Weak interaction effects in positronium

Within the context of the Weinberg-Salam (standard) model we study possible effects of weak interactions in positronium (Ps), such as parity mixing and weak decays of Ps states. As expected, weak interaction amplitudes in Ps turn out to be extremely small, their magnitude being characterized byG·m _e ² ?3·10^?12 whereG is Fermi's constant andm _e the electron mass. We show that the standard model forbids parity-violating correlations in a large class of Ps reactions and decays due to CP conservation in the lepton sector. We then consider situations in which parity-odd effects in Ps will occur in the standard model and may even be large enough to be observable. Beyond the context of the standard model we discuss the decay of orthopositronium into a photon and the hypothetical axion under the assumption that the mass of the axion is smaller than twice the mass of the electron.     

核心天线CP43、CP47的荧光光谱特性

采用快速扫描成象光谱技术对核心天线CP43和CP47的荧光光谱特性进行研究,获取了它们的积分荧光谱,通过积分荧光谱的组分光谱解析,并结合吸收光谱分析认为CP43和CP47具有这样的Chla的光谱特性,CP43:Chla₆₆₀^662.43、Chla₆₆₉^670.23、Chla₆₈₂^684.02,CP47:Chla₆₆₀^664.91、Chla₆₆₉^671.71、Chla₆₈₀^681.35、(Chla_a^e,a代表吸收峰;e代表发射峰);另外长波长组分694.86nm、702.34nm(CP43)、696.02nm(CP47)可能是由吸收>690nm的Chla分子所产生;CP43与CP47相比还存在有Chla₆₇₅^676.32,但是还没有看到CP43具有675nm吸收谱带的报道.对CP43和CP47的荧光光谱分析,认为CP47中的Chla669nm分子团和Chla680nm分子团间的能量传递比CP43中Chla669nm和Chla682nm分子团的能量传递更为有效;β-Car与Chla分子结合状态在CP47中要比CP43中紧密.     

Excited state positronium formation in low density gases

Excited state Ps atoms formed in low density Ne, Ar and H₂ gases have been observed for the first time. The maximum yield was estimated to be ≈ 5.7 × 10^?2 excited Ps atoms per stopped positron of energy ≈ 16 eV in H₂. This is about 14 times greater than previous maximum yields.     

光系统Ⅱ核心复合物激发能传递光谱特性

采用ICCD皮秒、飞秒扫描成象光谱装置研究PSⅡ核心复合物激发能传递光谱特性,获得的PSⅡ积分荧光谱从661nm到693nm,峰值波长680nm,有四个组分谱,谱的峰值分别为670nm、676nm、681nm、686nm.CP43有Chla₆₆₀⁶⁶¹、Chla₆₆₉⁶⁷⁰和Chla₆₈₂⁶⁸⁶三个光谱组分;CP47有Chla₆₆₀⁶⁶¹、Chla₆₆₉⁶⁷⁰和Chla₆₈₀⁶⁸¹三个光谱组分.根据吸收光谱和组分光谱分析,PSⅡ核心天线各自有三种不同状态的Chla分子,它们是CP43-Chla₆₆₀⁶⁶¹、CP43-Chla₆₆₉⁶⁷⁰、CP43-Chla₆₈₂⁶⁸⁶与CP47-Chla₆₆₀⁶⁶¹、CP47-Chla₆₆₉⁶⁷⁰、CP47-Chla₆₈₀⁶⁸¹.通过四个光谱组分分析了PSⅡ核心复合物激发能传递的光谱特性.     

Differential calculus on quantum projective spaces

Covariant first order differential calculus on the quantum projective spaces CP _q ^N-1 is studied by two approaches. First, the embedding of CP _q ^N-1 into the quantum spheres S _q ^2N-1 is used to obtain differential calculi on CP _q ^N-1 by restriction; second, classification results for differential calculi on CP _q ^N-1 under three different constraint settings are proved directly. The main results are that under each of the constraints considered, there exists a differential calculus which is uniquely determined if N 6, and that (essentially) all of the differential *-calculi on S _q ^2N-1 known from a previous classification paper admit restriction to CP _q ^N-1 .     

