Fine-structure splittings of excited P-and D-wave states in charmonium

It is shown that, in the relativistic case, the fine-structure splittings of the excited 2³ P _J and 3³ P _J states in charmonium are as large as those of the 1³ P _J state if the same value of α_s(μ)≈0.36 is used. The predicted mass of M(2³ P ₀)=3.84 GeV appears to be 120 MeV lower than the center of gravity of the 2³ P _J multiplet and lies below the D $\bar D$ ^* threshold. Our value of M(2³ P ₀) is nearly 80 MeV lower than that from the Godfrey and Isgur article [Phys. Rev. D 32, 189 (1985)], while the differences in other masses are not greater than 20 MeV.     

An alternative for polarized antiproton beams

Presently the most popular way to prepare high quality polarized antiproton beams is the so called spin filter method. The feasibility of the method has been proven for a proton beam and measurements of the spin dependent interaction of antiprotons have been proposed by the PAX collaboration. Another well known source for polarized antiprotons is the $\bar{\Lambda}$ decay which was used at FERMILAB in the only experiment performed so far with polarized antiprotons. An alternative approach for polarized antiproton beams may be the production process itself. If the produced antiprotons show polarization it would be rather simple to handle a polarized antiproton beam in the existing antiproton collector and cooler at CERN just like in the unpolarized case.     

A search for mechanoluminophors capable of pressure-induced thermal population of excited states

During the process of deforming a crystal, a high pressure is developed near the tip of mobile cracks, which may in turn produce a new ground state by thermal electron transfer. Upon sudden release of pressure, the electron can either relax to one atmosphere ground state or remain in the excited state potential well long enough to relax to one atmosphere and radiatively transfer back to the ground state. For analysing the pressure induced thermal population of the excited state, the mechanoluminescence(ML) and high pressure photoluminescence(PL) of several organic and inorganic crystals were measured. The study indicated that usual pressure coefficient of energy shift of the order of 50–100 cm⁻¹/kbar and the stress at the crack-tip of the order of 5–10 kbar, are not sufficient to cause the thermal population of the excited state. If by any means the product of pressure coefficient and stress at the mobile crack-tip can be increased by 50 to 100 times, then the thermal population of the excited states may take place. Using the pressure coefficient of energy shift and the difference in ML and PL spectra, and using independently the change in relative intensities of the vibronic peaks, the pressure at the emitting mechanoluminescent crystal sites is evaluated and it is found to be of the order of several kbar which varies from crystal to crystal.     

Antihydrogen formation in low-energy antiproton collisions with excited-state positronium atoms

The convergent close-coupling method is used to obtain cross sections for antihydrogen formation in low-energy antiproton collisions with positronium (Ps) atoms in specified initial excited states with principal quantum numbers n_i ≤?5. The threshold behaviour as a function of the Ps kinetic energy, E, is consistent with the 1/E law expected from threshold theory for all initial states. We find that the increase in the cross sections is muted above n_i =?3 and that here their scaling is roughly consistent with \({n_{i}^{2}}\), rather than the classically expected increase as \({n_{i}^{4}}\).     

The glueball G(1440) and radially excited pseudoscalar states

It is pointed out that there exist two isoscalar 0^?+ states near 1.4 GeV besides the axial-vector E(1420), one is a glueball and the other is a member of the radially excited pseudoscalar nonet. The relationship between the (2 ¹S₀)- and (1 ³P₁)- trajectories is discussed.     

Prospects for antiproton experiments at Fermilab

Fermilab operates the world’s most intense antiproton source. Newly proposed experiments can use those antiprotons either parasitically during Tevatron Collider running or after the end of the Tevatron Collider program. For example, the annihilation of 5 to 8 GeV antiprotons is expected to yield world-leading sensitivities to hyperon rare decays and CP violation. It could also provide the world’s most intense source of tagged D ⁰ mesons, and thus the best near-term opportunity to study charm mixing and, via CP violation, to search for new physics. Other measurements that could be made include properties of the X(3872) and the charmonium system. An experiment using a Penning trap and an atom interferometer could make the world’s most precise measurement of the gravitational force on antimatter. These and other potential measurements using antiprotons offer a great opportunity for a broad and exciting physics program at Fermilab in the post-Tevatron era.     

Radial compression of an antiproton cloud for production of intense antiproton beams

We report here the radial compression of a large number of antiprotons ( approximately 5 x 10(5)) in a strong magnetic field under ultrahigh vacuum conditions by applying a rotating electric field. Compression without any resonant structures was demonstrated for a range of frequencies from the sideband frequency of 200 kHz to more than 1000 kHz. The radial compression achieved is a key technique for synthesizing and manipulating antihydrogen atoms and antiprotonic atoms.     

FLAIR – a facility for low-energy antiproton and ion research

In order to exploit the unique possibilities that will become available at the Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, a collaboration of about 50 institutes from 15 countries was formed to efficiently enable an innovative research program towards low-energy antimatter-physics. In the Facility for Low-energy Antiproton and Ion Research (FLAIR) antiprotons and heavy (radioactive) ions are slowed down from 30 MeV to energies as low as 20 keV by a magnetic low-energy storage ring (LSR) and an electrostatic ultra-low energy storage ring (USR) or are even brought to rest by a universal trap facility (HITRAP). In this paper, the facility and the research program covered are briefly described with some emphasis on the accelerator chain and the expected particle numbers. for the FLAIR collaboration     

A search for excited fermions at HERA

A search for excited fermions f of the first generation in scattering at the collider HERA is presented using H1 data with an integrated luminosity of 37 pb. All electroweak decays of excited fermions, f f f W,f Z are considered and all possible final states resulting from the Z orW hadronic decays or decays into leptons of the first two generations are taken into account. No evidence for f production is found. Mass dependent exclusion limits on cross-sections and on the ratio of coupling constants to the compositeness scale are derived. Received: 19 July 2000 / Published online: 23 October 2000     

A model search for Efimov states

A search for Efimov states is carried out in terms of a one-dimensional model three-body problem. A numerically exact solution is obtained that allows scanning through the resonance condition. No evidence is found for the existence of an infinite number of such bound three-body states. It is deduced from one-dimensional results that such an infinity of bound states should also not arise in a complete three-dimensional calculation.     

