Cross Section For Hadron Production Research Articles

Alternative analysis of theRmeasurements: Resonance parameters of the higher vector states of charmonium

The existing experimental data on total cross sections for hadron production in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation in the resonance region $\sqrt{s}=3.8\ensuremath{-}4.8\text{ }\text{ }\mathrm{GeV}$, usually presented in terms of the parameter $R$, are critically examined. It is shown that the Crystal Ball and BES measurements are in excellent agreement, and their analysis leads to consistent resonance parameters for the three vector resonances above the $D\overline{D}$ threshold. The results for the widths are found to be considerably different from the presently adopted values, and have much smaller errors.

Results from HARP

The HARP experiment at CERN is performing extensive measurements of hadron production cross sections and secondary particle yields in the energy range 1.5-15 GeV over the full solid angle, using a large set of cryogenic and solid targets. The hadron production in this region is a relevant ingredient in several branches of neutrino physics, including the characterization of neutrino beams, precise prediction of atmospheric neutrino fluxes, and quantification of pion production and capture for neutrino factory design. An overall precision of a few percent is required from the experiment to reach the final aim. The experimental layout comprises two spectrometers to perform momentum measurement of the secondaries produced in the target. The track momentum reconstruction in the spectrometers is complemented by a set of particle identification detectors that allow, with some redundancy, the particle type discrimination. Approximately 30 TB of data corresponding to 420 millions of events have been collected. The measurements of hadron production cross sections in the forward region (up to about 250 mrad) are reported using the K2K replica targets and a proton beam of 12.9 GeV/c. This is an appealing physics case given the immediate interest for those experiments and for the neutrino community.

HARP measurements of pion yield for neutrino experiment

The HARP experiment at CERN is performing extensive measurements of hadron production cross section and secondary particle yields in the momentum range of from 1.5 to 15 GeV/ c over full solid angle, using a large set of cryogenic and solid targets. This paper reports the first measurements of the momentum and angular distributions for pion production in the forward region using an 20mm thin aluminum target and a 12.9 GeV/ c proton beam, which are, respectively, the same target material and beam momentum as those used in K2K experiment.

Flux of light antimatter nuclei near Earth, induced by cosmic rays in the Galaxy and in the atmosphere

The fluxes of light antinuclei $A\ensuremath{\le}4$ induced near Earth by cosmic ray interactions with the interstellar matter in the Galaxy and with the Earth's atmosphere are calculated in a phenomenological framework. The hadronic production cross section for antinucleons is based on a recent parametrization of a wide set of accelerator data. The production of light nuclei is calculated using coalescence models. For the standard coalescence model, the coalescence radius is fitted to the available experimental data. The nonannihilating inelastic scattering process for the antideuterons is discussed and taken into account for the first time via a more realistic procedure than used so far for antiprotons.

The HARP experiment: first physics results

The HARP experiment at CERN is performing extensive measurements of hadron production cross sections and secondary particle yields, in the momentum range 1.5-15 GeV/c, over the full solid angle and using a large set of cryogenic and solid targets. First measurements of hadron production cross-sections in the forward region are reported using an aluminium target 5% of an interaction length thick and a proton beam of 12.9 GeV/c. A preliminary analysis in the large angle region of elastic scattering events produced with the cryogenic hydrogen target at 3 GeV/c beam momentum is also presented.

Measurements of hadron production cross sections and secondary particle yields in the energy range 2-15 GeV using neutrino beam targets

The HARP experiment at CERN is performing extensive measurements of hadron production cross sections and secondary particle yields in the energy range 2-15 GeV over the full solid angle, using a large set of cryogenic and solid targets. Hadron production in this kinematic region is a relevant ingredient in several branches of neutrino physics, such as characterisation of neutrino beams, precise prediction of atmospheric neutrino fluxes, and measurement of pion production and capture for neutrino factory design. An overall precision of a few percent is required from the experiment to reach the final aim. First measurements of hadron production cross sections in the forward region (up to about 300 mrad), using a replica of the K2K target and a proton beam of 12.9 GeV/c, are reported. This is an appealing physics case, given the immediate interest for these experiments and for the neutrino community.

