Hyperfeinstrukturuntersuchung des 6p 2 P 3/2-Terms im Au I-Spektrum durch Resonanzstreuung von Licht

From about 6×10⁶ stoppingK ^?-meson reactions in the Saclay 80 cm hydrogen bubble chamber 70Σ ^?→Λe^?¯ν and 11Σ⁺→Λe⁺ν decays have been identified. The ratio of the vector to axial vector coupling constant has been determined,f ₁/g ₁=?0.22±0.28, consistent with the predictionf ₁=0 of the CVC-theory. The branching ratios for the two decay modes are,Γ(Σ ^?→Λe^?ν)/Γ(Σ^?→ all modes)=(0.69±0.12). 10^?4,Γ(Σ⁺→Λe⁺ν)/Γ(Σ⁺→ all modes)=(0.29±0.10). 10^?4. The ratio, Γ(Σ⁺→Λe⁺)/Γ(Σ^?→Λe^?v)=0.69±0.18, agrees with the phase space ratio, 0.61, therefore a theory that includes no second class currents is consistent with the data.     

Latest Results From the HypHI Experiments at GSI: Hypernuclear Spectroscopy with Heavy Ion Induced Reactions

The HypHI Phase 0 experiment with ⁶Li projectiles at 2 AGeV on a carbon target has been performed at GSI in order to demonstrate the feasibility of hypernuclear spectroscopy with induced reaction of heavy ion beams. Current data analyses have shown peaks in invariant mass distributions of p + π ^? for Λ, ³He+ π ^? for ³ _Λ H and ⁴He + π ^? for ⁴ _Λ H. Lifetime values for the corresponding peaks have been also deduced, which are in good agreement with the former known values.     

Some tips on the decomposition of tensor product representations of compact connected lie groups

Let ?₁, ?₂, ?₃, ?₄ be irreducible representations of a compact connected semisimple Lie group G with highest weights Λ₁, Λ₂, Λ₃, Λ₄, respectively. Let ?₁?₂ (resp. ?₃?₄) be irreducible representations of G with highest weights Λ₁·Λ₂ (resp. Λ₃·Λ₄). It is assumed that one knows the Clebsch-Gordan series of ?₁??₃ and ?₂??₄ (resp. of S²?₁, S²?₂, A²?₁ and A²?₂). Then we formulate a result (Theorem 2) which gives information on the decomposition of ?₁?₂??₃?₄ (resp. of S²(?₁?₂) and A²(?₁?₂)). Though this result is not complete, it is useful because it delivers the information very quickly and in a very simple manner.     

Pi-mesic decays of A = 4 hypernuclei

Angular distributions and energy spectra for the decay modes _Λ⁴He→π^?p³He, _Λ⁴H → π^?p³H, _Λ⁴H → π^?n³He are calculated and compared with experiment. Final state nuclear interactions have been adjusted to fit the corresponding scattering data. With S-, P- and D-wave interactions we were able to obtain reasonably good agreement with the experimental decay spectra. It is suggested that the _Λ⁴H → π^?n³He decay spectra may be decisive in selecting the right set of p³H complex phase shifts from several possible solutions.     

Oscillator spacing and the probability for the recoilless Λ-production in nuclei

The relative contribution of the recoilless and quasifreeΛ-production in the (K^?,π^?) strangeness exchange reaction in nuclei is estimated by using the nuclear Debye-Waller factor. The expressions for theΛ-oscillator spacing ?ω_Λ needed for such an estimate are derived by means of procedures which lead to quite simple formulae for ?ω_Λ as function of the mass number and are useful in obtaining improved results.     

SU(3) lattice Monte Carlo calculation of the glueball mass spectrum

We have calculated the glueball masses of various spins and parities in SU(3) gauge theory. Our first results give m_M(0⁺⁺)=(3.6±0.2)Λ_mom, m_E(0⁺⁺)=(4.3±0.3)Λ_mom, m(0^?+)=(7.2_?0.9^+1.6)Λ_mom, m_M(2⁺⁺)=(8.1±1.1)Λ_mom and m_E(2⁺⁺)=(8.3_?1.0^+1.6)Λ_mom as well as information on the glueball wave functions.     

