Neutrino-pair bremsstrahlung and the number of lepton generations

Neutrino pair creation in bremsstrahlung processes of the type \(l \to l{\text{ }}v{\text{ }}\bar v\) contains vital information on the number of lepton generations, and is catalyzed by the coherent nuclear Coulomb effect or other forms of intense fields. Of particular interest is the ratio \(R_{v\bar v} = \sigma [1\mathop \to \limits_A l(v\bar v)]/\sigma [1\mathop \to \limits_A l'(v\bar v)]\) (wherel, l′ are distinct charged leptons). It is sensitive to the number of neurino types and their couplings in the same way that the ratio \(R_{q\bar q} = \sigma [e^ + e^ - \to {\text{hadrons}}]/\sigma [e^ + e^ - \to \mu ^ + \mu ^ - ]\) is to those of quarks. In the Weinberg-Salam model withN lepton generations, the ratio \(R_{v\bar v}\) is approximately given by \([(N + 4) + 4(1 - 4\sin ^2 \theta _W )]/8\) .     

Is there any “LSND anomaly”?

The LSND Collaboration reported a 3.8σ excess of $\bar v_e $ over background. In this experiment 800MeV protons were dumped into a water target. LSND experimentalists interpreted this excess as evidence for $\bar v_\mu \to \bar v_e $ oscillations, which led to the hypothesis of the existence of ‘sterile’ neutrinos. LSND’s claim was not confirmed by the MiniBooNE Collaboration, so the origins of the LSND result were never clarified. The data from the HARP-CDP group on pion production by 800 MeV protons are used in an independent calculation of LSND’s $\bar v_e $ background. The pion production by neutrons which had been ignored in LSND’s calculations is also taken into account. We conclude that LSND’s claim of a 3.8 σ excess cannot be upheld.     

Production Reaction of {{\bf \bar{K}}{NN}-{\bf \pi}{YN}} Resonance from Faddeev Equations

As a first step toward clarifying whether the strange dibaryon resonances in the ${\bar{K}NN-\pi YN}$ system can emerge with a physical significance in the nuclear-reaction observables, we compute the break-up probability of ${Y_K + N \to \pi +\Sigma + N}$ at real scattering energies by solving ${\bar{K}NN-\pi YN}$ coupled-channel Alt–Grassberger–Sandhas equations. We examine how the signature of the dibaryon resonance shows up in the probability, and also discuss the possibility for a use of strange dibaryon production reactions to distinguish two-body-interaction models with Λ(1405).     

Production of π0 mesons and charged hadrons in\bar v neon and ν neon charged current interactions

The average multiplicities of charged hadrons and of π⁺, π^? and π⁰ mesons, produced in \(\bar v\) Ne and νNe charged current interactions in the forward and backward hemispheres of theW ^±-nucleon center of mass system, are studied with data from BEBC. The dependence of the multiplicities on the hadronic mass (W) and on the laboratory rapidity (y _Lab) and the energy fraction (z) of the pion is also investigated. Special care is taken to determine the π⁰ multiplicity accurately. The ratio of average π multiplicities \(\frac{{2\left\langle {n_{\pi ^O } } \right\rangle }}{{[\left\langle {n_{\pi ^ + } } \right\rangle + \left\langle {n_{\pi ^ - } } \right\rangle ]}}\) is consistent with 1. In the backward hemisphere \(\left\langle {n_{\pi ^O } } \right\rangle \) is positively correlated with the charged multiplicity. This correlation, as well as differences in multiplicities between \(\mathop v\limits^{( - )} \) and \(\mathop v\limits^{( - )} \) , \(\mathop v\limits^{( - )} \) scattering, is attributed to reinteractions inside the neon nucleus of the hadrons produced in the initial \(\mathop v\limits^{( - )} \) interaction.     

