Characteristics of multifragmentation of Au induced by 7 and 14.4 GeV He

The multifragmentation reaction channel has been investigated in the 7 and 14.4 GeV ⁴He interactions with Au target by using the CR-39 plastic track detector. Our experimental technique enabled an event-by-event analysis of the events. It has been observed that the multiplicity of events is not scaling with excitation energy. Also, an attempt has been made to reveal the scenario of multifragmentation by using angular correlations of fragments.     

Large angle hadron correlations from medium-induced gluon radiation

Final state medium-induced gluon radiation in ultradense nuclear matter is examined and shown to favor large angle emission when compared to vacuum bremsstrahlung due to the suppression of collinear gluons. Perturbative expression for the contribution of its hadronic fragments to the back-to-back particle correlations is derived. It is found that in the limit of large jet energy loss gluon radiation determines the yield and angular distribution of dihadrons to high transverse momenta p_T2 of the associated particles. Clear transition from enhancement to suppression of the away-side hadron correlations is established at moderate p_T2 and its experimentally accessible features are predicted versus the trigger particle momentum p_T1.     

Helium cosmic ray flux measurements at Mars

The helium energy spectrum in Martian orbit has been observed by the MARIE charged particle spectrometer aboard the 2001 Mars Odyssey spacecraft. The orbital data were taken from March 13, 2002 to October 28, 2003, at which time a very intense Solar Particle Event caused a loss of communication between the instrument and the spacecraft. The silicon detector stack in MARIE is optimized for the detection of protons and helium in the energy range below , which typically includes almost all of the flux during SPEs. This also makes MARIE an efficient detector for GCR helium in the energy range of 50–. We will present the first fully normalized flux results from MARIE, using helium ions in this energy range.     

Flux and energy distribution of axial protons emitted from the hydrogen plasma focus

Experimental results and theoretical studies show that protons from the hydrogen plasma focus are emitted predominantly in the axial direction. In this work the results of the flux and energy distribution measurements of the axial protons using CR-39 detector are presented. The main purpose of the experiment is to test the suitability of a plasma focus device as a source for (p,) nuclear reactions, especially and .     

Angular response of CR-39 to relativistic heavy ions and high-energy protons

Track etch detectors CR-39 irradiated with relativistic heavy ions (C, Ne, Si and Fe, ) and high-energy protons (35–230 MeV) were etched both chemically and electrochemically. To determine an angular dependence of response in detail (step 1), an arrangement of a single detector bent into a semi-cylindrical form was used. Experimental data were fitted by polynomic functions and the detection efficiencies for isotropic irradiation were calculated. Critical angles of registration were also determined for heavy ions. The possible influence of additional absorbers and radiators was also estimated.     

An irradiation chamber for experimental studies on SSNTD response to alpha particles

An irradiation apparatus was designed in our laboratory to study the detection efficiency dependence of SSNTDs (CR-39, LR115, Makrofol) on alpha particles of different energy and incident angle. The system was designed to irradiate up to nine detectors in a short time, allowing to obtain reproducible conditions on many detectors and therefore to reduce random variations of the results. The system is composed of a pressure-controlled stainless-steel chamber containing a ²⁴¹Am source and a circular rotating table with 10 detector holders, one of which is devoted to an ion-implanted silicon detector for irradiation energy monitoring. The table rotation is controlled electronically via a photodiode-based system, so that the position of the detectors under the source is known with a maximum uncertainty of 0.5 mm. The detector holders allow to change the detector (both passive and active) to source inclination angle continuously and with an uncertainty better than 1. The source-to-detector distance is controlled electronically and can be varied from 5 to 30 cm with an uncertainty of about 0.1 mm. Some simulations, obtained using the transport code TRIM, to project the irradiation chamber and its main characteristics are reported and discussed.     

Study of projectile fragmentation in the reaction (158 A GeV) Pb + Pb using CR-39

The fragmentation of Pb ions at 158 A GeV energy produced in the interaction with Pb target has been studied using a CR-39 track detector. A stack comprising of 64 detectors was prepared such that a target of 1 cm thickness was sandwiched between the sheets of CR-39. The purpose of this exposure geometry was to calibrate CR-39 with respect to relativistic heavy ions as well as to study the fragmentation of Pb ions at 158 A GeV energy. The exposure was carried out at the SPS beam facility of CERN at normal incidence with a fluence of . Two detectors from the exposed stack have been selected for this study: one before and the other after the target material. After etching, the detectors were scanned using an optical microscope and the etched track lengths and the diameters of the track openings were measured manually. Considering that the lengths of tracks provide the best charge resolution for Z>65, we have measured track lengths for a sufficiently large number of fragments to identify individual charge states for 65<Z<83. The total charge-changing cross section has also been determined.     

