Maxwell's field coupled nonminimally to quadratic torsion: Induced axion field and birefringence of the vacuum

We consider a possible (parity conserving) interaction between the electromagnetic field $F$ and a torsion field $T^\alpha$ of spacetime. For generic elementary torsion, gauge invariant coupling terms of lowest order fall into two classes that are both nonminimal and {\it quadratic} in torsion. These two classes are displayed explicitly. The first class of the type $\sim F T^2$ yields (undesirable) modifications of the Maxwell equations. The second class of the type $\sim F^2 T^2$ doesn't touch the Maxwell equations but rather modifies the constitutive tensor of spacetime. Such a modification can be completely described in the framework of metricfree electrodynamics. We recognize three physical effects generated by the torsion: (i) An axion field that induces an {\em optical activity} into spacetime, (ii) a modification of the light cone structure that yields {\em birefringence} of the vacuum, and (iii) a torsion dependence of the {\em velocity of light.} We study these effects in the background of a Friedmann universe with torsion. {\it File tor17.tex, 02 August 2003}Comment: 6 page

RGDS peptides immobilized on titanium alloy stimulate bone cell attachment, differentiation and confer resistance to apoptosis

A major cause of implant failure in skeletal tissues is failure of osseointegration, often due to lack of adhesion of cells to the titanium (Ti) alloy interface. Since arginine- glycine-aspartic acid (RGD)-containing peptides have been shown to regulate osteoblast adhesion, we tested the hypothesis that, bound to a Ti surface, these peptides would promote osteoblasts differentiation, while at the same time inhibit apoptosis. RGDS and RGES (control) peptides were covalently linked to Ti discs using an APTS linker. While the grafting of both RGDS and RGES significantly increased Ti surface roughness, contact angle analysis showed that APTS significantly increased the surface hydrophobicity; when the peptides were tethered to Ti, this was reduced. To evaluate attachment, MC3T3-E1 osteoblast cells were grown on these discs. Significantly more cells attached to the Ti-grafted RGDS then the Ti-grafted RGES control. Furthermore, expression of the osteoblasts phenotype was significantly enhanced on the Ti-grafted RGDS surface. When cells attached to the Ti-grafted RGDS were challenged with staurosporine, an apoptogen, there was significant inhibition of apoptosis; in contrast, osteoblasts adherent to the Ti-grafted RGES were killed. It is concluded that RGD-containing peptides covalently bonded to Ti promotes osteoblasts attachment and survival with minimal changes to the surface of the alloy. Therefore, such modifications to Ti would have the potential to promote osseointegration in vivo

Spectrum of pheochromocytoma in the 131 I-MIBG era

131 I-metaiodobenzylguanidine ( 131 I-MIBG) scintigraphy allows for both functional diagnosis and anatomical localization of pheochromocytoma. The spectrum of pheochromocytoma since the routine use of preoperative 131 I-MIBG scan was studied. From 1980 to 1986, a total of 34 patients were primarily diagnosed and treated at the University of Michigan Medical Center, Ann Arbor, Michigan, U.S.A. There were 16 males and 18 females. The mean age was 38 years and 4 patients (11.8%) were under 18 years of age. Six patients (17.6%) had family history of pheochromocytoma or multiple endocrine neoplasia (MEN) II syndrome. The presenting symptoms were hypertension in 29 patients (85.3%); attacks of headache, palpitation, sweating, and flushing in 4 (11.8%), and 1 patient presented with a neck mass. Plasma catecholamines were elevated in 97% of patients while urinary catecholamines and metabolites were elevated in 93.5%. 131 I-MIBG was accurate in 82.3%, partly positive in 11.8%, and false-negative in 5.9% of patients. CT scan was accurate in 80%, partly positive in 10%, but failed to show the tumor in another 10% of patients. At operation, extraadrenal lesions were found in 38.2% of the patients and among these, one-third were extraabdominal. Multiple tumors occurred in 5 (14.7%), and bilateral adrenal lesions occurred in 4 patients (11.8%). Malignancy was diagnosed in 3 patients (8.8%) after an average follow-up period of 2 years. We conclude that the use of routine preoperative 131 I-MIBG scanning improves localization of pheochromocytoma and earlier diagnosis is possible in patients with MEN II syndrome. Multiple tumors, extraadrenal and extraabdominal lesions occur more often than commonly believed. The low rate of confirmed malignancy is probably related to the short period of follow-up. La scintigraphie à l' 131 I-MIBG permet de diagnostiquer et de localiser les phéochromocytomes. Toute la gamme de types de phéochromocytomes reconnu depuis l'utilisation préopératoire systématique de la scintigraphie à l' 131 I-MIBG est présentée. Entre 1980 et 1986, 34 patients ont été explorés et traités au Centre Médical de l'Université de Michigan, Ann Arbor, Michigan. Il y avait 16 hommes et 18 femmes. L'âge moyen était de 38 ans, et 4 patients (11.8%) avaient moins de 18 ans. Six patients (17.6%) avaient des antécédents familiaux de phéochromocytome ou de néoplasmes endocrines multiples (MEN) du type II. Les symptômes amenant à consulter étaient l'hypertension chez 29 patients (85.3%), des crises de céphalées, des palpitations et un flush chez 4 patients (11.8%); un patient présentait une masse cervicale. Les catécholamines plasmatiques étaient élevées chez 97% des patients alors que les catécholamines et leurs métabolites étaient en quantité élevée chez 93.5% des patients. La scintigraphie à l' 131 I-MIBG était positive chez 82.3%, partiellement positive chez 11.8%, et faussement négative chez 5.9% des patients. La tomodensitométrie était positive chez 80%, partiellement positive chez 10%, et faussement négative chez 10% des patients. A l'intervention, des lésions extra-surrénales étaient présentes dans 38.2% des cas, et parmi celles-ci, un tiers étaient extra-abdominales. Les tumeurs étaient multiples dans 5 cas (14.7%), et bilatérales surrénales dans 4 cas (11.8%). Une tumeur maligne était diagnostiquée chez 3 patients (8.8%), après une période de suivi de 2 ans en moyenne. Nous concluons que l'utilisation systématique de la scintigraphie à l' 131 I-MIBG améliore la localisation des phéochromocytomes, permettant un diagnostic plus précoce chez les patients présentant un syndrome MEN II. La multiplicité tumorale et les localisations extra-médullosurrénales ou extra-abdominales se voient beaucoup plus fréquemment qu'on le pensait auparavant. Le taux de malignité peu élevé était probablement en rapport avec la courte période de suivi. La escintigrafía con 131 I-MIBG permite tanto la localización anatómica como el diagnóstico funcional del feocromocitoma. Las características o espectro del feocromocitoma a partir del uso rutinario de 131 I-MIBG han sido estudiadas.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41282/1/268_2005_Article_BF01655447.pd

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review