The non-mesonic to π− mesonic decay ratio and Λ-neutron stimulation fraction for p-shell hypernuclei

Kinematic analysis of simple hypernuclear production reactions has produced a sample of hypernuclei of _ΛB, _ΛC and _ΛN with negligible background, and a much smaller sample of _ΛBe. The values of the non-mesonic to π^? mesonic ratio Q^? for the above samples are 5.5 ± 0.5 and 4.3 ± 1.1, respectively. A sub-sample of ¹¹_ΛB hypernuclei was separated on the basis of production via an excited state of _Λ¹²C, giving Q^? = 4.8 ± 1.1 for _Λ¹¹B. Assuming the Fermi gas model is applicable to nuclei of mass A ≈ 11, two independent means of analysis of the non-mesonic decays give values for the Λ-neutron stimulation fraction n of 0.41 ± 0.09 and 0.34 ± 0.07 for hypernuclei of charge 5 ≦ Z ≦ 7.     

A measurement of the lifetime of the Λ3 H hypernucleus

The mean lifetime of the hypernucleus _Λ³H has been measured in a helium bubble chamber with the result, τ(_Λ³H)=(2.46_?0.41^+0.62)×10^?10 sec, based on 16 examples of the decay mode _Λ³H→π^?+³He and 24 examples of the decay mode _Λ³H→π^?+p+d. The decay branching ratio R₃ = Γ(_Λ³H → π^?+^{3He)/Γ(_Λ3H → all π? modes}) has been estimated to be 0.30 ± 0.07.     

Luminescence quenching of cyclometalated Pt(II) complexes by halogenide ions

The luminescence quenching of [Pt(CΛN)En]ClO₄ complexes ((CΛN)^? = ppy^?, tpy^?, and bt^? are deprotonated forms of 2-phenylpyridine, 2(2′-thienyl(pyridine), and 2-phenylbenzothiazole, respectively; En is ethylenediamine) by halogenide ions (Hal^? = Cl^?, Br^?, I^?) in ethanol solutions is studied. It is shown that the quenching has a dynamic character and its bimolecular rate constants are consistent with the enhancement of nonradiative deactivation of the excited state of {[Pt(CΛN)En]*...Hal} collision complexes with increasing spin-orbit interaction constant of the halogen.     

Hypernuclear spectroscopy in the p shell

A comprehensive shell-model approach to Λ-hypernuclear spectroscopy in the p shell is developed. The available data on the spectra of ⁹_ΛBe, ¹²_ΛC, ¹³_ΛC, ¹⁴_ΛN and ¹⁶_ΛO are interpreted in this framework, leading to constraints on the residual ΛN interaction and the one-body Λ-nucleus potential. The mechanism for the formation of Λ hypernuclei via the (K^?, π^?) reaction is treated in the relativistic distorted wave approximation, with careful attention paid to Fermi-averaging of the elementary K^?n → π^?Λ amplitude and recoil corrections. Departures from the simple weak coupling picture, arising from configuration mixing, are emphasized. This leads to approximate dynamical symmetries in hypernuclei which are forbidden in ordinary nuclei by the Pauli principle. Further experiments in the p shell are suggested which may reveal other aspects of ΛN interactions.     

Experimental study of the final state interactions in the decays of 4ΛH → π−p3H amd 4ΛHe → π−p3He

Experimental results concerning the decay modes _Λ⁴H → π^?p³H and _Λ⁴He → π^?p³He are presented. A sample of _Λ⁴He → π^?p³He decays almost free from a contamination of other hypernuclear decay modes was selected. Some experimental distributions are compared with theoretical predictions.     

