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The beta-strength in beta-delayed particle decays has up to now been defined in a somewhat ad hoc manner that depends on the decay mechanism. A simple, consistent definition is presented that fulfils the beta strength sum rules. Special consideration is given to the modifications needed when employing R-matrix fits to data. As an example the 11Be(beta-p) decay is investigated through simple models.
We report on studies of untriggered two-particle angular correlations of identified particles (pions, kaons and protons) measured in proton-proton collisions at center-of-mass energy sqrt{s}=7 TeV recorded by ALICE at the LHC. These type of studies are sensitive to a wide range of correlations which arise from different physics mechanisms, each of them having a unique structure in DeltaEta-DeltaPhi space. The correlations of particles with different quark content and flavor are sensitive to various conservation laws. The study of these correlations is the main goal of this analysis. The results confirm that these laws strongly influence the shape of the correlation functions for different particle types and must be taken into account while analysing the data. Moreover, we verify their implementation using two Monte Carlo event generators and we found that the analyzed models do not reproduce the measured correlations for protons.
The electric dipole moments of the nucleon and light ions are discussed and strategies for disentangling the underlying sources of CP violation beyond the Kobayashi-Maskawa quark-mixing mechanism of the Standard Model are indicated. Contribution to "45 years of nuclear theory at Stony Brook: a tribute to Gerald E. Brown".
For a long time Gerry Brown and his collaborator Hans Bethe considered the question of the final fate of a core collapse (Type II) supernova. Recalling ideas from nuclear structure on Kaon condensate and a soft equation of state of the dense nuclear matter they concluded that progenitor stars with mass as low a 17-18M$_\odot$ (including supernova 1987A) could collapse to a small mass black hole with a mass just beyond 1.5M$_\odot$, the upper bound they derive for a neutron star. We discuss another nuclear structure effect that determines the carbon to oxygen ratio (C/O) at the end of helium burning. This ratio also determines the fate of a Type II supernova with a carbon rich progenitor star producing a neutron star and oxygen rich collapsing to a black hole. While the C/O ratio is one of the most important nuclear input to stellar evolution it is still not known with sufficient accuracy. We discuss future efforts to measure with gamma-beam and TPC detector the 12C(a,g)16O reaction that determines the C/O ratio in stellar helium burning.
We extract chemical freeze-out conditions via a thermal model approach from fluctuation observables measured at RHIC and compare with results from lattice QCD and statistical hadronization model fits. The possible influence of additional critical and non-critical fluctuation sources not accounted for in our analysis is discussed.
Search for double $β$ decay of $^{136}$Ce and $^{138}$Ce was realized with 732 g of deeply purified cerium oxide sample measured over 1900 h with the help of an ultra-low background HPGe $γ$ detector with a volume of 465 cm$^3$ at the STELLA facility of the Gran Sasso National Laboratories of the INFN (Italy). New improved half-life limits on double beta processes in the cerium isotopes were set at the level of $\lim T_{1/2}\sim 10^{17}-10^{18}$~yr; many of them are even two orders of magnitude larger than the best previous results.