Doubly Excited <Superscript>1,3</Superscript><Emphasis Type="Italic">P</Emphasis><Superscript>e</Superscript> Resonance States of the Positronium Negative Ion with Coulomb and Screened Coulomb Potentials

We have investigated the doubly excited ^1,3 P ^e resonance states of positronium negative ion with Coulomb and screened Coulomb potentials using highly accurate correlated exponential wavefunctions. For Coulomb interaction, the stabilization and the complex-rotation methods are employed to extract resonance parameters (resonance positions and widths). We have obtained two ¹ P ^e resonances and three ³ P ^e resonances below the n = 3 Ps threshold. In addition to Feshbach resonances lying below n = 3 Ps threshold, we have calculated one ³ P ^e shape resonances lying above the Ps (n = 2) threshold. For screened Coulomb (Yukawa) interaction, we employ the stabilization method to extract resonance parameters as functions screening parameter. The resonance energies and widths for ^1,3 P ^e resonance states of Ps⁻ below the n = 3 Ps threshold for different screening parameters ranging from infinity (Coulomb case) to small values are reported, along with the Ps(3S) and Ps(3P) threshold energies. The screened Coulomb results for the ^1,3 P ^e resonance states are reported for the first time in the literature.     

On puzzles and non-puzzles in B→ππ,πK decays

Recently, we have seen interesting progress in the exploration of CP violation in B⁰ _d→π⁺π^-: the measurements of mixing-induced CP violation by the BaBar and Belle collaborations are now in good agreement with each other, whereas the picture of direct CP violation is still unclear. Using the branching ratio and direct CP asymmetry of B⁰ _d→π^-K⁺, this situation can be clarified. We predict , which favours the BaBar result, and we extract γ=(70.0^+3.8 _-4.3)^°, which agrees with the unitarity triangle fits. Extending our analysis to other B→πK modes and B⁰ _s→K⁺K^- with the help of the SU(3) flavour symmetry and plausible dynamical assumptions, we find that all observables with colour-suppressed electroweak penguin contributions are measured to be in excellent agreement with the standard model. As far as the ratios R_c,n of the charged and neutral B→πK branching ratios are concerned, which are sizeably affected by electroweak penguin contributions, our standard-model predictions have almost unchanged central values but significantly reduced errors. Since the new data have moved quite a bit towards these results, the “B→πK puzzle” for the CP conserving quantities has been significantly reduced. However, the mixing-induced CP violation of B⁰ _d→π⁰K_S does look puzzling; if confirmed by future measurements, this effect could be accommodated through a modified electroweak penguin sector with a large CP violating new-physics phase. Finally, we point out that the established difference between the direct CP asymmetries of B^±→π⁰K^± and B_d→π^∓K^± appears to be generated by hadronic and not by new physics.     

CP violation in decay rates of charged bottom mesons

In the standard theory we discuss a mechanism of interference between two different tree-level charged current amplitudes to induce CP violation. The asymmetry between conjugate Cabibbo disfavoured modes of charged bottom meson decays is considered. Estimates for two-body decays ofB _u andB _c are presented. We find thatB _u ^? →D ^?+D ₀ ^* , for instance, can give a big CP asymmetry with values ≈1–50%, depending on the angle and phase parameters.     

CP asymmetries in chargino production and decay: the three-body decay case

We study CP violation in chargino production and decay in the minimal supersymmetric standard model (MSSM) with complex parameters at an e⁺e^- linear collider with longitudinally polarised beams. We investigate CP-sensitive asymmetries by means of triple product correlations and study their dependence on the complex parameters M₁ and μ. We give numerical predictions for the asymmetries and their measurability at the future International Linear Collider. Our results show that the CP asymmetries can be measured in a large region of the MSSM parameter space.     

