Correlations in high transverse momentum final states

The author reviews experiments and results in the study of particle correlations in high energy collisions leading to high transverse momentum secondaries. Most of the effects observed in opposite direction with respect to that of a high p/sub perpendicular to / hadron, can be largely explained in terms of kinematic effects. These effects have made any search for jets of hadrons opposite to a high p /sub perpendicular to / hadron inconclusive-on the other hand, the positive momentum correlations observed between two high p/sub perpendicular to / hadrons in the same azimuthal region, are certainly of dynamical origin and must be studied further. (9 refs)

Accelerator and reactor neutrino experiments

Neutrino experiments at reactors and accelerators have provided a wealth of physics results and will continue to do so in the future. Over the next decade, these experiments will focus on oscillation studies. They will verify that the atmospheric neutrino results are indeed associated with oscillations and will provide more precise measurements of the oscillation parameters. They will also verify the large mixing angle MSW solution of the solar neutrino problem and provide information on the existence (or non-existence) of the fourth, sterile neutrino which is required if three independent Delta M/sup 2/ values are needed to explain all the observed oscillation signals. (34 refs)

The birth of lepton universality and the second neutrino

Bruno Pontecorvo has given many important contributions to particle physics, two of which were closely related to my work at the beginning of my career. I will discuss them here and I will also describe my first meeting with Bruno in 1973, on the occasion of a visit to Dubna

On the Optimum Long Baseline for the Next Generation Neutrino Oscillation Experiments

For high energy long baseline neutrino oscillation experiments, we propose a Figure of Merit criterion to compare the statistical quality of experiments at various oscillation distances under the condition of identical detectors and a given neutrino beam. We take into account all possible experimental errors under general consideration. In this way the Figure of Merit is closely related to the usual statistical criterion of number of sigmas. We use a realistic neutrino beam for an entry level neutrino factory and a possible superbeam from a meson source and a 100 kt detector for the calculation. We considered in detail four oscillation distances, 300 km, 700 km, 2100 km and 3000 km, in the neutrino energy range of 0.5-20 GeV for a 20 GeV entry level neutrino factory and a 50 GeV superbeam. We found that the very long baselines of 2100 km and 3000 km are preferred for the neutrino factory according to the figure of merit criterion. Our results also show that, for a neutrino factory, lower primary muon energies such as 20 GeV are preferred rather than higher ones such as 30 or 50 GeV. For the superbeam, the combination of a long baseline such as 300 km and a very long baseline like 2100 km will form a complete measurement of the oscillation parameters besides the CP phase. To measure the CP phase in a superbeam, a larger detector (a factor 3 beyond what is considered in this article) and/or a higher intensity beam will be needed to put some significant constraints on the size of the CP angle.Comment: 21 LaTeX pages, 13 PS figures, typos corrected, references adde

Search for solar Kaluza-Klein axions in theories of low-scale quantum gravity

We explore the physics potential of a terrestrial detector for observing axionic Kaluza-Klein excitations coming from the Sun within the context of higher-dimensional theories of low-scale quantum gravity. In these theories, the heavier Kaluza-Klein axions are relatively short-lived and may be detected by a coincidental triggering of their two-photon decay mode. Because of the expected high multiplicity of the solar axionic excitations, we find experimental sensitivity to a fundamental Peccei-Quinn axion mass up to $10^{-2}$ eV (corresponding to an effective axion-photon coupling $g_{a\gamma \gamma} \approx 2.\times 10^{-12}$ GeV$^{-1}$) in theories with 2 extra dimensions and a fundamental quantum-gravity scale $M_{\rm F}$ of order 100 TeV, and up to $3.\times 10^{-3}$ eV (corresponding to $g_{a\gamma \gamma} \approx 6.\times 10^{-13}$ GeV$^{-1}$) in theories with 3 extra dimensions and $M_{\rm F}=1$ TeV. For comparison, based on recent data obtained from lowest level underground experiments, we derive the experimental limits: $g_{a \gamma \gamma} \stackrel{<}{{}_\sim} 2.5\times 10^{-11}$ GeV$^{-1}$ and $g_{a \gamma \gamma} \stackrel{<}{{}_\sim} 1.2\times 10^{-11}$ GeV$^{-1}$ in the aforementioned theories with 2 and 3 large compact dimensions, respectively.Comment: 19 pages, extended version, as to appear in Physical Review

The CAST Time Projection Chamber

One of the three X-ray detectors of the CAST experiment searching for solar axions is a Time Projection Chamber (TPC) with a multi-wire proportional counter (MWPC) as a readout structure. Its design has been optimized to provide high sensitivity to the detection of the low intensity X-ray signal expected in the CAST experiment. A low hardware threshold of 0.8 keV is safely set during normal data taking periods, and the overall efficiency for the detection of photons coming from conversion of solar axions is 62 %. Shielding has been installed around the detector, lowering the background level to 4.10 x 10^-5 counts/cm^2/s/keV between 1 and 10 keV. During phase I of the CAST experiment the TPC has provided robust and stable operation, thus contributing with a competitive result to the overall CAST limit on axion-photon coupling and mass.Comment: 19 pages, 11 figures and images, submitted to New Journal of Physic

First results from the CERN Axion Solar Telescope (CAST)

Hypothetical axion-like particles with a two-photon interaction would be produced in the Sun by the Primakoff process. In a laboratory magnetic field (``axion helioscope'') they would be transformed into X-rays with energies of a few keV. Using a decommissioned LHC test magnet, CAST has been running for about 6 months during 2003. The first results from the analysis of these data are presented here. No signal above background was observed, implying an upper limit to the axion-photon coupling < 1.16 10^{-10} GeV^-1 at 95% CL for m_a <~0.02 eV. This limit is comparable to the limit from stellar energy-loss arguments and considerably more restrictive than any previous experiment in this axion mass range.Comment: 4 pages, accepted by PRL. Final version after the referees comment