Expectations for first single-top studies in CMS proton-proton collisions

We report on the expectations for first single top studies at the LHC with the CMS experiment. The Standard Model predicts the production of single top quark through three electroweak processes at LHC, referred to as t, s and tW channels. The t-channel has the highest cross section and the most potential for early observation. We describe the search strategy for the t-channel applied on a Monte Carlo sample at 10TeV p-p collision energy with an integrated luminosity of 200 pb−1 and on the expectations for the search of single top t-channel in the 7TeV scenario

The search for the single top at the LHC

We report on the predictions of the Standard Model for the single top-quark production at LHC and on the analysis strategies adopted by CMS and ATLAS for the single top-quark search. The Standard Model predicts the production of single top quark through three electroweak processes in the LHC energy reach, referred to as t, s and tW channels, resulting in distinct topologies and backgrounds. Different analysis strategies to search for the single top have been developed by CMS and ATLAS experiments. For the 14TeV center-of-mass energy scenario all the channels have been considered, while for the 10TeV scenario a specific strategy has been developed only for the t-channel and has been applied on Monte Carlo samples assuming an integrated luminosity of 200 pb−1

Gravitomagnetism and the Speed of Gravity

Experimental discovery of the gravitomagnetic fields generated by translational and/or rotational currents of matter is one of primary goals of modern gravitational physics. The rotational (intrinsic) gravitomagnetic field of the Earth is currently measured by the Gravity Probe B. The present paper makes use of a parametrized post-Newtonian (PN) expansion of the Einstein equations to demonstrate how the extrinsic gravitomagnetic field generated by the translational current of matter can be measured by observing the relativistic time delay caused by a moving gravitational lens. We prove that measuring the extrinsic gravitomagnetic field is equivalent to testing relativistic effect of the aberration of gravity caused by the Lorentz transformation of the gravitational field. We unfold that the recent Jovian deflection experiment is a null-type experiment testing the Lorentz invariance of the gravitational field (aberration of gravity), thus, confirming existence of the extrinsic gravitomagnetic field associated with orbital motion of Jupiter with accuracy 20%. We comment on erroneous interpretations of the Jovian deflection experiment given by a number of researchers who are not familiar with modern VLBI technique and subtleties of JPL ephemeris. We propose to measure the aberration of gravity effect more accurately by observing gravitational deflection of light by the Sun and processing VLBI observations in the geocentric frame with respect to which the Sun is moving with velocity 30 km/s.Comment: 16 pages, no figure

Phenomenology of the Lense-Thirring effect in the Solar System

Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde

Mass Screening in Modified Gravity

Models of modified gravity introduce extra degrees of freedom, which for consistency with the data, should be suppressed at observable scales. In the models that share properties of massive gravity such a suppression is due to nonlinear interactions: An isolated massive astrophysical object creates a halo of a nonzero curvature around it, shielding its vicinity from the influence of the extra degrees of freedom. We emphasize that the very same halo leads to a screening of the gravitational mass of the object, as seen by an observer beyond the halo. We discuss the case when the screening could be very significant and may rule out, or render the models observationally interesting.Comment: 16 pages, 4 figures, A contribution to the Proceedings of the International Workshop on Cosmology and Gravitation, Peyresq 12, June 16-22, 2007, Peyresq, Franc

Gravitomagnetism and Relative Observer Clock Effects

The gravitomagnetic clock effect and the Sagnac effect for circularly rotating orbits in stationary axisymmetric spacetimes are studied from a relative observer point of view, clarifying their relationships and the roles played by special observer families. In particular Semer\'ak's recent characterization of extremely accelerated observers in terms of the two-clock clock effect is shown to be complemented by a similarly special property of the single-clock clock effect.Comment: 19 pages, LaTeX, IOP macros with package epsf and 1 eps figure, to appear in Classical and Quantum Gravity, slight revisio

Efficacy of hemostatic powders as monotherapy or rescue therapy in gastrointestinal bleeding related to neoplastic or non-neoplastic lesions