Chiral dynamics and antikaon-nuclear quasibound states

Recent developments are summarised concerning low-energy interactions as they relate to the possible existence of antikaon-nuclear quasibound states. An exploratory study of antikaons bound to finite nuclei is performed, with emphasis on the evolution of such states from light to heavy nuclei (A = 16–208). The energy dependent, driving attractive interactions are constructed using the s-wave coupled-channel amplitudes involving the Λ(1405) and resulting from chiral SU(3) dynamics, plus p-wave amplitudes dominated by the Σ(1385). Effects of Pauli and short-range correlations are discussed. The decay width induced by K⁻NN two-body absorption is estimated and found to be substantial. It is concluded that -nuclear quasibound states can possibly exist with binding energies ranging from 60 to 100 MeV, but with short life times corresponding to decay widths of similar magnitudes.     

Upgrading of LET track-etch spectrometer calibration: Calibration and uncertainty analysis

The spectrometer of linear energy transfer (LET) was developed several years ago. It is based on the chemically etched polyallyldiglycolcarbonate (PADC) track-etch detector. LET spectra are determined through track parameters determination and analysis by an automatic optical image analyser LUCIA G. For the past few years, we have used three materials, Page, 0.5 mm thick and Tastrak, 1 and 0.5 mm thick. To upgrade and determine their calibration curves, we have performed irradiation in high-energy heavier charged particle beams at Dubna, Russia and at Chiba, Japan. We were able to irradiate detectors by means of particles from ¹²C to ⁵⁶Fe with LET in water from 7.9 to . Upgraded calibration curves were obtained through a regression analysis, including systematic uncertainty estimation. The results obtained were combined with statistical uncertainty treatment and were used to analyse recently and previously obtained data. Examples of the results are presented and analysed.     

Development of a high speed imaging microscope and new software for nuclear track detector analysis

Automated digital imaging optical microscopy is widely used for diagnostic applications in the health care and biology fields and for routine inspection in industrial applications such as semiconductor fabrication. These applications require the imaging of large areas at high speed in order to obtain sufficient data for image processing with good statistics. Track detector analysis also benefits from the rapid acquisition of large areas on the detector surface. We have developed a new microscope system, the HSP-1000, for high speed image acquisition that uses a line sensor camera in place of a traditional CCD camera. Continuous, automatic focusing of the microscope is achieved by means of an optical pick-up system that provides fast feedback for control of distance between the objective and the image surface. Using transmitted light illumination, the microscope is able to digitize a area at resolution in . As a result of continuous stage motion and continuous focusing, we have attained image acquisition speeds that are 50–100 times faster than conventional CCD-based microscope systems. In this paper, we describe a number of aspects of the microscope system including the use of the line sensor and the automatic focus system.     

Measurement of neutron fluence with CR-39 using a UV spectrophotometer

Measurement of the correct neutron fluence in various energy intervals in and around the neutron sources is important for the purpose of personnel and environmental neutron dosimetry. In the present paper we present a method for the measurement of neutron fluence using a CR-39 plastic track detector. The samples exposed to fission neutrons from a reactor with 10¹²– fluence and to fast neutrons from a ²⁴¹Am–Be source with a fluence of were etched for 14 time intervals starting from 10 to 570 min in 6 N NaOH at . The etched samples were exposed to the monochromatic light signal from an iodine–tungsten lamp and the transmittance was measured after each etching time interval using a UV Spectrophotometer. An exponential decay of the transmittance has been observed with increasing etching time. The behaviour of the fission neutrons having four different values of fluence has been observed to be distinctly different from that of the fast neutrons. It has also been observed that there is a linear relationship between the transmittance decay constant and fission neutron fluence.     

production in exclusive B decays

Production of f₀(1710), a theoretical endeavor of pure scalar glueball state, is studied in detail from exclusive rare B decay within the framework of perturbative QCD. The branching fraction for is estimated to be about 8×10⁻⁶, while for it is smaller by roughly an order of magnitude. With the accumulation of almost 1 billion pairs from the BaBar and Belle experiments to date, hunting for a scalar glueball via these rare decay modes should be attainable.     