To the application of the emission Mössbauer and positron annihilation spectroscopies for detection of carcinogens

Being the main cause of cancer, almost all chemical carcinogens are strong electrophiles, that is, they have a high affinity for the electron. We have shown that positron annihilation lifetime spectroscopy (PALS) is able to detect chemical carcinogens by their inhibition of positronium (Ps) formation in liquid media. Electrophilic carcinogens intercept thermalized track electrons, which are precursors of Ps, and as a result, when they are present Ps atom does not practically form. Available biophysical data seemingly indicate that frozen solutions model better an intracellular medium than the liquid ones. So it is reasonable to use emission Mössbauer spectroscopy (EMS) to detect chemical carcinogens, measuring the yield of ⁵⁷Fe²⁺ions formed in reactions of Auger electrons and other secondary electrons they produced with ⁵⁷Fe³⁺. These reactions are similar to the Ps formation process in the terminal part the positron track: e⁺+ e^? =>Ps. So EMS and PALS are complementary methods for detection of carcinogenic compounds.     

B-decay CP-asymmetries in SUSY with a U(2)3 flavour symmetry

We study CP asymmetries in rare B decays within supersymmetry with a U(2)³ flavour symmetry, motivated by the SUSY flavour and CP problems, the hierarchies in the Yukawa couplings and the absence so far of any direct evidence for SUSY. Even in the absence of flavour-blind phases, we find potentially sizable CP violating contributions to b→s decay amplitudes. The effects in the mixing-induced CP asymmetries in B→ϕK _S and B→η′K _S , angular CP asymmetries in B→K ^∗ μ ⁺ μ ⁻ and the direct CP asymmetry in B→X _s γ can be in the region to be probed by LHCb and next generation B factories. At the same time, these effects in B decays are compatible with CP violating contributions to meson mixing, including a non-standard B _s mixing phase hinted by current tensions in the CKM fit mostly between S_yKS, e_KS_{\psi K_{S}}, \epsilon_{K} and DM_Bs/DM_Bd\Delta M_{B_{s}}/\Delta M_{B_{d}}.     

Positronium decay and formation in paraffin wax from polarized and unpolarized positrons

Summary Ps formation and decay in heterogeneousn-alkane samples (paraffin waxes) have been studied both in the solid and in the liquid phase; then, in the solid phase, the positron's residual degree of polarization was measured at the instant of Ps formation. Differently from what is already known in homogeneousn-alkane samples, Ps shows, many degrees below the melting point, a mean lifetime longer than that typical of the liquid phase; furthermore, the mean lifetime's values pertaining to the transition between solid and liquid do not show a sharp variation across the melting temperature but gradually decrease over a range of temperatures of several degrees. Positronium decay in static magnetic fields indicates that o-Ps magnetic quenching in liquid phase is regular, and corresponds to a contact density value α=|ψ(0)|²/|ψ(0)|_vac ²=0.79±0.07; instead, in the solid phase, o-Ps magnetic quenching shows anomalous behaviour for fields weaker than 7kG. Positrons' residual polarization measurements do not reveal the presence of depolarization effects during the whole slowing-down process until Ps is formed.     

An experimental study of cross polarization from1H to27Al in crystalline and amorphous materials

The conditions for successful¹H?²⁷Al cross polarization experiments have been investigated. It was found that boehmite was a good material for setting up the Hartmann-Hahn match condition, and both tetrahedral and octahedral aluminium was observed in a variety of environments. The contact time dependence of the CP signal was studied for several samples and simulations showed thatT _IS could be estimated and hence information on mean¹H?²⁷Al distances in glasses deduced. CP signals could be obtained even ifT _1? ^Al is much less thanT _IS, contrary to some previous suggestions. MAS reduces both the size of the CP signal and the optimum contact time and to maintain signal strength spinning should be as slow as possible.     

Review of the KL → μ+μ− puzzle

It is recalled that the conventional mechanisms for weak and electromagnetic interactions and for observed particles lead via, unitarity and CPT, to a predicted value for the branching ratio of K_L → μ⁺μ^? in contradiction with the experimental upper limit. We review the models suggested as a solution to this puzzle which introduce new particles and/or new interactions; the models which preserve CP invariance appear unattractive or seem dubious from the experimental point of view; the models which incorporate large CP violations, predict an anomalously large value for the (K_S → μ⁺μ^?)-branching ratio which requires experimental confirmation.     

