1,042 research outputs found
Analytic Solution for the Revised Helicity Evolution at Small and Large : New Resummed Gluon-Gluon Polarized Anomalous Dimension and Intercept
We construct an exact analytic solution of the revised small- helicity
evolution equations derived recently. The equations we solve are obtained in
the large- limit (with the number of quark colors) and are
double-logarithmic (summing powers of with the
strong coupling constant and the Bjorken variable). Our solution
provides small-, large- expressions for the flavor-singlet quark and
gluon helicity parton distribution functions (PDFs) and for the structure
function, with their leading small- asymptotics given by \begin{align}
\Delta \Sigma (x, Q^2) \sim \Delta G (x, Q^2)
\sim g_1 (x, Q^2) \sim \left( \frac{1}{x} \right)^{\alpha_h} , \notag
\end{align} where the exact analytic expression we obtain for the intercept
can be approximated by . Our solution also yields an all-order (in )
resummed small- anomalous dimension which
agrees with all the existing fixed-order calculations (to three loops).
Notably, our anomalous dimension is different from that obtained in the
infrared evolution equation framework developed earlier by Bartels, Ermolaev,
and Ryskin (BER), with the disagreement starting at four loops. Despite the
previously reported agreement at two decimal points based on the numerical
solution of the same equations, the intercept of our large- helicity
evolution and that of BER disagree beyond that precision, with the BER
intercept at large given by a different analytic expression from ours
with the numerical value of . We speculate on the origin of this disagreement.Comment: 22 pages, 3 figure
Tagging Two-Photon Production at the LHC
Tagging two-photon production offers a significant extension of the LHC
physics programme. Effective luminosity of high-energy gamma-gamma collisions
reaches 1% of the proton-proton luminosity and the standard detector techniques
used for measuring very forward proton scattering should allow for a reliable
extraction of interesting two-photon interactions. Particularly exciting is a
possibility of detecting two-photon exclusive Higgs boson production at the
LHC.Comment: 9 pages and 4 figure
A fast genetically encoded fluorescent sensor for faithful in vivo acetylcholine detection in mice, fish, worms and flies
Here we design and optimize a genetically encoded fluorescent indicator, iAChSnFR, for the ubiquitous neurotransmitter acetylcholine, based on a bacterial periplasmic binding protein. iAChSnFR shows large fluorescence changes, rapid rise and decay kinetics, and insensitivity to most cholinergic drugs. iAChSnFR revealed large transients in a variety of slice and in vivo preparations in mouse, fish, fly and worm. iAChSnFR will be useful for the study of acetylcholine in all organisms
The "quasi-stable" lipid shelled microbubble in response to consecutive ultrasound pulses
Controlled microbubble stability upon exposure to consecutive ultrasound exposures is important for increased sensitivity in contrast enhanced ultrasound diagnostics and manipulation for localised drug release. An ultra high-speed camera operating at 13 à 10 6 frames per second is used to show that a physical instability in the encapsulating lipid shell can be promoted by ultrasound, causing loss of shell material that depends on the characteristics of the microbubble motion. This leads to well characterized disruption, and microbubbles follow an irreversible trajectory through the resonance peak, causing the evolution of specific microbubble spectral signatures. © 2012 American Institute of Physics
A fast genetically encoded fluorescent sensor for faithful in vivo acetylcholine detection in mice, fish, worms and flies
Here we design and optimize a genetically encoded fluorescent indicator, iAChSnFR, for the ubiquitous neurotransmitter acetylcholine, based on a bacterial periplasmic binding protein. iAChSnFR shows large fluorescence changes, rapid rise and decay kinetics, and insensitivity to most cholinergic drugs. iAChSnFR revealed large transients in a variety of slice and in vivo preparations in mouse, fish, fly and worm. iAChSnFR will be useful for the study of acetylcholine in all organisms
Conceptual design of the MHD Engineering Test Facility
The reference conceptual design of the MHD engineering test facility, a prototype 200 MWe coal-fired electric generating plant designed to demonstrate the commerical feasibility of open cycle MHD is summarized. Main elements of the design are identified and explained, and the rationale behind them is reviewed. Major systems and plant facilities are listed and discussed. Construction cost and schedule estimates are included and the engineering issues that should be reexamined are identified
The Higgs - photon - Z boson coupling revisited
We analyze the coupling of CP-even and CP-odd Higgs bosons to a photon and a
Z boson in extensions of the Standard Model. In particular, we study in detail
the effect of charged Higgs bosons in two-Higgs doublet models, and the
contribution of SUSY particle loops in the minimal supersymmetric extension of
the Standard Model. The Higgs- coupling can be measured in the decay
+Higgs at colliders running on the Z resonance, or in
the reverse process Higgs with the Higgs boson produced at LHC.
We show that a measurement of this coupling with a precision at the percent
level, which could be the case at future colliders, would allow to
distinguish between the lightest SUSY and standard Higgs bosons in large areas
of the parameter space.Comment: 18 pages LaTex + 7 figures (ps). Typo corrected in eq.(5
TricycloÂ[3.3.1.03,7]nonane-3,7-diyl bisÂ(methaneÂsulfonate)
The crystal structure of the title compound, C11H18O6S2, was determined to investigate the effect of the eclipsed mesyl groups on the bond length of the vicinal quaternary C atoms. The two quaternary C atoms of the noradamantane skeleton and the two O atoms to which they are connected all located essentially in the same plane [maximum deviation 0.01â
Ă
], resulting in an eclipsing conformation of the CâO bonds. The CâC bond of the quaternary C atoms is 1.597â
(3)â
Ă
is considerably longer than the other CâC bonds of the molÂecule
R-parity violation and uses of the rare decay sneutrino-->gamma+gamma in hadron and photon colliders
We consider implications of the loop process sneutrino -> gamma gamma in the
MSSM with R-parity violation for future experiments, where the sneutrino is
produced as the only supersymmetric particle. We present a scenario for the
R-parity violating couplings, where this clean decay, although rare with
Br(sneutrino -> gamma gamma) ~ 10^{-6}, may be useful for sneutrino detection
over a range of sneutrino masses at the LHC. Furthermore, the new
sneutrino-gamma-gamma effective coupling may induce detectable sneutrino
resonant production in gamma gamma collisions, over a considerably wide mass
range. We compare sneutrino -> gamma gamma, gg throughout the paper with the
analogous yet quantitatively very different, Higgs -> gamma gamma, gg decays
and comment on the loop processes sneutrino -> WW, ZZ.Comment: 19 pages using REVTEX, 3 figures embadded in the text using epsfi
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