Pseudoscalar Higgs boson production at hadron colliders in NNLO QCD

We compute the total cross-section for direct production of the pseudoscalar Higgs boson in hadron collisions at next-to-next-to-leading order (NNLO) in perturbative QCD. The O(alpha_s^2) QCD corrections increase the NLO production cross-section by approximately 20-30 per cent.Comment: 5 pages, revtex

NNLO Corrections to the Polarized Drell-Yan Coefficient Function

We present the full next-to-next-to-leading order (NNLO) corrections to the coefficient function for the polarized cross section $d \Delta\sigma/d Q$ of the Drell-Yan process. We study the effect of these corrections on the process $p+p\to l^+l^-+`X'$ at an C.M. energy $\sqrt{S}=200 GeV$. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for a lepton pair invariant mass $Q<50 GeV$. For this reaction the dominant subprocess is given by $q+\bar q\to \gamma^*+`X'$ and its higher order corrections so that it provides us with an excellent tool to measure the polarized sea-quark densities.Comment: 5 pages, 5 figures, 7th DESY Workshop on Elementary Particle Theory, Loops and Legs in Quantum Field Theory, Zinnowitz, Germany, April 25-30, 200

Bottom quark electroproduction in variable flavor number schemes

Two variable flavor number schemes are used to describe bottom quark production in deep inelastic electron-proton scattering. In these schemes the coefficient functions are derived from mass factorization of the heavy quark coefficient functions presented in a fixed flavor number scheme. Also one has to construct a parton density set with five light flavors (u,d,s,c,b) out of a set which only contains four light flavors (u,d,s,c). In order $\alpha_s^2$ the two sets are discontinuous at $\mu=m_b$ which follows from mass factorization of the heavy quark coefficient functions when it is carried out in the ${\bar {\rm MS}}$-scheme. Both variable flavor number schemes give almost identical predictions for the bottom structure functions $F_{2,b}$ and $F_{L,b}$. Also they both agree well with the corresponding results based on fixed order four-flavor perturbation theory over a wide range in $x$ and $Q^2$.Comment: Latex with seventeen PostScript figure

Molecular beam epitaxy of highly mismatched N-rich GaNSb and InNAs alloys

GaN materials alloyed with group V anions form the so-called highly mismatched alloys (HMAs). Recently, the authors succeeded in growing N-rich GaNAs and GaNBi alloys over a large composition range by plasma-assisted molecular beam epitaxy (PA-MBE). Here, they present first results on PA-MBE growth and properties of N-rich GaNSb and InNAs alloys and compare these with GaNAs and GaNBi alloys. The enhanced incorporation of As and Sb was achieved by growing the layers at extremely low growth temperatures. Although layers become amorphous for high As, Sb, and Bi content, optical absorption measurements show a progressive shift of the optical absorption edge to lower energy. The large band gap range and controllable conduction and valence band positions of these HMAs make them promising materials for efficient solar energy conversion devices

Top Quark Production Cross Section

The production rate for top quarks at the Fermilab Tevatron is presented using the exact order $\alpha_s^3$ corrected cross section and the resummation of the leading soft gluon corrections in all orders of perturbation theory.Comment: preprint FERMILAB-Pub-93/270-T, ITP-SB-93-55, THU-93/23, Latex 9 pages, 8 postscript figures, uuencoded and appended at end of fil

NLO corrections to differential cross sections for pseudo-scalar Higgs boson production

We have computed the full next-to-leading (NLO) QCD corrections to the differential distributions $d^2\sigma/(dp_T~dy)$ for pseudo-scalar Higgs (A) production at large hadron colliders. This calculation has been carried out using the effective Lagrangian approach which is valid as long as the mass of the pseudo-scalar Higgs boson $m_{\rm A}$ and its transverse momentum $p_T$ do not exceed the top-quark mass $m_t$. The shape of the distributions hardly differ from those obtained for scalar Higgs (H) production because, apart from the overall coupling constant and mass, there are only small differences between the partonic differential distributions for scalar and pseudo-scalar production. Therefore there are only differences in the magnitudes of the hadronic differential distributions which can be mainly attributed to the unknown mixing angle $\beta$ describing the pseudo-scalar Higgs coupling to the top quarks.Comment: 9 pages, LaTeX, 3 Postscript figures In the previous version we have forgotten to include contributions which arrise from interferences between graphs containing vertices corresponding to the operator $O_2(x)$ in Eq. (3) with graphs originating from the operator $O_1(x)$. These interferences occur because of the prescription for the Levi-Civita tensor given in our paper. These extra contributions are added to Eqs. (19) and (20). Numerically they are completely negligible so that the figures are not altere

The curvature of F2p(x,Q2)F_2^p(x,Q^2) as a probe of the range of validity of perturbative QCD evolutions in the small-xx region

Perturbative NLO and NNLO QCD evolutions of parton distributions are studied, in particular in the (very) small-$x$ region, where they are in very good agreement with all recent precision measurements of $F_2^p(x,Q^2)$. These predictions turn out to be also rather insensitive to the specific choice of the factorization scheme ($\bar{\rm MS}$ or DIS). A characteristic feature of perturbative QCD evolutions is a {\em{positive}} curvature of $F_2^p$ which increases as $x$ decreases. This perturbatively stable prediction provides a sensitive test of the range of validity of perturbative QCD.Comment: 17 pages, 6 figures, 2 tables; minor corrections, to appear in EPJ

NNLO corrections to massive lepton-pair production in longitudinally polarized proton-proton collisions

We present the full next-to-next-to-leading order (NNLO) coefficient functions for the polarized cross section $d\Delta \sigma/dQ$ for the Drell-Yan process $p + p\to l^+l^- + 'X'$. Here $'X'$ denotes any inclusive hadronic state and $Q$ represents the invariant mass of the lepton pair. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for $Q<50$ GeV. Unlike the differential distribution w.r.t. transverse momentum the dominant subprocess for the integrated cross section is given by $q+\bar q \to \gamma^* + 'X'$ and its higher order corrections so that massive lepton pair production provides us with an excellent tool to measure the polarized anti-quark densities. Our calculations are carried out using the method of $n$-dimensional regularization by making a special choice for the $\gamma_5$ matrix. We give predictions for double longitudinal spin asymmetry measurements at the RHIC.Comment: 45 pages, 22 figures. Due to a bug in our program the mass factorization plots in fig. 8-11 are changed. All parton density sets, in particular the set BB1 (J. Blumlein, H. Bottcher), lead to an improvement in the scale dependence while going from LO to NLO and then to NNL

Comparison between variable flavor number schemes for charm quark electroproduction

Where appropriate, the abbreviation 'VFNS' is replaced by 'CSN' to indicate the scheme using massive heavy quark coefficient functions proposed in this paper. The text below Eq. (2.13) and between Eqs. (2.33) and (2.36) has been considerably changed.Comment: 64 pages, LaTeX, 16 Postscript figure

Reconstructing the primordial power spectrum from the CMB

We propose a straightforward and model independent methodology for characterizing the sensitivity of CMB and other experiments to wiggles, irregularities, and features in the primordial power spectrum. Assuming that the primordial cosmological perturbations are adiabatic, we present a function space generalization of the usual Fisher matrix formalism, applied to a CMB experiment resembling Planck with and without ancillary data. This work is closely related to other work on recovering the inflationary potential and exploring specific models of non-minimal, or perhaps baroque, primordial power spectra. The approach adopted here, however, most directly expresses what the data is really telling us. We explore in detail the structure of the available information and quantify exactly what features can be reconstructed and at what statistical significance.Comment: 43 pages Revtex, 23 figure