Radiative return at $\Phi$ - and B-factories: FSR for muon pair production at next-to-leading order

Muon pair production through the radiative return is of importance for a measurement of the hadronic production cross section in two ways: it provides an independent calibration and it may give rise to an important background for a measurement of the pion form factor. With this motivation the Monte Carlo event generator PHOKHARA is extended to include next-to-leading order radiative corrections to the reaction $e^+e^-\to \mu^+\mu^-\gamma$. Furthermore, virtual ISR corrections to FSR from pions are introduced, which extends the applicability of the generator into a new kinematical regime. Finally, the effect of photon vacuum polarization is introduced into this new version of the generator.

The HARP time projection chamber

The HARP experiment, at the CERN Proton Synchrotron, measures hadron production cross sections of protons of well known momenta (2 – 15 GeV/c) impinging on various solid and liquid targets. Precise pion yield measurements, for neutrino factory studies and atmospheric neutrino experiments have been completed over almost the full solid angle. The HARP Time Projection Chamber which is part of the large angle spectrometer, provides tracking and particle identification of secondaries with transverse momenta down to 20 MeV/c and at angles comprised between 10° and 160°. Built in a record time of less than 1.5 years its small size called for innovative solutions in order to conserve the maximum active detection volume. A short description of the HARP Time Projection Chamber, which operated successfully from August 2001, will be given in the following document. Preliminary results regarding track reconstruction and momentum resolution are also given.

Hadronic cross-sections in two photon processes at a future linear collider

In this note we address the issue of measurability of the hadronic cross-sections at a future photon collider as well as for the two-photon processes at a future high energy linear $e^+e^-$ collider. We extend, to higher energy, our previous estimates of the accuracy with which the \gamgam\ cross-section needs to be measured, in order to distinguish between different theoretical models of energy dependence of the total cross-sections. We show that the necessary precision to discriminate among these models is indeed possible at future linear colliders in the Photon Collider option. Further we note that even in the $e^+e^-$ option a measurement of the hadron production cross-section via \gamgam processes, with an accuracy necessary to allow discrimination between different theoretical models, should be possible. We also comment briefly on the implications of these predictions for hadronic backgrounds at the future TeV energy $e^+e^-$ collider CLIC.

Charm production from photon–proton reactions in a hadronic model

The cross section for photoproduction of charmed hadrons from protons is studied using an effective Lagrangian that includes heavy charmed mesons and baryons. Both two-body final states involving Λ c and charmed meson as well as three-body final states involving nucleon and charm–anticharm meson pair are included. An overall form factor is introduced in each process to take into account finite hadron sizes without breaking the gauge invariance. Using coupling constants determined either empirically or via SU(4) relations, we adjust the cutoff parameter in the form factor to reproduce measured total charmed hadron production cross section from photon–proton reactions at center-of-mass energy of 6 GeV. The resulting relative contribution from two-body and three-body final states is consistent with experiments. The predicted cross section for photoproduction of charmed hadron from protons near threshold is seen to be appreciable. The result is further compared with predictions from leading-order perturbative QCD.

The physics potential of the electron-positron collider daφne

The physics to be pursued at the electron‐positron collider DANE in Frascati with the detectors DEAR, FINUDA and KLOE is addressed, with particular emphasis on the test of discrete symmetries in the neutral kaon system, measurements of cross sections of hadron production following electron‐positron annihilation and tests of chiral perturbation theory to be carried out with KLOE and DEAR.

Search for manifestations of new physics in fermion-pair production at LEP

The measurements of hadron and lepton-pair production cross sections and leptonic forward–backward asymmetries performed with the L3 detector at centre-of-mass energies between 130 GeV and 189 GeV are used to search for new physics phenomena such as: contact interactions, exchange of virtual leptoquarks, scalar quarks and scalar neutrinos, effects of TeV strings in models of quantum gravity with large extra dimensions and non-zero sizes of the fermions. No evidence for these phenomena is found and new limits on their parameters are set.

Determination of γ/Z interference in e +e − annihilation at LEP

An S-Matrix ansatz is used to determine the mass and width of the Z boson, as well as the contributions of γ/Z interference and Z boson exchange to fermion-pair production. For this purpose we use hadron and lepton-pair production cross sections and lepton forward-backward asymmetries that have been measured with the L3 detector at centre-of-mass energies between 87 GeV and 189 GeV.

