The production of $\Upsilon$ mesons in $pp$ collisions at $\sqrt=7$ and $8\,\mathrm{TeV}$ is studied with the LHCb detector using data samples corresponding to an integrated luminosity of ...$1\,\mathrm{fb}^{-1}$ and $2\,\mathrm{fb}^{-1}$ respectively. The production cross-sections and ratios of cross-sections are measured as functions of the meson transverse momentum $p_T$ and rapidity $y$, for $p_T<30\,\mathrm{GeV}/c$} and $2.0<y<4.5$.
Using a dataset corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV, the $B_s^0 \to \phi \phi$ branching fraction is ...measured to be \ \mathcal{B}(B_s^0 \to \phi \phi) = ( 1.84 \pm 0.05 (\text{stat}) \pm 0.07 (\text{syst}) \pm 0.11 (f_s/f_d) \pm 0.12 (\text{norm}) ) \times 10^{-5}, \ where $f_s/f_d$ represents the ratio of the $B_s^0$ to $B^0$ production cross-sections, and the $B^0 \to \phi K^*(892)^0$ decay mode is used for normalization. This is the most precise measurement of this branching fraction to date, representing a factor five reduction in the statistical uncertainty compared with the previous best measurement. A search for the decay $B^0 \to \phi \phi$ is also made. No signal is observed, and an upper limit on the branching fraction is set as \ \mathcal{B}(B^0 \to \phi \phi) < 2.8 \times 10^{-8} \ at 90% confidence level. This is a factor of seven improvement compared to the previous best limit.
The neutron-rich nucleus Pt-200 is investigated via in-beam gamma-ray spectroscopy to study the shape evolution in the neutron-rich platinum isotopes towards the N = 126 shell closure. The ...two-neutron transfer reaction Pt-198(Se-82, Se-80)Pt-200 is used to populate excited states of Pt-200. The Advanced Gamma Ray Tracking Array (AGATA) demonstrator coupled with the PRISMA spectrometer detects gamma rays coincident with the Se-80 recoils, the binary partner of Pt-200. The binary partner method is applied to extract the gamma-ray transitions and build the level scheme of Pt-200. The level at 1884 keV reported by Yates et al. S. W. Yates, E. M. Baum, E. A. Henry, L. G. Mann, N. Roy, A. Aprahamian, R. A. Meyer, and R. Estep, Phys. Rev. C 37, 1889 (1988) was confirmed to be at 1882.1 keV and assigned as the (6(1)(+)) state. An additional gamma ray was found and it presumably deexcites the (8(1)(+)) state. The results are compared with state-of-the-art beyond mean-field calculations, performed for the even-even Pt190-204 isotopes, revealing that Pt-200 marks the transition from the gamma-unstable behavior of lighter Pt nuclei towards a more spherical one when approaching the N = 126 shell closure.
The lifetimes of the first excited states of the N=30 isotones Ca-50 and Sc-51 have been determined using the Recoil Distance Doppler Shift method in combination with the CLARA-PRISMA spectrometers. ...This is the first time such a method is applied to measure lifetimes of neutron-rich nuclei populated via a multinucleon transfer reaction. This extends the lifetime knowledge beyond the f(7/2) shell closure and allows us to derive the effective proton and neutron charges in the fp shell near the doubly magic nucleus Ca-48, using large-scale, shell-model calculations. These results indicate an orbital dependence of the core polarization along the fp shell.
The NA62 RICH detector is used for the separation of pions and muons in the momentum range 15-35 GeV/c and is expected to provide a muon suppression factor better than 10 -2 . A prototype of the ...final detector equipped with about 400 PMs (RICH-400 prototype) was built and tested in a dedicated run in 2009. The π-μ separation was tested, as well as the effect of the contamination of the neon radiator with different amounts of oxygen and CO 2 . The μ misidentification probability is about 0.7% and the time resolution better than 100 ps in the whole momentum range. We did not observe any absorption of the light due to the contamination of the radiator, however an effect on the ring radius is clearly observed due to the change of the refractive index of the medium. The conclusion of the studies is that the amount of CO 2 in the final detector should be known at the 10 -3 level of precision or the quality of the pion identification could be seriously compromised.
The CLARA-PRISMA setup installed at LNL: first results Gadea, A; Marginean, N; Corradi, L ...
Journal of Physics G: Nuclear and Particle Physics,
10/2005, Letnik:
31, Številka:
10
Journal Article, Conference Proceeding
Recenzirano
CLARA is an array of 25 Clover (EUROBALL type) Ge detectors, placed at the target position of the large acceptance magnetic spectrometer PRISMA. Due to the granularity of the CLARA Ge array (100 ...crystals), the photopeak efficiency ($\approx$3%) and the PRISMA large acceptance ($\approx$80 msr, and 20% $\Delta$p/p), the setup is an excellent tool to investigate the structure of neutron-rich nuclei, populated in multinucleon transfer reactions and deep inelastic collisions with stable beams. Since March 2004 the setup is fully operational, and since then several experiments have been performed, with beams delivered by the LNL XTU-Tandem and the ALPI linac. In this contribution the preliminary outcome of the first experiments is shown.
Excited states up to Iπ=8+ in the neutron-rich nucleus 58Cr have been identified by using a new experimental setup composed of the large acceptance magnetic spectrometer PRISMA and the highly ...efficient γ-detector array CLARA. Interestingly, the excitation energy sequence of the ground-state band follows the one expected by the E(5) dynamical symmetry for a nucleus at the critical point of the shape phase transition from a spherical vibrator (U(5)) to a γ-soft rotor (O(6)). For the first time, in the same physical system, large scale shell-model calculations in the full fp shell are compared to the E(5) analytical model results and to the Interacting Boson Model. The theoretical results are in excellent agreement with the present data.
From the 2002 data taking with a neutral kaon beam extracted from the CERN-SPS, the NA48/1 experiment observed 97 I 0 a IL + mu - I12 A= mu candidates with a background contamination of 30.8 +/- 4.2 ...events. From this sample, the BR (I 0 a IL + mu - I12 A= mu ) is measured to be (2.17 +/- 0.32 stat +/- 0.17 syst) X 10 - 6 .
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