98 research outputs found
Selfsimilarity and growth in Birkhoff sums for the golden rotation
We study Birkhoff sums S(k,a) = g(a)+g(2a)+...+g(ka) at the golden mean
rotation number a with periodic continued fraction approximations p(n)/q(n),
where g(x) = log(2-2 cos(2 pi x). The summation of such quantities with
logarithmic singularity is motivated by critical KAM phenomena. We relate the
boundedness of log- averaged Birkhoff sums S(k,a)/log(k) and the convergence of
S(q(n),a) with the existence of an experimentally established limit function
f(x) = lim S([x q(n)])(p(n+1)/q(n+1))-S([x q(n)])(p(n)/q(n)) for n to infinity
on the interval [0,1]. The function f satisfies a functional equation f(ax) +
(1-a) f(x)= b(x) with a monotone function b. The limit lim S(q(n),a) for n
going to infinity can be expressed in terms of the function f.Comment: 14 pages, 8 figure
Single spin asymmetry for in perturbative QCD
Within the QCD-improved parton model and assuming the factorization theorem
to hold in the helicity basis and for higher twist contributions, we show how
non zero single spin asymmetries in hadron-hadron high energy and moderately
large inclusive processes can be obtained, even in massless perturbative
QCD, provided the quark intrinsic motion is taken into account. A simple model
is constructed which reproduces the main features of the data on the single
spin asymmetry observed in inclusive pion production in collisions.Comment: 11 pages + 1 figure, plain LaTeX, figure appended as uuencoded,
compressed postscript file. Revised version, to be published in Phys. Lett.
B; extensive changes in Sections 1 and 2, new References added, results and
conclusions essentially unchange
Weighted azimuthal asymmetries in a diquark spectator model
We analytically calculate weighted azimuthal asymmetries in semi-inclusive
lepton-nucleon deep-inelastic scattering and Drell-Yan processes, using
transverse-momentum-dependent partonic densities obtained in a diquark
spectator model. We compare the asymmetries with available preliminary
experimental data, in particular for the Collins and the Sivers effect. We make
predictions for other cases of interest in running and planned experiments.Comment: 21 pages, 13 (multiple) figures in eps format, RevTeX
Azimuthal Spin Asymmetries of Pion Electroproduction
Azimuthal spin asymmetries, both for charged and neutral pion production in
semi-inclusive deep inelastic scattering of unpolarized charged lepton beams on
longitudinally and transversely polarized nucleon targets, are analyzed and
calculated. Various assumptions and approximations in the quark distributions
and fragmentation functions often used in these calculations are studied in
detail. It is found that different approaches to the distribution and
fragmentation functions may lead to quite different predictions on the
azimuthal asymmetries measured in the HERMES experiments, thus their effects
should be taken into account before using the available data as a measurement
of quark transversity distributions. It is also found that the unfavored quark
to pion fragmentation functions must be taken into account for
production from a proton target, although they can be neglected for and
production. Pion production from a proton target is suitable to study
the quark transversity distribution, whereas a combination of pion
production from both proton and neutron targets can measure the flavor
structure of quark transversity distributions.Comment: 31 latex pages, 13 figure, to appear in PR
Intrinsic transverse momentum and the polarized Drell-Yan process
In this paper we study the cross section at leading order in for
polarized Drell-Yan scattering at measured lepton-pair transverse momentum
. We find that for a hadron with spin the quark content at leading
order is described by six distribution functions for each flavor, which depend
on both the lightcone momentum fraction , and the quark transverse momentum
\bbox{k}_T^2. These functions are illustrated for a free-quark ensemble. The
cross sections for both longitudinal and transverse polarizations are expressed
in terms of convolution integrals over the distribution functions.Comment: 25 pages, REVTEX 3.0 (3 figures included in separate LATEX file using
feynman.tex), NIKHEF-94-P1 (Revised version
Double transverse spin asymmetries in vector boson production
We investigate a helicity non-flip double transverse spin asymmetry in vector
boson production in hadron-hadron scattering, which was first considered by
Ralston and Soper at the tree level. It does not involve transversity functions
and in principle also arises in W-boson production for which we present the