CP violation with beautiful baryons

CP violation can be studied in modes of charmed or bottom baryons when a decay process is compared with its charge-conjugated partner. It can show up as a rate asymmetry and in a study of other decay parameters. Neither tagging nor time-dependences are required to observeCP violation with modes of baryons, in contrast to the conventionalB ⁰ modes. Numerous modes of bottom baryons have the potential to show largeCP-violating effects within the Standard Model. Those effects can be substantial for modes with aD ⁰, which is seen in a final state that can also be fed from a \(\bar D^0 \) . For instance, a comparison of theΛ _b→Λ _CP ⁰ with the \(\bar \Lambda _b \to \bar \Lambda D_{CP}^0 \) process can show sizeableCP violation. HereD _CP ^o denotesCP eigenstates ofD ⁰, which occur at a few percent. Six related processes, such asΛ _b→ΛD ⁰, \(\Lambda _b \to \Lambda \bar D^0 \) ,Λ _b→Λ _CP ⁰ , and their charge-conjugated counterparts, can extract ?, which is the most problematic angle of the unitarity triangle and which is conventionally probed with theB _s→ρ⁰ K _S asymmetry. HereD ⁰ andD ^?0 are identified by their charged kaon or lepton. We predictB(Λ _b→ΛD ⁰)～10^?5, thusB(Λ _b→Λ _CP ⁰ )～10^?7. Under favourable circumstances,CP violation can occur at the few tens of percent level. Thus 10²–10³ Λ _b→Λ _CP ⁰ decays start probing ?. Tables list many additional modes with typical branching ratios at the 10^?5–10^?6 level, with large detection efficiencies (in contrast to theD _CP ⁰ ), and with potentially largeCP-violating effects, such as Ξ _b ⁰ →ΛΨ, Λ?, ΛK^*0; Ξ _b ^? →ΛK^(*)?, Ξ^?K_s, Ξ^?K^*0, Ω _b ^? →Ξ^?φ, Ξ^?ρ⁰, ΛK^(*)?, ΩK_s, Ω^?K^*0.     

Investigation of the decay of charmed particles produced in neutrino interactions

The decay of charmed particles produced by high-energy neutrinos has been studied by an experiment using simultaneously emulsion, bubble chamber and counter techniques. Eight charmed particle candidates, 5 positively charged and 3 neutral, have been found in the emulsion, where their production and decay have been directly observed. One of these events is identified as a Λ_c⁺ baryon of mass 2.26±0.02 GeV/c² which undergoes the decay Λ_c⁺→pK^?π⁺ after a proper time of (7.3±0.1) · 10^?13 s.A statistical analysis of the other observed decays leads to the mean-life values τ⁺=(2.5_?1.1^+2.2) · 10^?13 s, τ⁰=(0.53_?0.25^+0.57) · 10^?13 s, for the sample of charged particles enriched by a similar event found in a previous experiment, and for the sample of 3 neutral particles, respectively. The former value is only slightly affected by including in the sample the Λ_c⁺ event or excluding that of the previous experiment.     

A note on the origin of secondary hypernuclear γ-quanta from Λ 10 B

An alternative interpretation of _Λ ¹⁰ B secondaryγ-quanta due to _Λ ¹⁰ B → _Λ ⁷ Li+³He channel is proposed. Its impact on effectiveΛN interaction properties and on understanding of (s ^?1 s _Λ) configurations is discussed and some verifying experiments are put forward.     

The formation of,and the γ-radiation from,the p-shell hypernuclei

The physical factors relevant for the production of various low-lying Λ-hypernuclear states ${}_{\mathrm{\Lambda }}{}^{\mathrm{A}}\text{Z}{}^1$ through the K^? → π^? and K^? → π⁰ reactions, in flight or from rest, on the corresponding target nuclei ^AZ and ^A(Z + 1) are discussed, on the basis of the shell model for these nuclei and hypernuclei, together with the characteristics of the dominant γ-transitions resulting from the excited states thus produced. Detailed consideration is given for a number of hypernuclei of specific interest, including the cases of _Λ⁷He, _ΛLi for A = 7, 9 and 10, _ΛBe for A = 9 and 10, _ΛB for A = 10, 11, and 12, _ΛC for A = 12, 13, 14, and 15, _ΛN for A = 14 and 15, and _Λ¹⁶O. The importance of (γ, π^?) correlation studies for the determination of hypernuclear spin values is stressed, with the discussion of several examples.     

