Exotic clustering in 222,224,226Ra

We describe the J^π = 0⁺, 2⁺, 4⁺, … ground state bands of ^222,224,226Ra, using a model in which these bands are treated as a ¹⁴C cluster orbiting the appropriate Pb core. For each isotope, we obtain good agreement with the measured half-life for the ¹⁴C decay of the 0⁺ ground state, as well as with the excitation energies and in-band E2 decays of other states of the ground state band. We also propose extensions of the model to deal with the observed low-lying J^π = 1⁻, 3⁻, 5⁻, … bands, their in-band E2 decays, and the E1 and E3 transitions connecting to the ground state bands.     

Exotic clustering in Ce and Nd isotopes

We propose exotic binary cluster models for the intermediate mass nuclei ^146,148,150Ce and ^{148,150,152,154}Nd. The optimum choice of cluster and core is determined by joint consideration of the penetrability for exotic cluster emission, the deviations of cluster and core binding energies from underlying liquid drop values and the Q-values for breakup. It is noticeable that the core neutron number selected in this way is at or near the N = 82 shell closure. We use a standard form of the cluster-core potential to calculate the energies and wave functions of states in the ground 0⁺, 2⁺, 4⁺, … and lowest lying negative parity 1⁻, 3⁻, 5⁻, … bands. The theoretical spectra and electromagnetic properties are compared with measurements, and their general trends are reproduced satisfactorily.     

Near barrier fission channels (Jπ, K) in 238U for spins Jπ=0+, 1−, and 2+ from (e,e′f) angular correlation measurements

Complete in- and out-of-plane fission fragment angular correlations for ²³⁸U have been measured in (e, e′f) coincidence experiments for momentum transfers q_eff=0.20 and 0.28 fm⁻ and excitation energies ω=5.5–15 MeV. A combined analysis with previously extracted E1 and E2/E0 multipole strength distributions yields strength distributions for all 6 near barrier fission channels (J^π, K) = (0⁺, 0), (1⁻, 0), (1⁻, 1), (2⁺, 0), (2⁺, 1), and (2⁺, 2) up to ≈8 MeV. An estim ate of the respective fission barriers, deduced from the increase of the fission cross sections, is given.     

Study of process e + e − → π+π−π0π0 at energies √s < 1 GeV with the spherical neutral detector

The cross section for the process e ⁺ e ^? → π⁺π^?π⁰π⁰ has been measured in an experiment with a spherical neutral detector, with the cross section at energies √s < 920 MeV having been measured for the first time. The model of vector dominance describes well the data obtained if the ρ, ρ′, and ρ″ resonances are taken into account. The probability of the decay ρ → π⁺π^?π⁰π⁰ is B(ρ → π⁺π^?π⁰π⁰) = (1.60 ± 0.74 ± 0.18) × 10^?5. The upper limit for the decay ω → π⁺π^?π⁰π⁰ has been improved by two orders of magnitude compared to previous measurements and is B(ω → π⁺π^?π⁰π⁰) < 2 × 10^?4 at a 90% confidence level.     

Collective bands in even mass Sn isotopes

Positive parity bands in ^{112, 114, 116, 118}Sn have been excited up to levels with spin and parity J^π = 12⁺ using Cd(α, 2nγ)Sn reactions. The experiments consisted of γ-ray excitation function, γ-γ coincidence, lifetime, γ-ray angular distribution, γ-ray linear polarization and conversion electron measurements. The observed bands show strong resemblances with ground-state bands of transitional nuclei in this mass region. It is pointed out that the J^π = 0⁺ band-heads originate from 2p-2h excitations in the Z = 50 proton shell. The excitation energies of the band-heads are calculated by means of the macroscopic-microscopic renormalization method. Pair correlations between the 2h and 2p configurations are included separately in a phenomenological way by taking into account the pairing energies of the Cd and Te ground states with respect to the Sn ground state.     

Study of π<Superscript>0</Superscript>/γ reconstruction and selection efficiency in the LHCb experiment

The reconstruction efficiency of photons and neutral pions is measured using the relative yields of reconstructed B ⁺ → J/ψK*⁺(→K ⁺π⁰) and B ⁺ → J/ψK ⁺ decays. The efficiency is studied using the data set, corresponding to an integrated luminosity of 3 fb^–1, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV.     

Study of π<Superscript>0</Superscript>/γ efficiency using B meson decays in the LHCb experiment

The reconstruction efficiency of photons and neutral pions is measured using the relative yields of reconstructed B ⁺ → J/ψK ^*+(→ K ⁺π⁰) and B ⁺ → J/ψK ⁺ decays. The efficiency is studied using the data set, corresponding to an integrated luminosity of 3 fb^–1, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV.     

