3,040 research outputs found
Baryonic Bound State of Vortices in Multicomponent Superconductors
We construct a bound state of three 1/3-quantized Josephson coupled vortices
in three-component superconductors with intrinsic Josephson couplings, which
may be relevant with regard to iron-based superconductors. We find a Y-shaped
junction of three domain walls connecting the three vortices, resembling the
baryonic bound state of three quarks in QCD. The appearance of the Y-junction
(but not a Delta-junction) implies that in both cases of superconductors and
QCD, the bound state is described by a genuine three-body interaction (but not
by the sum of two-body interactions). We also discuss a
confinement/deconfinement phase transition.Comment: 11 pages, 3 figures, one section on confinement/deconfinement
transition added, published versio
Measurement of Resonance Parameters of Orbitally Excited Narrow B^0 Mesons
We report a measurement of resonance parameters of the orbitally excited
(L=1) narrow B^0 mesons in decays to B^{(*)+}\pi^- using 1.7/fb of data
collected by the CDF II detector at the Fermilab Tevatron. The mass and width
of the B^{*0}_2 state are measured to be m(B^{*0}_2) =
5740.2^{+1.7}_{-1.8}(stat.) ^{+0.9}_{-0.8}(syst.) MeV/c^2 and \Gamma(B^{*0}_2)
= 22.7^{+3.8}_{-3.2}(stat.) ^{+3.2}_{-10.2}(syst.) MeV/c^2. The mass difference
between the B^{*0}_2 and B^0_1 states is measured to be
14.9^{+2.2}_{-2.5}(stat.) ^{+1.2}_{-1.4}(syst.) MeV/c^2, resulting in a B^0_1
mass of 5725.3^{+1.6}_{-2.2}(stat.) ^{+1.4}_{-1.5}(syst.) MeV/c^2. This is
currently the most precise measurement of the masses of these states and the
first measurement of the B^{*0}_2 width.Comment: 7 pages, 1 figure, 1 table. Submitted to Phys.Rev.Let
Measurement of the fraction of t-tbar production via gluon-gluon fusion in p-pbar collisions at sqrt(s)=1.96 TeV
We present a measurement of the ratio of t-tbar production cross section via
gluon-gluon fusion to the total t-tbar production cross section in p-pbar
collisions at sqrt{s}=1.96 TeV at the Tevatron. Using a data sample with an
integrated luminosity of 955/pb recorded by the CDF II detector at Fermilab, we
select events based on the t-tbar decay to lepton+jets. Using an artificial
neural network technique we discriminate between t-tbar events produced via
q-qbar annihilation and gluon-gluon fusion, and find
Cf=(gg->ttbar)/(pp->ttbar)<0.33 at the 68% confidence level. This result is
combined with a previous measurement to obtain the most precise measurement of
this quantity, Cf=0.07+0.15-0.07.Comment: submitted to Phys. Rev.
Symmetry and Topology in Superconductors - Odd-frequency pairing and edge states -
Superconductivity is a phenomenon where the macroscopic quantum coherence
appears due to the pairing of electrons. This offers a fascinating arena to
study the physics of broken gauge symmetry. However, the important symmetries
in superconductors are not only the gauge invariance. Especially, the symmetry
properties of the pairing, i.e., the parity and spin-singlet/spin-triplet,
determine the physical properties of the superconducting state. Recently it has
been recognized that there is the important third symmetry of the pair
amplitude, i.e., even or odd parity with respect to the frequency. The
conventional uniform superconducting states correspond to the even-frequency
pairing, but the recent finding is that the odd-frequency pair amplitude arises
in the spatially non-uniform situation quite ubiquitously. Especially, this is
the case in the Andreev bound state (ABS) appearing at the surface/interface of
the sample. The other important recent development is on the nontrivial
topological aspects of superconductors. As the band insulators are classified
by topological indices into (i) conventional insulator, (ii) quantum Hall
insulator, and (iii) topological insulator, also are the gapped
superconductors. The influence of the nontrivial topology of the bulk states
appears as the edge or surface of the sample. In the superconductors, this
leads to the formation of zero energy ABS (ZEABS). Therefore, the ABSs of the
superconductors are the place where the symmetry and topology meet each other
which offer the stage of rich physics. In this review, we discuss the physics
of ABS from the viewpoint of the odd-frequency pairing, the topological
bulk-edge correspondence, and the interplay of these two issues. It is
described how the symmetry of the pairing and topological indices determines
the absence/presence of the ZEABS, its energy dispersion, and properties as the
Majorana fermions.Comment: 91 pages, 38 figures, Review article, references adde
Search for lepton flavor violating decays of a heavy neutral particle in p-pbar collisions at root(s)=1.8 TeV
We report on a search for a high mass, narrow width particle that decays
directly to e+mu, e+tau, or mu+tau. We use approximately 110 pb^-1 of data
collected with the Collider Detector at Fermilab from 1992 to 1995. No evidence
of lepton flavor violating decays is found. Limits are set on the production
and decay of sneutrinos with R-parity violating interactions.Comment: Figure 2 fixed. Reference 4 fixed. Minor changes to tex
Phase transition in spin systems with various types of fluctuations
