356 research outputs found
Attaining a record level of copper-wire properties by using SPD methods
A new approach is proposed to control the processes of plastic deformation of materials by the methods of severe plastic deformation (SPD). High strength and plasticity have been attained for the processed copper billets after multiple repetitions of angular hydroextrusion (ECAH) and hydroextrusion (HE) methods and with ECAH and HE implementation in the fractional mode. The combined severe plastic deformation technology including ECAH, HE and drawing (D) provided the ultimate tensile strength σ = 686 MPa, the elongation to failure δ = 2% and the electrical conductivity at a level of 86.4% IACS in the 0.5 mm diameter copper wire. Such a processing is efficient due to the alternating schemes of deformation and periodic creation of favorable conditions for relaxation and dynamic recrystallization processes in the material. An important condition for the attaining of the maximum processing effect is the fractional mode and the optimum degree of deformation by the both methods.Предложен новый подход к управлению процессами пластической деформации материалов при обработке заготовок методами интенсивной пластической деформации (ИПД). Высокий комплекс прочности и пластичности обработанных медных заготовок получен после многократного чередования методов угловой гидроэкструзии (УГЭ) и прямой гидроэкструзии (ГЭ) с реализацией УГЭ и ГЭ в дробном режиме. Комбинированная ИПД-технология, включающая УГЭ, ГЭ и волочение (В), обеспечивает в медной проволоке диаметром 0.5 mm предел прочности σ = 686 MPa, относительное удлинение δ = 2% и электрическую проводимость на уровне 86.4% IACS. Эффект такой обработки обусловлен чередованием схем деформаций и периодическим обеспечением благоприятных условий для протекания в материале процессов релаксации и динамической рекристаллизации. Важным условием достижения максимального эффекта обработки являются дробный режим и оптимальные степени деформации обоими методами.Запропоновано новий підхід до керування процесами пластичної деформації матеріалів при обробці заготовок методами інтенсивної пластичної деформації (ІПД). Високий комплекс міцності й пластичності оброблених мідних заготовок отриманий після багаторазового чергування методів кутової гідроекструзії (КГЕ) і прямої гідроекструзії (ГЕ) з реалізацією КГЕ й ГЕ в дробовому режимі. Комбінована ІПД-технологія, що включає КГЕ, ГЕ й волочіння (В), забезпечує в мідному дроті діаметром 0.5 mm межу міцності σ = 686 MPa, відносне подовження δ = 2% і електричну провідність на рівні 86.4% IACS. Ефект такої обробки обумовлений чергуванням схем деформацій і періодичним забезпеченням сприятливих умов для протікання в матеріалі процесів релаксації й динамічної рекристалізації. Важливою умовою досягнення максимального ефекту обробки є дробовий режим і оптимальні ступені деформації обома методами
Current correlators to all orders in the quark masses
The contributions to the coefficient functions of the quark and the mixed
quark-gluon condensate to mesonic correlators are calculated for the first time
to all orders in the quark masses, and to lowest order in the strong coupling
constant. Existing results on the coefficient functions of the unit operator
and the gluon condensate are reviewed. The proper factorization of short- and
long-distance contributions in the operator product expansion is discussed in
detail. It is found that to accomplish this task rigorously the operator
product expansion has to be performed in terms of non-normal-ordered
condensates. The resulting coefficient functions are improved with the help of
the renormalization group. The scale invariant combination of dimension 5
operators, including mixing with the mass operator, which is needed for the
renormalization group improvement, is calculated in the leading order.Comment: 24 pages, LateX file, TUM-T31-21/92, 1 postscript file include
Elliptic hypergeometry of supersymmetric dualities II. Orthogonal groups, knots, and vortices
We consider Seiberg electric-magnetic dualities for 4d SYM
theories with SO(N) gauge group. For all such known theories we construct
superconformal indices (SCIs) in terms of elliptic hypergeometric integrals.
Equalities of these indices for dual theories lead both to proven earlier
special function identities and new conjectural relations for integrals. In
particular, we describe a number of new elliptic beta integrals associated with
the s-confining theories with the spinor matter fields. Reductions of some
dualities from SP(2N) to SO(2N) or SO(2N+1) gauge groups are described.