Excitation and structure of hypernuclear resonances in (K −,π ¯0)-reactions on 1p-shell nuclei

The available experimental data on the excitation functions (EF) of the 1p-shellΛ-hy-pernuclei in (K ^?, π^?) reactions atθ _π = 0^° has been analysed in terms of shell model and weak coupling scheme. It is substantiated by the experimental data on the neutron spectroscopic factors and on the fragmentation of nuclear hole excitations. The pronounced nuclear spectroscopic characteristics in the hypernuclear spectra are indicative of a weak coupling ofΛ-hyperon with nuclear subsystem. The analysis has made it possible to determine the difference is single-particle energies ofΛ-hyperon in the 1p- and 1s-states and to obtain additional evidence for the smallness of theΛ-nucleus spin-orbit interaction. The resonance structure of EF of hypernuclei, which were not studied in (K ^?,π ₀ ^? ) reactions, is predicted. The interrelated aspects of the studies of the (K ^?,π ₀ ^? ), (K ^?,π ₀ ^? β^′), and (K ^?, π⁺) reactions which are of interest to spectroscopy ofΛ-andΣ-hypernuclei are discussed.     

The glueball mass spectrum in QCD: First results of a lattice Monte Carlo calculation

We perform a variational calculation of the masses of glueballs of various spins and parities in SU(2) gauge theory. The quantum vacuum we use is generated by the lattice Monte Carlo technique. Our first results, obtained on medium sized lattices give m(0⁺) = (3.6 ± 0.35) Λ_mom, m(0^? = (6.0 ± 1.0)Λ_mom, m(2⁺) = (6.5^+1.8_?1.1)Λ_mom, various mass upper bounds and information on glueball wave functions.     

Charm production in 400 GeV/c proton-emulsion interactions: Bombay-Chandigarh-Delhi-Jammu Collaboration

5032 proton-emulsion interactions at 400 GeV/c momentum have been carefully scrutinized for production and decay of charged charm particles. In order to detect these decays, shower tracks from 3056 stars have been followed to a maximum length of 1 mm and those from 1976 stars up to 2 mm. A total of 23 three-prong charm-like candidates have been recorded in the forward cone. The background due to γ-overlap on a shower track, trident/pseudo-trident production and secondary interactions is estimated to be 15. Attributing the signal of 8 events to Λ_c⁺ and assuming the branching ratio of Λ_c⁺ → 3 prong to be 0.6 and τ_Λc to be 10^?13 sec we obtain the production cross section to be 106±39μb/nucleon. Out of these 8 events one example of semileptonic decay of Λ_c⁺ is seen.     

Study of quasi two-body final states in K−n reactions at 8.25 GeV/c

Cross sections for various channels in 3 prong + V₀ final states of K^?n interactions are obtained at 8.25 GeV/c. An energy dependence study of the quasi two-body reactions Σ^?(1385) + vector meson and ΛB^? seem to imply the presence of cuts in the Regge exchange formalism, whereas the reaction Δ(1236) $\text{K}$¹ (890) does not require such cuts. Upper limits of 1 and 2 μb are found for the reactions K^?n → ΛA₁ and K^?n → ΛA₂.     

Measurements of the reaction K−n → π−Λ in the C.M.S. energy range 2050 MeV to 2175 MeV and partial-wave analysis of this reaction between 1875 MeV and 2175 MeV

New bubble chamber data on the reaction K^?n → π^?Λ in the c.m.s. energy range 2050 MeV to 2175 MeV are presented. These new data have been combined with published data on this reaction and on the reaction K^?p → π⁰Λ and a partial-wave analysis has been carried out between 1875 MeV and 2175 MeV. Parameters of the established resonances in this c.m.s. energy region have been determined and further evidence is presented for the existence of a Σ resonance with mass around 2100 MeV/c² in the P₃ partial wave.