Various types ordering processes in systems with large fluctuation are overviewed. Generally, the so-called order–disorder phase transition takes place in competition between the interaction causing the system be ordered and the entropy causing a random disturbance. Nature of the phase transition strongly depends on the type of fluctuation which is determined by the structure of the order parameter of the system. As to the critical property of phase transitions, the concept “universality of the critical phenomena” is well established. However, we still find variety of features of ordering processes. In this article, we study effects of various mechanisms which bring large fluctuation in the system, e.g., continuous symmetry of the spin in low dimensions, contradictions among interactions (frustration), randomness of the lattice, quantum fluctuations, and a long range interaction in off-lattice systems
Effect of transport-induced charge inhomogeneity on point-contact Andreev reflection spectra at ferromagnet-superconductor interfaces
We investigate the transport properties of a ferromagnet-superconductor
interface within the framework of a modified three-dimensional
Blonder-Tinkham-Klapwijk formalism. In particular, we propose that charge
inhomogeneity forms via two unique transport mechanisms, namely, evanescent
Andreev reflection and evanescent quasiparticle transmission. Furthermore, we
take into account the influence of charge inhomogeneity on the interfacial
barrier potential and calculate the conductance as a function of bias voltage.
Point-contact Andreev reflection (PCAR) spectra often show dip structures,
large zero-bias conductance enhancement, and additional zero-bias conductance
peak. Our results indicate that transport-induced charge inhomogeneity could be
a source of all these anomalous characteristics of the PCAR spectra.Comment: 9 pages, 6 figure
Molecular biology of histidine decarboxylase and prostaglandin receptors
Histamine and prostaglandins (PGs) play a variety of physiological roles as autacoids, which function in the vicinity of their sources and maintain local homeostasis in the body. They stimulate target cells by acting on their specific receptors, which are coupled to trimeric G proteins. For the precise understanding of the physiological roles of histamine and PGs, it is necessary to clarify the molecular mechanisms involved in their synthesis as well as their receptor-mediated responses. We cloned the cDNAs for mouse l-histidine decarboxylase (HDC) and 6 mouse prostanoid receptors (4 PGE2 receptors, PGF receptor, and PGI receptor). We then characterized the expression patterns and functions of these genes. Furthermore, we established gene-targeted mouse strains for HDC and PG receptors to explore the novel pathophysiological roles of histamine and PGs. We have here summarized our research, which should contribute to progress in the molecular biology of HDC and PG receptors
Search for a Higgs Boson Decaying to Two W Bosons at CDF
We present a search for a Higgs boson decaying to two W bosons in ppbar collisions at sqrt(s)=1.96 TeV center-of-mass energy. The data sample corresponds to an integrated luminosity of 3.0 fb-1 collected with the CDF II detector. We find no evidence for production of a Higgs boson with mass between 110 and 200 GeV/c^2, and determine upper limits on the production cross section. For the mass of 160 GeV/c^2, where the analysis is most sensitive, the observed (expected) limit is 0.7 pb (0.9 pb) at 95% Bayesian credibility level which is 1.7 (2.2) times the standard model cross section
Top Quark Mass Measurement in the Lepton plus Jets Channel Using a Modified Matrix Element Method
46 pages, 16 figures. Edited in response to referee comments and resubmitted to Phys. Rev. DWe report a measurement of the top quark mass, m_t, obtained from ppbar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9 fb^-1. We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, with effective propagators to take into account assumptions on event kinematics. Our event likelihood is a function of m_t and a parameter JES that determines /in situ/ the calibration of the jet energies. We use a neural network discriminant to distinguish signal from background events. We also apply a cut on the peak value of each event likelihood curve to reduce the contribution of background and badly reconstructed events. Using the 318 events that pass all selection criteria, we find m_t = 172.7 +/- 1.8 (stat. + JES) +/- 1.2 (syst.) GeV/c^2.We report a measurement of the top quark mass, mt, obtained from pp̅ collisions at √s=1.96 TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9 fb-1. We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, where the matrix element is modified by using effective propagators to take into account assumptions on event kinematics. Our event likelihood is a function of mt and a parameter JES (jet energy scale) that determines in situ the calibration of the jet energies. We use a neural network discriminant to distinguish signal from background events. We also apply a cut on the peak value of each event likelihood curve to reduce the contribution of background and badly reconstructed events. Using the 318 events that pass all selection criteria, we find mt=172.7±1.8(stat+JES)±1.2(syst) GeV/c2.Peer reviewe
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