Interrelation of SCIs and the Witten anomaly is briefly discussed. Possible
applications of the elliptic hypergeometric integrals to a two-parameter
deformation of 2d conformal field theory and related matrix models are
indicated. Connections of the reduced SCIs with the state integrals of the knot
theory, generalized AGT duality for (3+3)d theories, and a 2d vortex partition
function are described.Comment: Latex, 58 pages; paper shortened, to appear in Commun. Math. Phy
A Phenomenological Analysis of Gluon Mass Effects in Inclusive Radiative Decays of the and $\Upsilon
The shapes of the inclusive photon spectra in the processes \Jp \to \gamma
X and \Up \to \gamma X have been analysed using all available experimental
data.
Relativistic, higher order QCD and gluon mass corrections were taken into
account in the fitted functions. Only on including the gluon mass corrections,
were consistent and acceptable fits obtained. Values of
GeV and GeV were found for the
effective gluon masses (corresponding to Born level diagrams) for the \Jp and
\Up respectively. The width ratios \Gamma(V \to {\rm hadrons})/\Gamma(V \to
\gamma+ {\rm hadrons}) V=\Jp, \Up were used to determine and . Values consistent with the current world
average were obtained only when gluon mass correction factors,
calculated using the fitted values of the effective gluon mass, were applied. A
gluon mass GeV, as suggested with these results, is consistent with
previous analytical theoretical calculations and independent phenomenological
estimates, as well as with a recent, more accurate, lattice calculation of the
gluon propagator in the infra-red region.Comment: 50 pages, 11 figures, 15 table
Measurement of the J/Psi Production Cross Section in 920 GeV/c Fixed-Target Proton-Nucleus Interactions
The mid-rapidity (dsigma_(pN)/dy at y=0) and total sigma_(pN) production
cross sections of J/Psi mesons are measured in proton-nucleus interactions.
Data collected by the HERA-B experiment in interactions of 920 GeV/c protons
with carbon, titanium and tungsten targets are used for this analysis. The
J/Psi mesons are reconstructed by their decay into lepton pairs. The total
production cross section obtained is sigma_(pN)(J/Psi) = 663 +- 74 +- 46
nb/nucleon. In addition, our result is compared with previous measurements
In-medium operator product expansion for heavy-light-quark pseudoscalar mesons
The operator product expansion (OPE) for heavy-light-quark pseudoscalar
mesons (D-mesons and B-mesons) in medium is determined, both for a moving meson
with respect to the surrounding medium as well as for a meson at rest. First of
all, the OPE is given in terms of normal-ordered operators up to mass dimension
5, and the mass of the heavy-quark and the mass of the light-quark are kept
finite. The Wilson coefficients of such an expansion are infrared (IR)
divergent in the limit of a vanishing light-quark mass. A consistent separation
of scales necessitates an OPE in terms of non-normal-ordered operators, which
implies operator mixing, where the IR-divergences are absorbed into the
operators. It is shown that the Wilson coefficients of such an expansion are
IR-stable, and the limit of a vanishing light-quark mass is perfomed. Details
of the major steps for the calculation of the Wilson coefficients are
presented. By a comparison with previous results obtained by other theoretical
groups we have found serious disagreements.Comment: 51 pages, 3 figure
Search for the Flavor-Changing Neutral Current Decay with the HERA-B Detector
We report on a search for the flavor-changing neutral current decay using events recorded with a dimuon trigger in
interactions of 920 GeV protons with nuclei by the HERA-B experiment. We find
no evidence for such decays and set a 90% confidence level upper limit on the
branching fraction .Comment: 17 pages, 4 figures (of which 1 double), paper to be submitted to
Physics Letters
Measurement of (anti)deuteron and (anti)proton production in DIS at HERA
The first observation of (anti)deuterons in deep inelastic scattering at HERA
has been made with the ZEUS detector at a centre-of-mass energy of 300--318 GeV
using an integrated luminosity of 120 pb-1. The measurement was performed in
the central rapidity region for transverse momentum per unit of mass in the
range 0.3<p_T/M<0.7. The particle rates have been extracted and interpreted in
terms of the coalescence model. The (anti)deuteron production yield is smaller
than the (anti)proton yield by approximately three orders of magnitude,
consistent with the world measurements.Comment: 26 pages, 9 figures, 5 tables, submitted to Nucl. Phys.
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
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