Background Hemostatic powder (HP) in gastrointestinal bleeding (GIB) is mainly used as rescue therapy after failure of conventional hemostatic procedures (CHP). Aim To define the best field of application and the efficacy of HP as first choice monotherapy or rescue therapy. Methods We compared the efficacy of HP monotherapy, HP rescue therapy, and CHP in the management of active GIB due to neoplastic and non-neoplastic lesions. Results A total of 108 patients, 43 treated with HP as either first choice or rescue therapy and 65 with CHP, were included in the study. The most frequent sources of bleeding were peptic ulcer and malignancy. Immediate hemostasis rates were: HP monotherapy = 100% in peptic ulcer and 100% in malignancy; HP rescue therapy = 93.2% in peptic ulcer and 85.7% in malignancy; CHP = 77.9% in peptic ulcer and 41.7 in malignancy. Definitive hemostasis rates were: HP monotherapy = 50% in peptic ulcer and 45.5% in malignancy; HP rescue therapy = 73.3% in peptic ulcer and 85.7% in malignancy; CHP = 69.1% in peptic ulcer and 33.3% in malignancy. No difference was found in terms of additional intervention between the three groups. Conclusions HP is highly effective as monotherapy and rescue therapy in GIB. GIB related to malignancy may be the best field of application of HP, but confirmatory studies are necessary

Constraints from orbital motions around the Earth of the environmental fifth-force hypothesis for the OPERA superluminal neutrino phenomenology

It has been recently suggested by Dvali and Vikman that the superluminal neutrino phenomenology of the OPERA experiment may be due to an environmental feature of the Earth, naturally yielding a long-range fifth force of gravitational origin whose coupling with the neutrino is set by the scale M_*, in units of reduced Planck mass. Its characteristic length lambda should not be smaller than one Earth's radius R_e, while its upper bound is expected to be slightly smaller than the Earth-Moon distance (60 R_e). We analytically work out some orbital effects of a Yukawa-type fifth force for a test particle moving in the modified field of a central body. Our results are quite general since they are not restricted to any particular size of lambda; moreover, they are valid for an arbitrary orbital configuration of the particle, i.e. for any value of its eccentricity $e$. We find that the dimensionless strength coupling parameter alpha is constrained to |alpha| <= 1 10^-10-4 10^-9 for 1 R_e <= lambda <= 10 R_e by the laser data of the Earth's artificial satellite LAGEOS II, corresponding to M_* >= 4 10^9 -1.6 10^10. The Moon perigee allows to obtain |alpha| <= 3 10^-11 for the Earth-Moon pair in the range 15 R_e <= lambda = 3 10^10 - 4.5 10^10. Our results are neither necessarily limited to the superluminal OPERA scenario nor to the Dvali-Vikman model, in which it is M_* = 10^-6 at lambda = 1 R_e, in contrast with our bounds: they generally extend to any theoretical scenario implying a fifth-force of Yukawa-type.Comment: LaTex2e, 18 pages, 4 figures, 1 table, 81 reference

Heterochromatin characterization and ribosomal gene location in two monotypic genera of bloodsucker bugs (Cimicidae, Heteroptera) with holokinetic chromosomes and achiasmatic male meiosis

Abstract Members of the family Cimicidae (Heteroptera: Cimicomorpha) are temporary bloodsuckers on birds and bats as primary hosts and humans as secondary hosts. Acanthocrios furnarii (2n = 12 = 10 + XY, male) and Psitticimex uritui (2n = 31 = 28 + X 1 X 2 Y, male) are two monotypic genera of the subfamily Haematosiphoninae, which have achiasmatic male meiosis of collochore type. Here, we examined chromatin organization and constitution of cimicid holokinetic chromosomes by determining the amount, composition and distribution of constitutive heterochromatin, and number and location of nucleolus organizer regions (NORs) in both species. Results showed that these two bloodsucker bugs possess high heterochromatin content and have an achiasmatic male meiosis, in which three regions can be differentiated in each autosomal bivalent: (i) terminal heterochromatic regions in repulsion; (ii) a central region, where the homologous chromosomes are located parallel but without contact between them; and (iii) small areas within the central region, where collochores are detected. Acanthocrios furnarii presented a single NOR on an autosomal pair, whereas P. uritui presented two NORs, one on an autosomal pair and the other on a sex chromosome. All NORs were found to be associated with CMA 3 bright bands, indicating that the whole rDNA repeating unit is rich in G + C base pairs. Based on the variations in the diploid autosomal number, the presence of simple and multiple sex chromosome systems, and the number and location of 18S rDNA loci in the two Cimicidae species studied, we might infer that rDNA clusters and genome are highly dynamic among the representatives of this family