Physics beyond the Standard Model through b → s μ ?+? μ ? transition

A comprehensive study of the impact of new-physics operators with different Lorentz structures on decays involving the b ?? s ?? ^?+? ?? ^? transition is performed. The effects of new vector?Caxial vector (VA), scalar?Cpseudoscalar (SP) and tensor (T) interactions on the differential branching ratios, forward?Cbackward asymmetries (A _FB??s), and direct CP asymmetries of ${\bar B}_{\rm s}^0 \to \mu^+ \mu^-$ , ${\bar B}_{\rm d}^0 \to$ $ X_{\rm s} \mu^+ \mu^-$ , ${\bar B}_{\rm s}^0 \to \mu^+ \mu^- \gamma$ , ${\bar B}_{\rm d}^0 \to {\bar K} \mu^+ \mu^-$ , and ${\bar B}_{\rm d}^0\to {\bar{K}^*} \mu^+ \mu^-$ are examined. In ${\bar B}_{\rm d}^0\to {\bar{K}^*} \mu^+ \mu^-$ , we also explore the longitudinal polarization fraction f _L and the angular asymmetries $A_{\rm T}^{(2)}$ and A _LT, the direct CP asymmetries in them, as well as the triple-product CP asymmetries $A_{\rm T}^{\rm (im)}$ and $A^{\rm (im)}_{\rm LT}$ . While the new VA operators can significantly enhance most of the observables beyond the Standard Model predictions, the SP and T operators can do this only for A _FB in ${\bar B}_{\rm d}^0 \to {\bar K} \mu^+ \mu^-$ .     

Chiral symmetry breaking in the colour dielectric model

Approximating the long-distance gluon dynamics ofSU(3)_colour by colour-dielectric block-spin variables, we obtain an effective QCD theory of a scalar colour-dielectric field and a massive colour-bleached gluon field coupled to light quarks. The massive vector field produces a strong attraction betweenq \(\bar q\) pairs, which leads toq \(\bar q\) condensation when the colour-dielectric field becomes small. We calculate \(\left\langle {\bar \psi \psi } \right\rangle\) and the pion decay constantf _n as a function of the dielectric field expectation value, by evaluating the fermion determinant in a derivative expansion, and integrating out the bosonic variables. We find that the effective quark-gluon coupling,α _s ^eff , including quark effects, is large on the surface of bags, where \(\left\langle {\bar \psi \psi } \right\rangle\) ±0, but decreases inside hadronic bags, where | \(\left\langle {\bar \psi \psi } \right\rangle\) | is decreasing.     

Isgur-Wise functions from the MIT bag model

The Isgur-Wise functions for the ground state to ground state semileptonic decays involvingb→c transitions are calculated from the (modified) MIT bag model. It is checked that the results for the decays \(\bar B \to Dl\bar v\) and \(\bar B \to D^* l\bar v\) agree well with experiment. Predictions for the decays \(\Lambda _b \to \Lambda _c l\bar v,\bar B_s \to D_s^* l\bar v\) and \(\bar B_s \to D_s^* l\bar v\) are given and discussed.     