Spectral action and big desert

The values of the Higgs mass are obtained for two possibilities of extending the standard model in a way compatible with the existence of a noncommutative structure at high energies. We assume the existence of a big desert between the low energy electroweak scale and the high energy scale Λ=1.1×10¹⁷ GeV, where noncommutative features become relevant. We conclude that it is extremely difficult to depart from the Higgs mass value obtained from noncommutative geometry for the standard model with three generations only.     

Quadrupole collectivity of Ne and the boundary of the island of inversion

The excitation of the neutron-rich nucleus ²⁸Ne has been investigated via heavy-ion inelastic scattering in reversed kinematics. The value was determined to be , which is smaller than expected from the low excitation energy of the first state. A comparison with theoretical predictions suggests that the suppressed collectivity in ²⁸Ne is characteristic of nuclei lying on the boundary of the ‘island of inversion’.     

Comparison between theoretical model and experimental calibrations and its inference for track formation in bubble detectors

Calculations on the formation of a linear track of a heavy ion in bubble detector have been carried out based on a theoretical model considering the minimum energy (including bubble surface energy, internal energy, evaporation energy, expansion energy, kinetic energy and viscous energy) required during the formation of a critical bubble at the cost of the ionization energy of the heavy ion. The calculated minimum energy is 8.99 keV for dichlorodifluoromethane (R-12) at 25 °C. The results of calculations have been combined with those of calibrations of bubble detectors with heavy ions at accelerator. The threshold (1.51±0.04) MeV mg^-1 cm² is obtained in the calibration with heavy ions for the above liquid and temperature. It shows that the distance over which the heavy ion traverses and transfers energy to the superheated liquid to produce a critical bubble is 4.67 times the radius of the seed bubble. The radius of the cylinder along which the heavy ion deposits energy to form a seed bubble is about 5.2 nm. This dimension indicates that the process of track formation in bubble detectors is consistent with the model of thermal spike.     

: Hadronic molecules in effective field theory

We consider the implications from the possibility that the recently observed state X(3872) is a meson–antimeson molecule. We write an effective Lagrangian consistent with the heavy-quark and chiral symmetries needed to describe X(3872). We explore the consequences of the assumption that X(3872) is a molecular bound state of D^*0 and mesons for the existence of bound states in the and channels.     

Studies of UV-cured CR-39 recording properties in view of its applicability in radiobiological experiments with alpha particles

In radiobiology, low doses of high-LET radiation correspond to a few particle traversals through the cell population. Therefore, for studies on cell monolayers irradiated with a low dose of -particles, it is extremely useful if the number and position of particle traversals can be determined. In this study we describe a new method, based on UV-curing, to obtain a thick CR-39 grafted onto a thick PolyEthylene Terephtalate (PET). This thin double polymeric layer, used as a dish base, has a regular and reproducible detector thickness which can be traversed by 3.5 MeV -particles, with a sufficient residual energy to traverse mammalian cells attached to the base. The recording properties of a PET-CR-39 dish, together with a demonstration of its use for radiobiological experiments, are presented. This new tool allows the precise determination of single-track impact parameters at a sub-cellular level.     

A texture for neutrino oscillations and leptogenesis

In an economical system with only two heavy right-handed neutrinos, we postulate a new texture for 3×2 Dirac mass matrix m_D. This model implies one massless light neutrino and thus displays only two patterns of mass spectrum for light neutrinos, namely hierarchical or inverse-hierarchical. Both the cases can correctly reproduce all the current neutrino oscillation data with a unique prediction and for the hierarchical and the inverse-hierarchical cases, respectively, which can be tested in next generation neutrino-less double beta decay experiments. Introducing a single physical CP phase in m_D, we examine baryon asymmetry through leptogenesis. Interestingly, through the CP phase there are correlations between the amount of baryon asymmetry and neutrino oscillation parameters. We find that for a fixed CP phase, the hierarchical case also succeeds in generating the observed baryon asymmetry in our universe, plus a non-vanishing U_e3 which is accessible in future baseline neutrino oscillation experiments.     

A study of strange particles produced in neutrino neutral current interactions in the NOMAD experiment

Results of a detailed study of strange particle production in neutrino neutral current interactions are presented using the data from the NOMAD experiment. Integral yields of neutral strange particles (, Λ, ) have been measured. Decays of resonances and heavy hyperons with an identified or Λ in the final state have been analyzed. Clear signals corresponding to and Σ(1385)^± have been observed. First results on the measurements of the Λ polarization in neutral current interactions have been obtained.