 and PSB97 models describing the behavior of trapped radiation were used in analyzing the SAA and defining a convex SAA boundary of twelve sides. The smallest possible boundary was found to cover 14.58% of GLAST's observation time. Further analysis of defining a boundary safety margin to account for inaccuracies in the models reveals if the total SAA hull area is increased by {approx}20%, the loss of total observational area is &lt; 5%. These twelve coordinates defining the SAA flux region are ready for implementation by the GLAST satellite