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1.
To help the difficult determination of the angle γ of the unitarity triangle, Aleksan, Dunietz and Kayser have proposed the modes of the typeK ? D s + , common toB s and $\bar B_s $ . We point out that it is possible to gain in statistics by a sum over all modes with ground state mesons in the final state, i.e.K ? D s + ,K *? D s + ,K ? D s *+ ,K * D s * . The delicate point is the relative phase of these different contributions to the dilution factorD of the time dependent asymmetry. Each contribution toD is proportional to a product $F^{cb} F^{ub} f_{D_s } f_K $ whereF denotes form factors andf decay constants. Within a definite phase convention (i.e. for example the one defined by the heavy quark symmetry in the limit of heavy quarks), lattice calculations do not show any change in sign when extrapolating to light quarks the form factors and decay constants. Then, we can show that all modes contribute constructively to the dilution factor, except theP-waveK * D s *+ , which is small. Quark model arguments based on wave function overlaps also confirm this stability in sign. By summing over all these models we find a gain of a factor 6 in statistics relatively toK ? D s + . The dilution factor for the sumD tot is remarkably stable for theoretical schemes that are not in very strong conflict with data onB→ψK(K *) or extrapolated from semileptonic charm form factors, givingD tot≥0.6, always close toD(K ? D s + ).  相似文献   

2.
We investigate the effects of final state interactions (FSI) contributions in the nonleptonic two body $B^ + \to D_S^ + \bar K^0$ decay, however the hadronic decay of $B^ + \to D_S^ + \bar K^0$ is analyzed by using “QCD factorization” (QCDF) method and final state interaction (FSI). First, the $B^ + \to D_S^ + \bar K^0$ decay is calculated via QCDF method and only the annihilation graphs exist in that method. Hence, the FSI must be seriously considered to solve the $B^ + \to D_S^ + \bar K^0$ decay and the D 0π+(D 0+), D +π0(D +0) and D +η c (D +*J/ψ) via the exchange of K +(*), K 0(*) and D s +(*) mesones are chosen for the intermediate states. To estimate the intermediate states amplitudes, the QCDF method is again used. These amplitudes are used in the absorptive part of the diagrams. The experimental branching ratio of $B^ + \to D_S^ + \bar K^0$ decay is less than 8 × 10?4 and the predicted branching ratio is 0.23 × 10?9 in the absence of FSI effects and it becomes 6.74 × 10?4 when FSI contributions are taken into account.  相似文献   

3.
InclusiveK s 0 andK s 0 K s 0 production in \(\bar pp\) interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c are studied. Cross sections ofK s 0 , K s 0 K s 0 andK (892) are presented for each incident momentum. The production ofK s 0 andK (892) through annihilation process is investigated. It is found that the annihilation process is dominant but decreases with incident momentum. The annihilation process is compared withe + e ? interactions. Remarkable similarity between them is found in the \({{x_0 = 2E(K_s^0 )} \mathord{\left/ {\vphantom {{x_0 = 2E(K_s^0 )} {\sqrt s }}} \right. \kern-0em} {\sqrt s }}\) distribution. Events with two detectedK s 0 's are analyzed. The result shows theK s 0 K s 0 pairs are produced in the central region of c.m. system and there is a clearS * signal in theK s 0 K s 0 effective mass distribution.  相似文献   

4.
The diffractive production of charmed strangeD s * and possiblyD s mesons by neutrinos and antineutrinos on nucleons in hydrogen, deuterium and neon targets is observed. The slope parameter of thet distribution is 3.3±0.8 (GeV)?2. The production rate per charged current neutrino interaction with an isoscalar target times the D s + →φτ+ branching fraction is (1.03±0.27)×10?4.  相似文献   

5.
We have performed a two-channel calculation of Cabibbo-angle favoured decays,D s + →VP. We find a satisfactory fit toS s + φπ +,ρ 0 π + andK + \(\bar K^{ * 0} \) data from ARGUS and E-691. We have also studied Cabbibo-angle favouredD→VP decays in a coupled channel formalism. We coupleDK *π,K ? and \(\bar K^0 \phi \) channels inI=1/2 state, andK *π andK ? channels inI=3/2 state. We leave the two channels, \(\bar K^0 \omega \) and \(\bar K^{ * 0} \eta \) out of our unitarization scheme. Particular attention is paid to the role of the weak annihilation term in these decays.  相似文献   

6.
It is numerically shown that the groundstate of the Friedel problem (consisting of a conduction band and a dresonance), occupied with (n+ 1) electrons, can be written as Ψ = (A a 0 * +Bd*) Π v=1 n a v * Φ0, where a 0 * represents a localized conduction electron state, d* is the Friedel resonance state and Π v=1 n a v 8 Φ0 is a Slater determinant of n single electron states a t * , (Φ0 is the vacuum state). The a i * together with a 0 * are part of a full ortho-normalized basis of the conductions band.  相似文献   

