Theoretical Production Cross Sections Research Articles

Transuranium isotopes at ISAC/TRIUMF

The production of transuranium isotopes has been demonstrated at the Isotope Separation and ACceleration (ISAC) facility. In particular a laser-ionized 239Pu beam, extracted from a uranium carbide target, was investigated. The experimental work was complemented by Geant4 simulations, modelling the impact of secondary particles on the creation of transuranium isotopes through inelastic nuclear reactions. Theoretical production cross sections were derived and compared to experimental results, leading to a discussion on boundary conditions for the release of neptunium and plutonium from ISAC uranium carbide targets.

Pair production of magnetic monopoles and stable high-electric-charge objects in proton–proton and heavy-ion collisions

We describe pair-production models of spin-0 and spin-½ magnetic monopoles and high-electric-charge objects (HECOs) in proton–proton (pp) and heavy-ion collisions, considering both the Drell–Yan (DY) and the photon-fusion processes. In particular, we extend the DY production model of spin-½ HECOs to include Z 0-boson exchange for pp collisions. Furthermore, we explore spin-½ and, for the first time, spin-0 production in ultraperipheral heavy-ion collisions. With matrix element calculations and equivalent photon fluxes implemented in MadGraph5_aMC@NLO, we present leading-order production cross sections of these mechanisms in TeV pp collisions and TeV ultraperipheral lead–lead collisions at the LHC. While the mass range accessible in ultraperipheral lead–lead collisions is much lower than that in pp collisions, we find that the theoretical production cross sections are significantly enhanced in the former for masses below 82 GeV.

Nuclear model analysis of the 65Cu(α, n)68Ga reaction for the production of 68Ga up to 40 MeV

The charge particle (α) induced reactions on enriched copper (65Cu) are investigated for the production of 68Ga. The data sets of experimental cross sections are compiled, normalized and nuclear model analysis is done using calculational codes namely, ALICE-IPPE, TALYS 1.95 and EMPIRE 3.2. The theoretical production cross sections via alpha particle induced reactions are calculated to present a set of recommended cross sections. The calculated cross sections are utilized to deduce thick target yield (TTY) for the 65Cu (α, n) 68Ga reaction. The range of energy for production of 68Ga is suggested up to 40 MeV having least contribution of radio-impurities.

Searches for direct pair production of supersymmetric top and supersymmetric bottom quarks inpp¯collisions ats=1.96 TeV

We search for direct pair production of supersymmetric top quarks and supersymmetric bottom quarks in proton-antiproton collisions at sqrt(s)=1.96 TeV, using 295 pb^-1 of data recorded by the Collider Detector at Fermilab (CDF II) experiment. The supersymmetric top (supersymmetric bottom) quarks are selected by reconstructing their decay into a charm (bottom) quark and a neutralino, which is assumed to be the lightest supersymmetric particle. The signature of such processes is two energetic heavy-flavor jets and missing transverse energy. The number of events that pass our selection for each search process is consistent with the expected standard model background. By comparing our results to the theoretical production cross sections of the supersymmetric top and supersymmetric bottom quarks in the minimal supersymmetric standard model, we exclude, at a 95% confidence level in the frame of that model, a supersymmetric top quark mass up to 132 GeV/c^2 for a neutralino mass of 48 GeV/c^2, and a supersymmetric bottom quark mass up to 193 GeV/c^2 for a neutralino mass of 40 GeV/c^2.

Zdecay into a bottom quark, a light sbottom, and a light gluino

The discrepancy between the measured and theoretical production cross section of $b$ quarks at the Tevatron can probably be explained by the recently proposed scenario of light gluinos of mass 12-16 GeV and light sbottoms of mass $2-5.5$ GeV. In this scenario, we study a related process at the $Z$ pole, $Z \to b \tilde{b}_1^* \tilde{g} + \bar b \tilde{b}_1 \tilde{g}$ followed by $\tilde{g} \to b \tilde{b}_1^* / \bar b \tilde{b}_1$. The hadronic branching ratio for this channel is $(1-3) \times 10^{-3}$, which is of order of the size of the uncertainty in $R_b$. We find that a typical event consists of an energetic prompt bottom-jet back-to-back with a ``fat'' bottom-jet, which consists of a bottom quark and two bottom squarks. Such events with a $10^{-3}$ branching ratio may affect the measurement of $R_b$; even more interesting if the ``fat'' bottom jet can be identified.

Production of vector-meson pairs in hadronic collisions

Production in hadronic collisions of 2/sup + +/ Q/sup 2/Q/sup 2/ states which decay predominantly to vector-meson pairs are discussed based on a Drell-Yan-type mechanism with gluon fusion via the color vector-dominance model. The 2/sup + +/ phiphi resonance at 2.16 GeV produced in pp and ..pi..p collisions is interpreted as a 2/sup + +/ sss-bar s-bar four-quark state. The calculated mass and width of this four-quark state, its characteristic S-wave decay, and the theoretical production cross sections in pp reaction at p/sub L/ = 400 GeV/c and ..pi..p reaction at p/sub L/ = 100 GeV/c are consistent with experimental data. Estimates of the hadronic production cross sections and their longitudinal- and transverse-momentum distributions for various channels of vector-meson pairs are also presented.

Unstable states produced in multiparticle reactions

Normalized wavefunctions for unstable-particle states are constructed to meet the following physically plausible specifications. The wavefunctions of such states should enter into the theoretical production cross section in the same manner as the boundstate wavefunctions of stable particles. The cross section for the production of an unstable particle should be equal to the breakup cross section integrated over the resonance minus the background. For this purpose the multiparticle reaction cross section is brought into a form such that final-state resonances and interference corrections can be exhibited explicitly. The present theory is limited to unstable particles that decay into one or several two-body channels. For heuristic purposes, rearrangement and breakup scattering for three simple particles is treated numerically. For two particles interacting via a local potential, the wavefunction of the unstable state and the scattering phase shifts are computed with a simple algebraic technique. In order to treat complex multiparticle systems, we extend the resonance theory of simple two-particle systems to resonances in multiparticle two-body channels.

Intermediate Boson. I. Theoretical Production Cross Sections in High-Energy Neutrino and Muon Experiments

We present here the theoretical total cross sections for $W$-boson production in the reactions $\ensuremath{\nu}+Z\ensuremath{\rightarrow}Z+W+\ensuremath{\mu}$ and $\ensuremath{\mu}+Z\ensuremath{\rightarrow}Z+W+\ensuremath{\nu}$ for a variety of $Z$. The emphasis is on the energies and corresponding $W$-boson masses pertinent to the National Accelerator Laboratory. The effects of the $W'\mathrm{s}$ anomalous magnetic moment, the nucleon Fermi motion, the Pauli exclusion principle, inelastic channels (in particular, deep-inelastic ones), and the problem of incoherent versus coherent production are all discussed. We also give a critique of some recent high-energy compilations.