A further study of CP asymmetries in pure Penguin-inducedB u ± decays

We make a further study of CP asymmetries in the pure penguin-induced decay modesB _u ^? →K ^(*)0+K ^(*)? and $B_u^ - \to \bar K^{(*)0} + (\pi ^ - ,\rho ^ - ,a_1^ - )$ by using the twoloop renormalization-group-improved effective Hamiltonian and factorization approximation. Different from the previous results obtained without QCD corrections, the CP asymmetries in each of the two groups are enhanced and classified with their respective factorization coefficients. A sum over the pure penguin modes of each group is proposed to obtain an effective branching ratio and aweighted-mean signal of CP violation, which should be statistically significant for experimental observation.     

Complex-Scaling Calculations for Doubly Excited Resonances in Ps? Interacting with Screened Coulomb (Yukawa) Potentials

We have investigated the effect of screened Coulomb potentials on the high-lying doubly excited resonance states of the positronium negative ion in the framework of complex-scaling method. Highly correlated wave functions in Hylleraas coordinates are used. The resonance parameters below the Ps (2s²S) and Ps (3s²S) thresholds, for various screening parameters, are reported.     

Decay of the positronium molecule into a positronium atom and photons

Decays of the positronium molecule Ps₂ into para- or orthopositronium Ps in the ground state and photons are investigated. The differential probabilities of the decays are determined. The total probabilitiesw _2γ ^(Ps2) andw _3γ ^(Ps2) of Ps₂ annihilation with the production of two and three photons and positronium are calculated to be $$w_{2\gamma }^{(P_{S_2 } )} = 1.6 \cdot 10^{10} \sec ^{ - 1} ,w_{3\gamma }^{(P_{S_2 } )} = 0.43 \cdot 10^8 \sec ^{ - 1} $$ . The curve of the angular correlation of the γ rays on the decay of Ps₂ into two photons and parapositronium is studied. The width of this curve is Δ¦P¦=0.128 a.u. (¦P¦ is the total photon momentum), which corresponds to a deviation of the emission angle of the γ rays from π: θ ? 0.934 mrad. The maximum in the distribution of the photons with respect to the momenta ¦P¦ in the center of mass of the annihilating pair is attained at ¦P¦=0.175 a.u. The calculations were made on an M-222 computer, and their accuracy is determined by the choice of the wave function of the positronium molecule and the accuracy in the computer calculation of the integrals.     

New physics hints in B decays and collider outlook

There are currently two hints for new physics involving CP violation in b → s transitions: ΔS ≡ S _f − S _J ^ϕK ≠ 0, and difference in direct CP asymmetry ΔA _Kπ ≡ A _K+π ⁰ − A _K+π ⁻ ≠ 0. We explore the two scenarios with a large and unique new CP phase in b ↔ s transitions. Motivated by ΔS ≠ 0, we update on the right-handed strange-beauty squark sb _1R at TeV scale. Motivated by ΔA _Kπ ≠ 0, we explore sequential fourth generation t′ and b′ quarks. Both scenarios can survive constraints such as SM level b → sγ, sll and B _s mixing, and predict sizable CP violation in B _s mixing. The fourth generation picture predicts sizable K _L → π ⁰ vv. Direct search for sb _R, b′ and t′ at hadronic colliders, such as Tevatron Run II and LHC, can complement further CP violation studies at these machines, as well as at the future Super B factory.     

The vibration-rotation spectrum of methinophosphide: l-Type doubling, l-type resonance and the ν2, 2ν2, and 3ν2 bands of H12CP; The ν1 and ν2 bands of H13CP

The vibration-rotation bands ν₂, 2ν₂, and several “hot” bands of H¹²CP have been recorded and assigned. The states with v₂ = 2, perturbed by l-type resonance and l-type doubling effects have been analyzed on the basis of the existing theory. The energy difference between the 02²0 and the 02⁰0 states was found to be 17.5095 (19) cm^?1. Because of insufficient data, the states with v₂ = 3 could not be corrected for l-type resonance interaction and therefore only an effective l-type doubling constant was obtained. The ν₁ and ν₂ bands of the H¹³CP isotopic molecule (present at natural concentration) were also identified and their spectroscopic constants obtained. The value of I_e for H¹²CP is found to be 25.18793 (26) amu Ų.