7.
Using the experimentally measured values ofx=A 2(0)/A 1(0) andy=V(0)/A 1(0) and the measured ratiosR st=Γ(D s + φl + ν l)/Γ(D ins + φπ +) andR h=Γ(D s + φρ +)/Γ(D s + φπ +), we present evidence for significant nonfactorization contribution in the decay amplitude forD s + φπ +. We analyze the role of nonfactorization inD s + φρ + and conclude that present data onR h are consistent with factorization inD s + φρ +. A measurement of polarization inD s + φρ + would greatly assist our analysis.  相似文献   

8.
The inclusive production ofK s 0 , Λ and \(\bar \Lambda \) particles is investigated in 70 GeV/c \(\bar pp\) interactions in an experiment performed at CERN using BEBC equipped with a TST. Differential cross-sections are studied and compared with corresponding data at surrounding energies. Differences withpp data obtained at the same energy allow an estimate of theK s 0 , production cross-section in annihilation processes. Evidence is also given for central \(\Lambda \bar \Lambda \) production.  相似文献   

9.
We have carried out a study of Cabbibbo-favored two-body decays ofD 0 andD s + involving η and η′ in the final state, $D^0 \to (\eta ,\eta ')\bar K^0 , D^0 \to (\eta ,\eta ')\bar K*^0 $ andD s + →(η,η′)π +,D s + →(η,η′)ρ +. We have introduced an annihilation term wherever admissible, and investigated its size if it were to bridge the gap between theory and experiment in each case. We have also related the semileptonic rates forD s + →(η,η′)e + v to those of the hadronic rates forD s + →(η,η′)π + and unveiled a puzzle. We offer a possible solution.  相似文献   

10.
The asymmetry between the spectra of leading and nonleading charmed mesons that was measured in Σ? A interactions at p L=340 GeV/c in the WA89 experiment is described within the Model of Quark-Gluon Strings (QGS model also known as QGSM) under the assumption that there is a fraction of charmed sea quark-antiquark pairs (intrinsic charm) in an interacting hyperon. It is shown that the asymmetries between D ?-and D +-meson spectra and between D s ? -and D s + -meson spectra can be approximated by QGSM curves obtained with the same string-fragmentation parameter, a 1=10, and the same intrinsic-charm fraction, $\delta _{c,\bar c} = 0.01$ , as those that were used in describing D s ? /D s + -meson asymmetry of π? A experiments in previous studies. The asymmetry between the spectra of Λc and $\bar \Lambda _c $ that was measured in Σ? A collisions at p L=600 GeV/c in the E781 experiment is also described within this scheme. The QGSM results are compared with the results of the calculations in the next-to-leading approximation of perturbative QCD that were performed by other authors.  相似文献   

11.
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 bΛ 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 bΛD 0, \(\Lambda _b \to \Lambda \bar D^0 \) ,Λ bΛ 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 bΛD 0)~10?5, thusB(Λ bΛ CP 0 )~10?7. Under favourable circumstances,CP violation can occur at the few tens of percent level. Thus 102–103 Λ bΛ 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?Ks, Ξ?K*0, Ω b ? →Ξ?φ, Ξ?ρ0, ΛK(*)?, ΩKs, Ω?K*0.  相似文献   

12.
Spin effects in the weak two-body hadronic decays of the B c and B c * mesons into J/ψ and ρ(π) mesons are considered within the model of hard one-gluon exchange between quarks at high momentum transfers. It is shown that the polarization of the J/ψ meson in the decays of the B c * meson differs substantially from that in the decays of the B c * meson. The decay widths of the B c * meson differ significantly from the widths of the B c * meson.  相似文献   

13.
Pionic deuterium     
The strong-interaction shift ε 1s πD and broadening Γ 1s πD in pionic deuterium have been determined in a high statistics study of the πD(3p-1s) X-ray transition using a high-resolution crystal spectrometer. The pionic deuterium shift will provide constraints for the pion-nucleon isospin scattering lengths extracted from measurements of shift and broadening in pionic hydrogen. The hadronic broadening is related to pion absorption and production at threshold. The results are ε 1s πD = (?2356 ± 31) meV (repulsive) and Γ 1s πD meV yielding for the complex πD scattering length a πD = [?(24.99±0.33)+i(6.22 ?0.26 +0.12 )] × 10?3 m π ?1 . From the imaginary part, the threshold parameter for pion production is obtained to be α = (251 ?11 +5 ) μb. This allows, in addition, and by using results from pion absorption in 3He at threshold, the determination of the effective couplings g 0 and g 1 for s-wave pion absorption on isoscalar and isovector NN pairs.  相似文献   