expressions. The asymmetry requires observing the transverse momentum of the
vector boson, but it is not suppressed by explicit inverse powers of a large
energy scale. However, as we will show, inclusion of Sudakov factors causes
suppression of the asymmetry, which increases with energy. Moreover, the
asymmetry is shown to be approximately proportional to x_1 g_1(x_1) x_2 \bar
g_1(x_2), which gives rise to additional suppression at small values of the
light cone momentum fractions. This implies that it is negligible for Z or W
production and is mainly of interest for \gamma^* at low energies. We also
compare the asymmetry with other types of double transverse spin asymmetries
and discuss how to disentangle them.Comment: 12 pages, Revtex, 2 Postscript figures, uses aps.sty, epsf.sty;
figures replaced, a few minor other correction
Mutations in SELENBP1, encoding a novel human methanethiol oxidase, cause extraoral halitosis
Selenium-binding protein 1 (SELENBP1) has been associated with several cancers, although its exact role is unknown. We show that SELENBP1 is a methanethiol oxidase (MTO), related to the MTO in methylotrophic bacteria, that converts methanethiol to H2O2, formaldehyde, and H2S, an activity not previously known to exist in humans. We identified mutations in SELENBP1 in five patients with cabbage-like breath odor. The malodor was attributable to high levels of methanethiol and dimethylsulfide, the main odorous compounds in their breath. Elevated urinary excretion of dimethylsulfoxide was associated with MTO deficiency. Patient fibroblasts had low SELENBP1 protein levels and were deficient in MTO enzymatic activity; these effects were reversed by lentivirus-mediated expression of wild-type SELENBP1. Selenbp1-knockout mice showed biochemical characteristics similar to those in humans. Our data reveal a potentially frequent inborn error of metabolism that results from MTO deficiency and leads to a malodor syndrome
Structure functions in the polarized Drell-Yan processes with spin-1/2 and spin-1 hadrons: II. parton model
We analyze the polarized Drell-Yan processes with spin-1/2 and spin-1 hadrons
in a parton model. Quark and antiquark correlation functions are expressed in
terms of possible combinations of Lorentz vectors and pseudovectors with the
constrains of Hermiticity, parity conservation, and time-reversal invariance.
Then, we find tensor polarized distributions for a spin-1 hadron. The naive
parton model predicts that there exist 19 structure functions. However, there
are only four or five non-vanishing structure functions, depending on whether
the cross section is integrated over the virtual-photon transverse momentum
\vec Q_T or the limit Q_T->0 is taken. One of the finite structure functions is
related to the tensor polarized distribution b_1, and it does not exist in the
proton-proton reactions. The vanishing structure functions should be associated
with higher-twist physics. The tensor distributions can be measured by the
quadrupole polarization measurements. The Drell-Yan process has an advantage
over the lepton reaction in the sense that the antiquark tensor polarization
could be extracted rather easily.Comment: 27 pages, REVTeX, amsmath.sty, epsfig.sty, revtex.cls, 2 eps figures.
Phys. Rev. D in press. Complete postscript file is available at
http://www2.cc.saga-u.ac.jp/saga-u/riko/physics/quantum1/structure.html
Email: [email protected], [email protected]
Mutations in SELENBP1, encoding a novel human methanethiol oxidase, cause extraoral halitosis
Selenium-binding protein 1 (SELENBP1) has been associated with several cancers, although its exact role is unknown. We show that SELENBP1 is a methanethiol oxidase (MTO), related to the MTO in methylotrophic bacteria, that converts methanethiol to H2O2, formaldehyde, and H2S, an activity not previously known to exist in humans. We identified mutations in SELENBP1 in five patients with cabbage-like breath odor. The malodor was attributable to high levels of methanethiol and dimethylsulfide, the main odorous compounds in their breath. Elevated urinary excretion of dimethylsulfoxide was associated with MTO deficiency. Patient fibroblasts had low SELENBP1 protein levels and were deficient in MTO enzymatic activity; these effects were reversed by lentivirus-mediated expression of wild-type SELENBP1. Selenbp1-knockout mice showed biochemical characteristics similar to those in humans. Our data reveal a potentially frequent inborn error of metabolism that results from MTO deficiency and leads to a malodor syndrome.info:eu-repo/semantics/publishedVersio
- …