4,022 research outputs found
Single top quark measurements with CMS
Measurements of single top quark production are presented, performed using
CMS data collected in 2011 and 2012 at centre-of-mass energies of 7 and 8 TeV.
The cross sections for the electroweak production of single top quarks in the
t-channel and in association with W-bosons is measured and the results are used
to place constraints on the CKM matrix element |V_tb|.Comment: 5 pages, 6 figures, conference HCP201
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Tevatron top physics
A summary of the most recent results on top quark physics obtained at Fermilab's Tevatron proton-antiproton collider, operating at a centre of mass energy of 1.96 TeV, is presented. Measurements of the top pair and single top quark production cross sections, the investigation of top quark decay properties, the precision measurement of the top quark mass as well as searches for physics beyond the standard model are discussed
Adoptive immunotherapy against allogeneic kidney grafts in dogs with stable hematopoietic trichimerism.
Dogs given nonmyeloablative conditioning and marrow grafts from 2 dog leukocyte antigen (DLA)-identical littermate donors developed stable trichimerism and stably accepted a subsequent kidney graft from one of the marrow donors without the need for immunosuppression. In this study, we used trichimeras to evaluate strategies for adoptive immunotherapy to solid tumors, using the kidney as a tumor surrogate. Three DLA-identical trichimeric recipients were established by simultaneously infusing marrow from 2 DLA-identical donor dogs into a DLA-identical recipient conditioned with 2 Gy of total body irradiation (TBI) and given a short course of postgraft immunosuppression. After stable hematopoietic engraftment was confirmed, a kidney was transplanted from 1 of the 2 marrow donors into each respective trichimeric recipient. Peripheral blood lymphocytes from each kidney donor were then used to sensitize the alternate marrow donor. The trichimeric recipients were given donor lymphocyte infusions (DLIs) from the sensitized dogs and monitored for chimerism, graft-versus-host disease (GVHD), and kidney rejection. After DLI, we observed both prompt rejection of the transplanted marrow and donor kidney and disappearance of corresponding hematopoietic chimerism. Presumably due to shared minor histocompatibility antigens, host chimerism also disappeared, and GVHD in skin, gut, and liver developed. The native kidneys, although exhibiting lymphocytic infiltration, remained functionally normal. This study demonstrates that under certain experimental conditions, the kidney--an organ ordinarily not involved in graft-versus-host reactions--can be targeted by sensitized donor lymphocytes
An Intense Gamma-Ray Flare of PKS1622-297
We report the observation by the Compton Gamma Ray Observatory of a
spectacular flare of radio source PKS 1622-297. A peak flux of 17E-6 cm^-2 s^-1
(E > 100 MeV) was observed. The corresponding isotropic luminosity is 2.9E49
erg/s. We find that PKS 1622-297 exhibits gamma-ray intra-day variability. A
flux increase by a factor of at least 3.6 was observed to occur in less than
7.1 hours (with 99% confidence). Assuming an exponential rise, the
corresponding doubling time is less than 3.8 hours. A significant flux decrease
by a factor of ~2 in 9.7 hours was also observed. Without beaming, the rapid
flux change and large isotropic luminosity are inconsistent with the
Elliot-Shapiro condition (assuming that gas accretion is the immediate source
of power for the gamma-rays). This inconsistency suggests that the gamma-ray
emission is beamed. A minimum Doppler factor of 8.1 is implied by the observed
lack of pair-production opacity (assuming x-rays are emitted co-spatially with
the gamma-rays). Simultaneous observation by EGRET and OSSE finds a spectrum
adequately fit by a power law with photon index of -1.9. Although the
significance is not sufficient to establish this beyond doubt, the high-energy
gamma-ray spectrum appears to evolve from hard to soft as a flare progresses.Comment: 14 pages, 4 figures, 1 tabl
Search for Pair Production of Scalar Top Quarks Decaying to a tau Lepton and a b Quark in ppbar Collisions at sqrt{s}=1.96 TeV
We search for pair production of supersymmetric top quarks (~t_1), followed
by R-parity violating decay ~t_1 -> tau b with a branching ratio beta, using
322 pb^-1 of ppbar collisions at sqrt{s}=1.96 TeV collected by the CDF II
detector at Fermilab. Two candidate events pass our final selection criteria,
consistent with the standard model expectation. We set upper limits on the
cross section sigma(~t_1 ~tbar_1)*beta^2 as a function of the stop mass
m(~t_1). Assuming beta=1, we set a 95% confidence level limit m(~t_1)>153
GeV/c^2. The limits are also applicable to the case of a third generation
scalar leptoquark (LQ_3) decaying LQ_3 -> tau b.Comment: 7 pages, 2 eps figure
Search for and a measurement of the branching fraction for
We search for the decay and measure the
branching fraction for using
121.4~ of data collected at the
resonance with the Belle detector at the KEKB asymmetric-energy
collider. The branching fraction is measured
to be , where is the fraction of
in events. Our result is in good
agreement with the theoretical predictions as well as with a recent measurement
from LHCb. We observe no statistically significant signal for the decay
and set a confidence-level upper
limit on its branching fraction at . This constitutes a
significant improvement over the previous result.Comment: 6 pages, 3 figure
Measurements of the masses and widths of the and baryons
We present measurements of the masses and decay widths of the baryonic states
and using a data sample
corresponding to an integrated luminosity of 711 fb collected with the
Belle detector at the KEKB asymmetric-energy collider operating at
the resonance. We report the mass differences with respect to
the baryon MeV/, MeV/,
MeV/, MeV/, and the decay widths
MeV/,
MeV/,
MeV/,
MeV/,
where the first uncertainties are statistical and the second are systematic.
The isospin mass splittings are measured to be
MeV/ and
MeV/. These results are the most precise to date.Comment: 13 pages, 4 figures, Submitted to PRD(RC
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