14.
We analyze a discrete phenomenological model accounting for phase transitions and structures of polar Smectic-C* liquid-crystalline phases. The model predicts a sequence of phases observed in experiment: antiferroelectric SmC A * –ferrielectric SmC FI1 * –antiferroelectric SmC FI2 * (three-and four-layer periodic, respectively)–incommensurate SmC α * –SmA. We find that, in the three-layer SmC FI1 * structure, both the phase and the module of the order parameter (tilt angle) differ in smectic layers. This modulation of the tilt angle (and therefore of the layer spacing d) must lead to X-ray diffraction at the wave vectors Q s =2πs/d(s=n±1/3) even for the nonresonant scattering.  相似文献   

15.
The exclusive decay of B +D + K 0 is calculated by the QCD factorization method (QCDF) and final state interaction (FSI). First, the B +D + K 0 decay is calculated via QCDF method. The result that is found by using the QCDF method is less than the experimental result. So FSI is considered to solve the B +D + K 0 decay. For this decay, the D s + π0, D s + 0, D s + *? via the exchange of \(\bar K^0\) , \(\bar K^{0*} \) , D ?, and D ?* mesons are chosen for the intermediate states. The above intermediate states are calculated by using the QCDF method. In the FSI effects, the results of our calculations depend on η as the phenomenological parameter. The range of this parameter is selected from 2 to 2.4. It is found that if η = 2.4 is selected, the numbers of the branching ratio are placed in the experimental range. The experimental branching ratio of this decay is less than 2.9 × 10?6 and our results calculated by QCDF and FSI are (0.16 ± 0.04) × 10?6 and (2.8 ± 0.09) × 10?6, respectively.  相似文献   

16.
We present a study of the inclusive production ofK *(892) and ∑t+-(1385)+cc at 3.6 GeV/c from \(\bar p\) p interactions. The sensitivity of the exposure is 35.4 events/μb. Longitudinal and transverse momentum distributions are presented. The indirect production ofK s 0 from parentK * and that of Λ's from parent Σ(1385) are studied. The shape of thex distribution of Λ's for \(p\xrightarrow{{\bar p}}\Lambda \) are calculated from \(p\xrightarrow{p}\Lambda \) and \(p\xrightarrow{{\pi ^ - }}\Lambda \) and compared with the experimental distributions. The difference of antiparticle production cross-section ofK s 0 in the central region is compared with the expectation from Mueller-Regge formalism.  相似文献   

17.
A simple idea about quark-quark or quark-diquark reaction mechanism is proposed to predict thex F spectra in \(\bar p\) p interactions. Over a wide energy range, it is applied to the strange particle production in \(\bar p\) interactions and found that it reproduces well thex F spectra of strange particleK s 0 ,K *± ,Ε 0 andΣ +(1385) productions, especially, including the leading effect in the case of strange baryonΕ 0,Σ +(1385) productions.  相似文献   

18.
19.
Starting from an isospin invariant shell-model hamiltonian, we describe a method for deriving microscopically the IBM-hamiltonian appropriate to lights d-shell nuclei. The key ingredients of our approach are:a) the Belyaev-Zelevinsky-Marshalek (BZM) bosonization procedure;b) two successive unitary transformations that extract the “maximally decoupled” collective bosons with angular momentaJ=0(s ππ + ,s νν + ,s πν + ) andJ =2(d ππ + ,d νν + ,d πν + (T=0),d πν + (T=1)). The method is applied to obtain the low-energy spectra and the electron scattering form factors for the 0 1 + →2 1 + transitions in20Ne and24Mg. Good agreement with the exact shell-model results is achieved. The inclusion of proton-neutron bosons (s πν + ,d πν + (T=1),d πν + (T=0)), as well as the renormalization of boson parameters due to the non-collective degrees of freedom, are shown to play a crucial role.  相似文献   

20.
The pulsed electron electron double resonance (PELDOR) pulse sequence is applied to a three-spin system consisting of three radicals (Y D · , Y Z · and Q A ? ) generated in spinach PS II. The distance between YZ and QA has been determined to be 3.4 nm with the previously derived distances of the other radical pairs, 2.9 nm for Y D · -Y Z · and 3.9 nm for Y D · -Q A ? . This distance has been derived from the Y Z · -Q A ? radical pair trapped in YD-less mutants ofChlamydomonas reinhardtii. Furthermore the method was applied to the Y D · -Q A ? -Chl Z + system to find the unknown distance between QA and ChlZ. The derived distance was 3.4 nm. A triangular configuration was found in the membrane system that gives the relative positions of the electron transfer components.  相似文献   

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