Forces in optical tweezers with radially and azimuthally polarized trapping beams

It has been suggested that radially polarized beams can be used to improve the performance of optical tweezers, with reduced scattering force resulting from both the polarization and the dark center of the beam [Opt. Lett. 32, 1839 (2007)]. We calculate the forces on particles in such traps, using rigorous electromagnetic theory, comparing the results with azimuthally polarized beam, circularly polarized LG 01 beams, and Gaussian beams. Our results agree qualitatively with Opt. Lett. 32, 1839 (2007), but differ quantitatively.     

A search for excited fermions in electron-proton collisions at HERA

A search for excited states of the standard model fermions was performed using the ZEUS detector at the HERA electron-proton collider, operating at a centre of mass energy of 296 GeV. In a sample corresponding to an integrated luminosity of 0.55 pb^–1, no evidence was found for any resonant state decaying into final states composed of a fermion and a gauge boson. Limits on the coupling strength times branching ratio of excited fermions are presented for masses between 50 GeV and 250 GeV, extending previous search regions significantly.supported by Worldlab Lausanne, Switzerland     

Fission experiments with secondary beams

Nuclear fission from excitation energies around 11 MeV was studied at GSI, Darmstadt for 76 neutron-deficient actinides and pre-actinides by use of relativistic secondary beams. The characteristics of multimodal fission of nuclei around ²²⁶Th are systematically investigated and related to the influence of shell effects on the potential-energy and on the level density between saddle point and scission. A systematic view on the large number of elemental yields measured gave rise to a new interpretation of the enhanced production of even elements in nuclear fission and allowed for a new understanding of pair breaking in fission.     

SCF theory for excited states

Equations of Hartree-Fock type are formulated for a many-electron system described by a wave function containing any number of open and closed shells. The solutions define ‘optimal orbitals’ which minimize the average energy of the states of a configuration in which each shell contains a specified number of electrons. Analogues of the Koopmans theorem are constructed.

The results obtained are of special interest in discussing highly excited states (e.g. in ESCA and Auger spectroscopy) where ‘holes’ may be present in both inner and outer shells.     

A formula for charmonium suppression

In this work a formula for charmonium suppression obtained by Matsui in 1989 is analytically generalized for the case of complex $c\bar c$ potential described by a 3-dimensional and isotropic time-dependent harmonic oscillator (THO). It is suggested that under certain scheme the formula can be applied to describe J/?? suppression in heavy-ion collisions at CERN-SPS, RHIC, and LHC with the advantage of analytical tractability.     

A high-efficient method for generating radially and azimuthally polarized Bessel beams using biaxial crystals

As was shown previously, in propagation of a circularly polarized Bessel light beam along the optical axes of a biaxial crystal, there takes place the conversion of the order of Bessel function. In this paper, a new result is presented which is obtained by varying the polarization state of an input beam. Namely, a linearly polarized beam can be transformed into a beam with the radial or azimuthal polarization state. At that the order-transformation also occurs. The switching between radial and azimuthal polarization states of the output beam is performed by the proper switching between two orthogonal linear polarization states of the input beam. The efficiency of polarization conversion is high and can be practically full at an appropriate choice of the cone angle of the input beam or crystal length.     

Evidence for excited states in 95Ag

The first evidence for excited states in ⁹⁵Ag is presented. ⁹⁵Ag is the heaviest T _z = 1/2 nucleus for which gamma-rays have been identified. The reaction ⁴⁰Ca(⁵⁸Ni, 1p2n)⁹⁵Ag was used in the experiment, which resulted in the assignment of three gamma-rays to ⁹⁵Ag. A detector system consisting of the detector arrays Euroball, Neutron Wall and Euclides was used to detect gamma-rays, neutrons and charged particles, respectively. Received: 31 May 2002 / Accepted: 8 July 2002     

Levelcrossing experiments in the first excited1 P 1 states of the alkaline earths

The hyperfine structure of the lowest¹P₁ state of²⁵Mg,⁴³Ca,⁸⁷Sr,¹³⁵Ba and¹³⁷Ba have been measured by the level-crossing and anticrossing technique. The magnetic dipole and electric quadrupole coupling constants determined by these measurements are²⁵Mg(3s3p¹P₁):A=? 7.7(5) MHz; 16 MHz>B>0 MHz,⁴³Ca(4s4p¹P₁):A=? 15.3(4) MHz; ¦B¦<12 MHz,⁸⁷Sr (5s5p¹P₁:A=? 3.4(4) MHz;B=39(4) MHz,¹³⁵Ba(6s6p¹P₁):A=? 97.5(1.0) MHz;B=31(9)MHz,¹³⁷Ba(6s6p¹P₁):A=?109.2(1.2) MHz;B=51(12)MHz. The results have been compared with the predictions of the Breit-Wills theory of the two-electron hyperfine structure using the experimental data on the³P states. Large discrepancies have been observed which are due to different radial wave functions of thes andp electron in the triplet and singlet system. This effect has been taken into account by fitting the data with the aid of two additional parameters. That this procedure is justified is shown by an analysis of the fine structure splitting, the life times, and the isotopic shifts in thesp configurations of group II elements.