Heavy quarks, i.e. charm and beauty, are considered calibrated probes for the strongly interacting deconfined medium (Quark Gluon Plasma, QGP) formed in heavy-ion collisions. Produced in hard scattering processes in the initial stages of the collision, they interact with the medium, lose energy and, depending on the coupling strength to the medium, take part in the collective motion of the QCD matter. ALICE measured the production of ${\rm D^{0}}$, ${\rm D^{*+}}$, ${\rm D^{+}}$ and ${\rm D_{s}}$ mesons at central rapidity in pp, p-Pb and Pb-Pb collisions at the LHC. The study of the modification of the transverse momentum differential yields of charm particles in Pb-Pb collisions with respect to pp collisions, quantified by the nuclear modification factor ($R_{\rm AA}$), can unravel details of the energy loss mechanism, such as its dependence on the quark mass and on the path length the parton travels through the medium. A similar comparison between pp and p-Pb collision data ($R_{\rm pPb}$) is fundamental to disentangle effects related to the presence of the hot medium from cold nuclear matter effects. The degree of thermalization and coupling to the medium is investigated in semi-peripheral Pb-Pb collisions by measuring the elliptic flow coefficient ($v_{2}$) at low pt. At high pt, $v_{2}$ is sensitive to the path-length dependence of the energy loss. Results on the transverse momentum and centrality dependence of the D-meson elliptic flow and $R_{AA}$ will be presented. The comparison with the $R_{\rm AA}$ of non-prompt ${\rm J/}ψ$ from B-meson decays measured with CMS will be discussed. The preliminary results on D-meson $R_{\rm pPb}$ and the dependence of D-meson yields on rapidity in p-Pb collisions will be shown. As an outlook, the analysis and the preliminary results on the azimuthal correlations of D mesons and charged hadrons in pp collisions will be described.
We study the collective flow of the {QGP}-fluid which transports the energy and momentum deposited from jets. Simulations of the propagation of jets together with expansion of the {QGP}-fluid are performed by solving relativistic hydrodynamic equations numerically in the fully (3+1)-dimensional space. Mach cones are induced by the energy-momentum deposition from jets and extended by the expansion of the {QGP}. As a result, a large fraction of the transverse momentum deposited from jets is compensated by low-$p_{T}$ particles at large angles from the jet axis. This result is consistent with the data from the {CMS} Collaboration and gives a novel interpretation of them.
Experimental and theoretical studies of fluctuations in nucleus-nucleus interactions at high energies have started to play a major role in understanding of the concept of strong interactions. The elaborated procedures have been developed to disentangle different processes happening during nucleus-nucleus collisions. The fluctuations caused by a variation of the number of nucleons which participated in a collision are frequently considered the unwanted one. The methods to eliminate these fluctuations in fixed-target experiments are reviewed and tested. They can be of key importance in the following ongoing fixed-target heavy-ion experiments: NA61/SHINE at the CERN SPS, STAR-FT at the BNL RHIC, BM\@N at JINR Nuclotron, HADES at the GSI SIS18 and in future experiments such as NA60+ at the CERN SPS, CBM at the FAIR SIS100, JHITS at J-PARC-HI MR.
In the context of multi-brane Universe models, matter swapping between two braneworlds is allowed leading to a baryon number violation in our visible world. An experimental framework is described to test such a phenomenology with cold neutrons thanks to a neutron-shining-through-a-wall experiment.
The polarization observable I^s, a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction g p -> p pi0 eta are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I^c. The comparably large asymmetries demonstrate a high sensitivity of I^s to the dynamics of the reaction. Fits using Bonn-Gatchina partial wave analysis demonstrate that the new polarization observables carry significant information on the contributing partial waves.
We report $J/ψ$ spectra for transverse momenta $p_T$> 5 GeV/$c$ at mid-rapidity in p+p and Au+Au collisions at sqrt(s_{NN}) = 200 GeV.The inclusive $J/ψ$ spectrum and the extracted $B$-hadron feed-down are compared to models incorporating different production mechanisms. We observe significant suppression of the $J/ψ$ yields for $p_T$> 5 GeV/$c$ in 0-30% Au+Au collisions relative to the p+p yield scaled by the number of binary nucleon-nucleon collisions in Au+Au collisions. In 30-60% collisions, no such suppression is observed.The level of suppression is consistently less than that of high-$p_T$ $π^{\pm}$ and low-$p_T$ $J/ψ$.
The ALICE collaboration at the CERN Large Hadron Collider reports the first measurement of the inclusive differential jet cross section at mid-rapidity in pp collisions at $\sqrt{s} = 2.76$ TeV, with integrated luminosity of 13.6 nb$^{-1}$. Jets are measured over the transverse momentum range 20 to 125 GeV/c and are corrected to the particle level. Calculations based on Next-to-Leading Order perturbative QCD are in good agreement with the measurements. The ratio of inclusive jet cross sections for jet radii $R = 0.2$ and $R = 0.4$ is reported, and is also well reproduced by a Next-to-Leading Order perturbative QCD calculation when hadronization effects are included.