Spin assignment of the 8.555 MeV state in28Si

Angular correlations between the gamma rays following the decay of the 8.555 MeV state in²⁸Si, known to have natural parity, were measured. The spin assignment of this state, found in this experiment, isJ ^π=6⁺. Energy sequence of the lowestJ ^π=2⁺, 4⁺ and 6⁺ states in²⁸Si compares well with the energy sequence of the ground state rotational bands in²⁰Ne and²⁴Mg.     

Spin parity structure of the Q and L enhancements in K−p → (K−π−π+)p at 10 and 16 GeV/c

A parital wave analysis of the (Kππ) system produced in K^?p → (K^?π^?π⁺)p at 10 and 16 GeV/c has been performed. It is found that in 88% of the cases the Kππ) system is in unnatural spin-parity (J^P) states 0^?, 1⁺, 2^? …, with contributions from many decay modes, $\text{κπ,}\text{K}{}^1\text{(890)π,}\text{K}{}^1\text{(1420)π,}\text{K}\text{?,}\text{K}\text{?}\text{and Kf}$. More than one decay m and J^P state are required to describe the Q and L enhancements, suggesting a composite structure of these enhancements. The (Kππ) system is produced dominantly (～95%) by natural parity exchange. Overall, the production mechanism of the (Kππ) system is remarkably similar to that of the 3π system in π^?p → (π^?π^?π⁺)p, even i detailed spin-parity structure.     

Electroexcitation of high spin states in 208Pb

The formfactors for the electroexcitation of the collective states of ²⁰⁸Pb have been calculated within the Model of Separable Residual Interaction (MSI); the results for the even parity states up to J^π = 10⁺ agree nicely with recent measurements. It turns out, that the energies of the lowest collective states of positive parity follow rather closely a J(J + 1) law.     

Effect of <Emphasis Type="Italic">Z′</Emphasis>-mediated flavor-changing neutral current on <Emphasis Type="Italic">B</Emphasis> → <Emphasis Type="Italic">ππ</Emphasis> decays

We study the effect of Z′-mediated flavor-changing neutral current on the B → ππ decays. The branching ratios of these decays can be enhanced remarkably in the nonuniversal Z′ model. Our estimated branching ratios B(B ⁰ → π ⁰ π ⁰) are enhanced significantly from their standard model (SM) value. For g′/g = 1, the branching ratios B(B ⁰ → π ⁰ π ⁰) are very close to the recently observed experimental values and for higher values of g′/g branching ratios are more. Our calculated branching ratios B(B ⁰ → π ⁺ π ^?) and B(B ⁺ → π ⁺ π ⁰) are also enhanced from the SM value as well as the recently observed experimental values. These enhancements of branching ratios from their SM value give the possibility of new physics.     

Structure of the mirror nuclei21Ne and21Na

Theγ-decay of levels in²¹Ne up to 10 MeV excitation energy has been investigated byn — γ coincidence measurements initiated with the¹⁸O(α, nγ) reaction at 12, 13, 14.5 and 15.4 MeV bombarding energies. Spin(-parity) assignments of excited states are obtained by combining then — γ angular correlation measurements performed atE _α=11, 11.82 and 13.6 MeV with a consideration of lifetimes, neutron penetrabilities of the unbound states, and information from the mirror nucleus²¹Na. The resulting values of E_x[keV]?J ^π are as follows: 4525-5⁺, 4686-3⁺, 5431-7⁺, 5549-3⁺, 5819-7^?, 6175-7⁺, 6268-9⁺, 6550-9, 6639-9, 7006-7⁺, 7041-9, 7356-7 or 9, 7422-11^(?), 7648-7⁺, 7981-11 or (7⁺), 8154-9, 8240-11, 8664-9^? or 11 or 13^?, 9401-13^?, 9867-13^? or 15⁺, 9941-13^? or 15 or 17⁺. The assignment of mirror levels in²¹Ne —²¹Na has been extended to the 6175 keV level of²¹Ne. Excitation energies, electromagnetic properties, Gamow?Teller matrix elements and spectroscopic factors of positive parity states are compared with the results of shell-model calculations which employ a unifieds—d shell Hamiltonian and the unrestricted configuration space of the 0d _5/2 —1s _1/2—0d_3/2 shell. Collective properties contained in shell model wave functions are explored up to the termination of bands atJ=17/2 or 19/2. The spectrum of intruder states in²¹Ne is observed to begin with a 5628 keV,J ^π=7/2⁺ state. The 7422, 8664 and 9401 keV levels are assigned as members of previously established negative-parity rotational bands.     

Mixed-symmetry states in the neutron-proton interacting boson model

States of mixed proton-neutron symmetry are investigated in different dynamical symmetries of the interacting boson model. We discuss in each of the limits the energy spectrum, the wave functions and the B(M1; 0₁⁺ → 1 _1⁺) values. We also study three classes of transitional nuclei namely the Pd nuclei [U(5) → O(6)], the Sm nuclei [U(5) → SU(3)] and the Pt nuclei [O(6) → SU(3)] with respect to the energy of the lowest non-symmetric J^π = 1⁺, 3⁺ levels as well as the M1 and M3 strengths for exciting these levels from the ground state. For ⁹⁸Pd we compare this calculation with a shell-model calculation. Finally, we adress the problem of the mixing of the non-symmetric J^π = 1⁺ state with nearby hexadecapole (g-boson) configurations.     

