Search results for "nuclear physics"
showing 10 items of 5307 documents
Measurement of the branching ratios of the decays Ξ0→Σ+e−ν¯e and Ξ0¯→Σ+¯e+νe
2007
Abstract From 56 days of data taking in 2002, the NA48/1 experiment observed 6316 Ξ 0 → Σ + e − ν ¯ e candidates (with the subsequent Σ + → p π 0 decay) and 555 Ξ 0 ¯ → Σ + ¯ e + ν e candidates with background contamination of 215 ± 44 and 136 ± 8 events, respectively. From these samples, the branching ratios BR ( Ξ 0 → Σ + e − ν ¯ e ) = ( 2.51 ± 0.03 stat ± 0.09 syst ) × 10 −4 and BR ( Ξ 0 ¯ → Σ + ¯ e + ν e ) = ( 2.55 ± 0.14 stat ± 0.10 syst ) × 10 −4 were measured allowing the determination of the CKM matrix element | V us | = 0.209 −0.028 +0.023 . Using the Particle Data Group average for | V us | obtained in semileptonic kaon decays, we measured the ratio g 1 / f 1 = 1.20 ± 0.05 of the …
Studying Chemical Properties of the Heaviest Elements: One Atom at a Time
2017
The search for heavier elements has been an exciting endeavor for nuclear scientists for many decades. This was invigorated after the first predictions that nuclear shell effects might render superheavy elements to have lifetimes long enough for their experimental study, or even their occurrence in Nature. A fascinating aspect concerns the question of their chemical properties: will they conform to the well-established structure of the Periodic Table of the Elements, or will so-called relativistic effects—a result of the high velocities of electrons in the vicinity of highly-charged nuclei—lead to dramatic deviations? Chemical studies of the heaviest elements are complicated by small produc…
γ-ray linear polarization measurements and(g9/2)−3neutron alignment in91Ru
2013
The authors would like to thank the operators of the GANIL cyclotrons for providing the 36Ar beam. We would also like to thank the EXOGAM Collaboration for use of the clover Ge detector array, the DIAMANT Collaboration for use of the charged particle detector system, and the European gamma-ray Spectroscopy Pool for use of the neutron detector system. We acknowledge funding support from the French-Polish LEA COPIGAL and the IN2P3-Polish laboratories COPIN Agreement No. 06-122, from the UK STFC, from the Swedish Research Council (Contracts No. 2007-4067 and No. 2008-5793), from the Goran Gustafsson Foundation, from the OTKA under Contract No. K100835, and from the Bolyai Janos Foundation. AG …
A direct measurement of |Vcs| in hadronic W decays using a charm tag
1999
Abstract The inclusive charm production rate in W decays is measured from a study of the properties of final state particles. The sample of W pairs is selected from 67.7 pb−1 collected by ALEPH in 1996 and 1997 at centre-of-mass energies near 172 and 183 GeV in the channels W+W−→4q and W + W − →lνq q . The branching fraction of hadronic W decays to a final state containing a c quark, RWc= Γ(W→cX)/Γ(W→hadrons), is measured to be 0.51±0.05stat±0.03syst. This allows a direct determination of the CKM matrix element |Vcs|=1.00±0.11stat±0.07syst.
ββ2νdecay in48Ca
2001
A schematic study of the $\ensuremath{\beta}\ensuremath{\beta}2\ensuremath{\nu}$ decay of ${}^{48}\mathrm{Ca}$ is made in a shell-model approach. The emphasis is especially put on the role of the spin-orbit potential in relation with the contribution of other terms in the strong interaction. This is discussed with a particular attention to the behavior of these ones under the SU(4) symmetry. Different methods in calculating the transition amplitude are also looked at with the aim to determine their reliability and, eventually, why they do not work. Further aspects relative to the failure of the operator expansion method to reproduce the results of more elaborate calculations are examined.
Study of the partial wave structure of π0η photoproduction on protons
2013
Abstract Analysis of the partial wave structure of γ p → π 0 η p reaction is presented in the energy region from threshold up to the total center-of-mass energy W = 1.9 GeV . Angular distributions measured with the Crystal Ball/TAPS hermetic detector system at the Mainz Microtron MAMI are expanded in terms of spherical harmonics. The relation of the extracted moments to the partial wave structure of the reaction amplitude is discussed and compared with predictions from model calculations.
E decays to ηππ in annihilation at rest
1995
Abstract We have observed the ηπ + π − and ηπ 0 π 0 decay modes of the E meson in p p annihilation at rest into π + π − π 0 π 0 η . The mass and width of the E meson are 1409 ± 3 and 86 ± 10 MeV. The production and decay branching ratio is B( p p → Eππ)B(E → ηππ) = (3.3 ± 1.0) × 10 −3 . With a spin-parity analysis we determine that J P = 0 − . The observation of the ηπ 0 π 0 decay mode establishes that E is isoscalar ( C = +1). We find that E decays to η ( ππ ) s (where ( ππ ) s is an S-wave dipion) and πa 0 (980)(→ πη ) with a relative branching ratio of (78 ± 16) %. Using the K K π production and decay branching ratio measured earlier we determine that B[E → K K π] B[E → ηππ] = 0.61 ± 0.1…
Observation of the decay KL→π0γγ
1990
Abstract The decay mode K L → π 0 γγ has been observed with a signal of 21 events and an expected background of 1.5±0.9 events. A branching ratio for decays with invariant γγ masses above 280 MeV of (2.1±0.6)×10 −6 is calculated. This result is compared with the values estimated from theoretical models and has implications for the CP conserving contribution to K L → π 0 e + e − decay.
Quantum numbers of theX(3872)state and orbital angular momentum in itsρ0J/ψdecay
2015
Angular correlations in B+→X(3872)K+ decays, with X(3872)→ρ0J/ψ, ρ0→π+π− and J/ψ→μ+μ−, are used to measure orbital angular momentum contributions and to determine the JPC value of the X(3872) meson. The data correspond to an integrated luminosity of 3.0 fb−1 of proton-proton collisions collected with the LHCb detector. This determination, for the first time performed without assuming a value for the orbital angular momentum, confirms the quantum numbers to be JPC=1++. The X(3872) is found to decay predominantly through S wave and an upper limit of 4% at 95% C.L. is set on the fraction of D wave.
Nuclear structure theory for the astrophysical rp-process and r-process
2003
Abstract The astrophysical processes of rapid-proton capture and rapid-neutron capture require the knowledge of many nuclear properties which are not known from experiment. I will describe two examples of how theoretical models are used to provide this input. The first of these uses the Hartree-Fock method for displacement energies to obtain the masses of proton-rich nuclei needed for the rp-process. The second uses a model for configuration mixing near 132 Sn to provide Q values and beta-decay lifetimes for the r-process.