The possible existence of a "bubble" structure in the proton density of $^{34}$Si has recently attracted a lot of research interest. To examine the existence of the "bubble" structure in low-lying states, we establish a relativistic version of configuration mixing of both particle number and angular momentum projected quadrupole deformed mean-field states and apply this state-of-the-art beyond relativistic mean-field method to study the density distribution of the low-lying states in $^{34}$Si. An excellent agreement with the data of low-spin spectrum and electric multipole transition strengths is achieved without introducing any parameters. We find that the central depression in the proton density is quenched by dynamic quadrupole shape fluctuation, but not as significantly as what has been found in a beyond non-relativistic mean-field study. Our results suggest that the existence of proton "bubble" structure in the low-lying excited $0^+_2$ and $2^+_1$ states is very unlikely.
Using a relativistic transport model ART1.0, we explore effects of nuclear symmetry energy on eta meson production and its rare decay to the dark U-boson in heavy-ion reactions from 0.2 to 10 GeV/nucleon available at several current and future facilities. The yield of eta mesons at sub-threshold energies is found to be very sensitive to the density dependence of nuclear symmetry energy. Above a beam energy of about 5 GeV/nucleon in Au+Au reactions, the sensitivity to symmetry energy disappears. Using the branching ratio of the rare eta decay (eta->gamma U) available in the literature, we estimate the maximum cross section for the U-boson production in the energy range considered, providing a useful reference for future U-boson search using heavy-ion reactions.
XMASS, a low-background, large liquid-xenon detector, was used to search for solar axions that would be produced by bremsstrahlung and Compton effects in the Sun. With an exposure of 5.6ton days of liquid xenon, the model-independent limit on the coupling for mass $\ll$ 1keV is $|g_{aee}|< 5.4\times 10^{-11}$ (90% C.L.), which is a factor of two stronger than the existing experimental limit. The bounds on the axion masses for the DFSZ and KSVZ axion models are 1.9 and 250eV, respectively. In the mass range of 10-40keV, this study produced the most stringent limit, which is better than that previously derived from astrophysical arguments regarding the Sun to date.
The available experimental data on shell evolution indicate that the strength of the spin-orbit (SO) single-particle potential may be enhanced in neutron-rich nuclei. We observe that such a simple scheme destroys the Harmonic Oscillator (HO) magic numbers N=8 and 20 and generates new SO magic numbers like N=6, 14, 16, 32 and 34. The traditional SO magic numbers like N=28 and 50 and N=14 seen in $^{22}$O are eroded somehow in neutron-rich nuclei due to the sensitivity of larger-$l$ orbitals to the depth of the central potential but they are more robust than the HO magic numbers. The N=82 shell closure persists in neutron-rich nuclei while HO shell closures like N=40 and 70 do not emerge. Both mechanisms contribute to enhancing the N=56 and 90 gaps by splitting the $1d_{5/2}$ and $0g_{7/2}$ and the $0h_{9/2}$ and $1f_{7/2}$ orbitals.
With the availability of the new neutral pion photoproduction from the proton data from the A2 and CB-TAPS Collaborations at Mainz it is mandatory to revisit Heavy Baryon Chiral Perturbation Theory (HBChPT) and address the extraction of the partial waves as well as other issues such as the value of the low-energy constants, the energy range where the calculation provides a good agreement with the data and the impact of unitarity. We find that, within the current experimental status, HBChPT with the fitted LECs gives a good agreement with the existing neutral pion photoproduction data up to $\sim$170 MeV and that imposing unitarity does not improve this picture. Above this energy the data call for further improvement in the theory such as the explicit inclusion of the Δ(1232). We also find that data and multipoles can be well described up to $\sim$185 MeV with Taylor expansions in the partial waves up to first order in pion energy.