Isospin violation in the standard model and the decay F+ → π+π0

The decay F⁺ → π⁺π⁰ can proceed via isospin violating mechanisms similarly to $\text{ψ′ →}\text{J}\text{ψπ}{}^0$. I estimate that π⁰-η-′ mixing together with symmetry breaking in the amplitude lead to Γ(F⁺ → π⁺π⁰)/Γ(F⁺ → π⁺η) = (2.2 ± 0.7) × 10^?3 or (1.0 ± 0.3) × 10^?3, if annihilation processes dominate nonleptonic charmed meson decays. These values correspond to different assumptions for two-meson production in F decays.     

A study of the slope-mass correlation in the low mass K ππ system

The shape of the four-momentum transfer t′ distribution in the reactions K^±p→K^±π⁺π^?p at 13 GeV/c is studied for various partial waves as a function of the Kππ mass. Strong variation of the slope with effective mass is observed for the dominant J^P=1⁺ waves. For natural parity exchange it is found that, for Kππ masses up to 1.6 GeV, the slope of the t′ distribution is decreasing with increasing spin of the excited system, B₀?>B₁+>B₂⁺.     

A study of the low-lying states in 178Hf through the (n, γ) reaction

The nucleus ¹⁷⁸Hf was studied through thermal neutron and averaged resonance neutron capture reactions. The γ-ray and conversion electrons were measured with high resolution spectrometers. A level scheme up to an excitation energy of ∼2.1 MeV was constructed. It includes ∼65 levels, most of which are ordered into 18 rotational bands. The level scheme is complete up to about 1800keV for spins between 2 and 5. The neutron binding energy was established to be at 7626.3 (3) keV. The consistent Q form of the IBA-1 (CQF) was used to describe the low-lying collective γ and K^π = 0⁺ bands. The agreement with the data was found to be excellent for the energies and B(E2) ratios of the ground and γ bands, whereas the agreement was poor for the K^π = 0⁺ bands.     

Observation of structure in p̄p → π0π0

We present a partial wave amplitude analysis of the differential cross sections for p?p → π⁰π⁰ at 25 energies from 2.12 to 2.43 GeV. The results suggest the presence of a J^PCI^G = 2⁺⁺0⁺ resonance at 2.15 GeV. An isospin decomposition of p?p → π⁺π^- is also presented.     

Estimating of CP-violation in <Emphasis Type="Italic">B</Emphasis><Superscript>0</Superscript>→ψ(2<Emphasis Type="Italic">S</Emphasis>)π<Superscript>0</Superscript> decay

I present estimates of CP-violating asymmetries in the non-leptonic charmonium two-body B⁰→ψ(2S)π⁰ decay and the same decays of B⁺→ψ(2S)π⁺ and B⁺→ψ(2S)K⁺ These estimates are based on QCD and improved QCD factorization approach making use of next-to-leading order (NLO) contributions. The CP-violating asymmetry for B⁰→ψ(2S)π⁰ decay is not available, according to the same calculations, it is expected if it can be measured in the future its value will be S_ψ(2S)π0(B⁰ → ψ(2S)π⁰)= 0.662 ± 0.197 and C_ψ(2S)π0(B⁰ → ψ(2S)π⁰)= 0.024 ± 0.007.     

Evidence for the coexistence of spherical and deformed states in38Ar

The³⁸Ar levels at E_x=5350, 7289 and 9341 keV have been investigated using the³⁵Cl(α,pγ) reaction at E_α=l4 and 14.5 MeV. From particle-γ-ray angular correlations the spin assignments J(5350)=4, J(7289)=6,4 and J(9341)=8,6,4 have been obtained. Life-time measurements using the Doppler-shift attenuation method yielded τ(9341)=106±25 fs and τ(7289)=77±30 fs, while the lifetime τ(5350)=200±50 fs was known previously. All levels have positive parity and decay by enhanced E2 transitions. Hence we propose that they are the J^π=4⁺, 6⁺ and 8⁺ members, respectively, of a K^π=0⁺ rotational band which has the E_x=3377keV, J^π=0⁺ and the 3937 keV, J^π=2⁺ levels as further members. The enhancement of inband E2 transitions is 30 _?6 ⁺¹⁰ W.u. (4→2), 35 _?14 ⁺³⁰ W.u. (6→4) and 20–36 W.u. (8 → 6), respectively, yielding an average intrinsic quadrupole moment Q₀=850 _?125 ⁺²⁰⁰ mb. The moment of inertia is given by h²2θ=92 keV. The present data are in good agreement with the predictions of a deformed state in³⁸Ar that coexists with the spherical states.