Jet and hadron production in photon-photon collisions

Di-jet and inclusive charged hadron production cross-sections measured in γγ collisions by OPAL are compared to NLO pQCD calculations. Jet shapes measured in γγ scattering by OPAL, in deep-inelastic ep scattering by H1 and in γp scattering by ZEUS are shown to be consistent in similar kinematic ranges. New results from TOPAZ on prompt photon production in γγ interactions are presented.

Search for new physics phenomena in fermion-pair production at LEP

The measurements of hadron and lepton-pair production cross sections and lepton-pair forward–backward asymmetries performed with the L3 detector at centre-of-mass energies between 130 GeV and 172 GeV are used to search for new physics phenomena. New physics effects involving four fermion vertices – contact interactions – are looked for in all channels. For hadron production the exchange of virtual leptoquarks and scalar quarks is studied. No evidence for deviations from the Standard Model expectations is found. Lower limits on the scale Λ of contact interactions in the range 1.2–7.1 TeV are obtained at the 95% confidence level for various models. Upper limits on the coupling strengths of leptoquarks and scalar quarks are derived.

NLO production and decay of quarkonium

We present a calculation of next-to-leading order (NLO) QCD corrections to total hadronic production cross sections and to light-hadron-decay rates of heavy quarkonium states. Both colour-singlet and colour-octet contributions are included. We discuss in detail the use of covariant projectors in dimensional regularization, the structure of soft-gluon emission and the overall finiteness of radiative corrections. We compare our approach with the NLO version of the threshold expansion technique recently introduced by Braaten and Chen. Most of the results presented here are new. Others represent the first independent reevaluation of calculations already known in the literature. In this case a comparison with previous findings is reported.

Parton distributions and heavy quark production on nucleon and nuclear targets

Abstract The perturbative QCD evolution equation and the respective parton distributions in a proton are discussed, mainly in small x region. The different possibilities of shadow corrections are considered which allow one to avoid the unitarity violation. The possibility of estimation of the quality of phenomenological sets of the structure functions on the base of perturbative QCD is presented. Two approximate methods to extract the gluon distributions directly from the F2(x, Q2) data are discussed together with the new HERA data. Charm and beauty hadroproduction and photoproduction processes are considered in the framework of perturbative QCD and the results are compared with conventional parton model predictions. The role of infrared region contribution to F2(xQ2) structure function is discussed. The case of nuclear targets is considered also and A-dependences of charmed and beauty hadron production cross sections are calculated accounting for the difference of parton distributions in free and bound n...

On the infrared sensitivity of the longitudinal cross section in e +e − annihilation

We have calculated the contributions proportional to β0nαsn+1 to the longitudinal fragmentation function in e+e− annihilation to all orders of perturbation theory. We use this result to estimate higher-order perturbative corrections and nonperturbative corrections to the longitudinal cross section σL and discuss the prospects of determining αs from σL. The structure of infrared renormalons in the perturbative expansion suggests that the longitudinal cross section for hadron production with fixed momentum fraction x receives nonperturbative contributions of order 1/(x2Q2), whereas the total cross section has a larger, 1/Q correction. This correction arises from very large longitudinal distances and is related to the behaviour of the Borel integral for the cross section with fixed x at large values of the Borel parameter.

Hadronic production ofS- andP-wave states of $$\bar b$$ -quarkonium-quarkonium

In the leading $O(\alpha_s^4)$ order of the perturbative QCD, the hadronic production cross-sections of $S$- and $P$-wave states of $B_c$ meson are calculated. The results for the $S$-wave levels are compared with the values given in other papers as well as in the model of the $b$ quark fragmenatation into $B_c$. In the given order, the cross-sections of the hadronic production of the $P$-wave states are calculated for the first time. Their contribution into the $B_c$ meson production is less than 10\%. There is a strong difference between the predictions of the fragmentation model and the exact perturbative calculations. These difeerences are discussed in details for the differential distributions over various kinematical quantities.

Rhad at the B-factory

A systematic theoretical evaluation of the cross section for hadron production in electron-positron collisions in the energy range just below the B meson threshold is presented which includes charm and bottom mass effects and is accurate to order α s 3. The corresponding measurement in the energy region several GeV above the threshold is also discussed.