737 research outputs found
Ultrahigh energy neutrinos, small x and unitarity
The ultrahigh energy cross section for neutrino interactions with nucleons is
reviewed, and unitarity constraints are discussed. We argue that existing QCD
extrapolations are self-consistent, and do not imply a breakdown of the
perturbative expansion in the weak coupling.Comment: 5 pages, 2 figures, RevTeX4, contribution to Snowmass 200
Longitudinal spin transfer of Lambda and anti-Lambda in polarized pp collisions at \sqrt s=200 GeV at STAR
We report our measurement on longitudinal spin transfer, D_LL, from high
energy polarized protons to and hyperons in
proton-proton collisions at with the STAR detector at
RHIC. The current measurements cover , pseudorapidity
and transverse momenta up to using the data taken
in 2005. The longitudinal spin transfer is found to be D_LL= -0.03\pm 0.13
(stat) \pm 0.04(syst)\LambdaD_{LL} = -0.12 \pm
0.08(stat) \pm 0.03(syst)\bar{\Lambda} =
0.5 = 3.7 GeV/c$. The prospects with 2009 data and the future
measurements are also given.Comment: 6 pages, 3 figures, presentation at the SPIN2010 International
Symposium, Juelich (Germany), Sep. 27-Oct. 2, 201
Next-to-leading Order Evolution of Transversity Distributions and Soffer's Inequality
We present a calculation of the two-loop splitting functions for the
evolution of the twist-2 `transversity' parton densities of transversely
polarized nucleons. We study the implications of our results for Soffer's
inequality for the case of valence quark densities.Comment: 23 Pages, LaTeX, 2 figures as eps files, final, slightly modified
version, to appear in Phys. Rev.
A Simple Regulatory Incentive Mechanism Applied to Electricity Transmission Pricing and Investment
The Emerging QCD Frontier: The Electron Ion Collider
The self-interactions of gluons determine all the unique features of QCD and
lead to a dominant abundance of gluons inside matter already at moderate .
Despite their dominant role, the properties of gluons remain largely
unexplored. Tantalizing hints of saturated gluon densities have been found in
+p collisions at HERA, and in d+Au and Au+Au collisions at RHIC. Saturation
physics will have a profound influence on heavy-ion collisions at the LHC. But
unveiling the collective behavior of dense assemblies of gluons under
conditions where their self-interactions dominate will require an Electron-Ion
Collider (EIC): a new facility with capabilities well beyond those In this
paper I outline the compelling physics case for +A collisions at an EIC and
discuss briefly the status of machine design concepts. of any existing
accelerator.Comment: 11 pages, 9 figures, prepared for 20th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions: Quark Matter 2008 (QM2008),
Jaipur, India, 4-10 Feb. 200
Drell-Yan forward-backward and spin asymmetries for arbitrary vector boson production at next-to-leading order
Longitudinally polarized, unpolarized and forward-backward mass differential
cross sections for Drell-Yan lepton-pair production by arbitrary vector bosons
are calculated in next-to-leading order (NLO) QCD. Analytical results are
presented in a form valid for all consistent -dimensional regularization
schemes, with the mass factorization scheme kept general. NLO predictions for
all Drell-Yan type processes (, and ) at BNL's
relativistic heavy ion collider (RHIC) are made using polarized parton
distributions which fit the recent deep-inelastic scattering data. These are
examined as tools in the determination of the polarized parton distributions
and the unpolarized ratio. NLO predictions for the
forward-backward lepton asymmetry at Fermilab are made and the precision
determination of from future runs is studied. In all the
above, the QCD corrections are found to be significant. An introductory
discussion is given of various theoretical issues, such as allowable
factorization and regularization schemes, and scale dependences.Comment: 34 pages, figures included, revtex. Some discussions and references
added/modified. In more compact form. To appear in Phys. Rev.
On infimum Dickey–Fuller unit root tests allowing for a trend break under the null
Trend breaks appear to be prevalent in macroeconomic time series. Consequently, to avoid the catastrophic impact that unmodelled trend breaks have on power, it is standard empirical practice to employ unit root tests which allow for such effects. A popularly applied approach is the infimum ADF-type test. Its appeal has endured with practitioners despite results which show that the infimum ADF statistic diverges to −∞−∞ as the sample size diverges, with the consequence that the test has an asymptotic size of unity when a break in trend is present under the unit root null hypothesis. The result for additive outlier-type breaks in trend (but not intercept) is refined and shows that divergence to −∞−∞ occurs only when the true break fraction is smaller than 2/32/3. An alternative testing strategy based on the maximum of the original infimum statistic and the corresponding statistic constructed using the time-reversed sample data is considered
Relevance of baseline hard proton-proton spectra for high-energy nucleus-nucleus physics
We discuss three different cases of hard inclusive spectra in proton-proton
collisions: high single hadron production at 20 GeV and
at = 62.4 GeV, and direct photon production at = 200 GeV;
with regard to their relevance for the search of Quark Gluon Plasma signals in
A+A collisions at SPS and RHIC energies.Comment: Proceeds. Hot Quarks 2004 Int. Workshop on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions. 26 pages. 26 figs. [minor
corrs., refs. added
Robust tests for a linear trend with an application to equity indices
In this paper we develop a testing procedure for the presence of a deterministic linear trend in a univariate time series which is robust to whether the series is I(0) or I(1) and requires no knowledge of the form of weak dependence present in the data. Our approach is motivated by the testing procedures of Vogelsang [1998, Econometrica, vol 66, p123–148] and Bunzel and Vogelsang [2005, Journal of Business and Economic Statistics, vol 23, p381–394], but utilises an auxiliary unit root test to switch between critical values in the exact I(1) and I(0) environments, rather than using this unit root test to scale the test statistic as is done in the aforementioned procedures. We show that our proposed tests have uniformly greater local asymptotic power than the tests of Vogelsang (1998) and Bunzel and Vogelsang (2005) when the error process is exact I(1), identical local asymptotic when the error process is I(0), and have better overall local asymptotic power when the error process is near I(1). Our proposed tests also display superior finite sample power to the tests of Vogelsang (1998) and Bunzel and Vogelsang (2005) and are competitive in finite samples with tests designed to be optimal in both the exact I(1) and I(0) environments. We apply our test procedures to a number of equity indices and find that these series appear to have a significant upward deterministic trend, yet are also highly persistent about this long run growth path
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