Light quark masses in quantum chromodynamics and chiral symmetry breaking

We derive model independent lower bounds for the sums of effective quark masses \(\bar m_u + \bar m_d \) and \(\bar m_u + \bar m_s \) . The bounds follow from the combination of the spectral representation properties of the hadronic axial currents two-point functions and their behavior in the deep euclidean region (known from a perturbative QCD calculation to two loops and the leading non-perturbative contribution). The bounds incorporate PCAC in the Nambu-Goldstone version. If we define the invariant masses \(\hat m\) by $$\bar m_i = \hat m_i \left( {{{\frac{1}{2}\log Q^2 } \mathord{\left/ {\vphantom {{\frac{1}{2}\log Q^2 } {\Lambda ^2 }}} \right. \kern-\nulldelimiterspace} {\Lambda ^2 }}} \right)^{{{\gamma _1 } \mathord{\left/ {\vphantom {{\gamma _1 } {\beta _1 }}} \right. \kern-\nulldelimiterspace} {\beta _1 }}} $$ and <F ²> is the vacuum expectation value of $$F^2 = \Sigma _a F_{(a)}^{\mu v} F_{\mu v(a)} $$ , we find, e.g., $$\hat m_u + \hat m_d \geqq \sqrt {\frac{{2\pi }}{3} \cdot \frac{{8f_\pi m_\pi ^2 }}{{3\left\langle {\alpha _s F^2 } \right\rangle ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} }}} $$ ; with the value <α _u F ²?0.04GeV⁴, recently suggested by various analysis, this gives $$\hat m_u + \hat m_d \geqq 35MeV$$ . The corresponding bounds on \(\bar m_u + \bar m_s \) are obtained replacingm _π ² f _π bym _K ² f _K . The PCAC relation can be inverted, and we get upper bounds on the spontaneous masses, \(\hat \mu \) : $$\hat \mu \leqq 170MeV$$ where \(\hat \mu \) is defined by $$\left\langle {\bar \psi \psi } \right\rangle \left( {Q^2 } \right) = \left( {{{\frac{1}{2}\log Q^2 } \mathord{\left/ {\vphantom {{\frac{1}{2}\log Q^2 } {\Lambda ^2 }}} \right. \kern-\nulldelimiterspace} {\Lambda ^2 }}} \right)^d \hat \mu ^3 ,d = {{12} \mathord{\left/ {\vphantom {{12} {\left( {33 - 2n_f } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {33 - 2n_f } \right)}}$$ .     

Effects of final-state interaction and screening on strange- and heavy-quark production

Final-state interaction and screening have a great influence on $q\bar q$ production cross sections, which are important quantities in many problems in quark-gluon plasma physics. They lead to an enhancement of the cross section for a $q\bar q$ color-singlet state and a suppression for a color-octet state. The effects are large near the production threshold. The presence of screening gives rise to resonances for $q\bar q$ production just above the threshold at specific plasma temperatures. These resonances, especially $c\bar c$ and $b\bar b$ resonances, may be utilized to search for the quark-gluon plasma by studying the temperature dependence of heavy-quark pair production just above the threshold.     

Topological vertex,string amplitudes and spectral functions of hyperbolic geometry

We study radiative corrections to massless quantum electrodynamics modified by two dimension-five LV interactions $\bar{\Psi } \gamma ^{\mu } b'^{\nu } F_{\mu \nu }\Psi $ and $\bar{\Psi }\gamma ^{\mu }b^{\nu } \tilde{F}_{\mu \nu } \Psi $ in the framework of effective field theories. All divergent one-particle-irreducible Feynman diagrams are calculated at one-loop order and several related issues are discussed. It is found that massless quantum electrodynamics modified by the interaction $\bar{\Psi } \gamma ^{\mu } b'^{\nu } F_{\mu \nu }\Psi $ alone is one-loop renormalizable and the result can be understood on the grounds of symmetry. In this context the one-loop Lorentz-violating beta function is derived and the corresponding running coefficients are obtained.     

On strange quark scalar condensate in the nucleon

A well known difficulty with a large value of the σ term in πN scattering is analysed from positions of the QCD sum rules approach. The matrix element \(\left\langle {p\left| {\bar ss} \right|p} \right\rangle\) is related to flavour singlet correlation function of two quark condensates at zero momentum. The splittings \(\left\langle {p\left| {\bar uu - \bar ss} \right|p} \right\rangle\) and \(\left\langle {p\left| {\bar dd - \bar ss} \right|p} \right\rangle\) are calculated and turn to be in agreement withSU ₃ relations.     

Antihydrogen (hydrogen) atom formation

In this paper we show how the ATHENA data samples on the antihydrogen ( ${\bar{\rm H}}$ ) formation in very different conditions provide useful information on the two different possible mechanisms: the 3-body reaction ( $\bar{p}+{e^+}+{e^+}\rightarrow {\bar{\rm H}}+ e^+$ ) and the 2-body reaction ( $\bar{p}+{\rm e^+}\rightarrow {\bar{\rm H}}+{h\nu}$ ).     

\bar pp-Annihilation processes in the tree approximation of SU(3) chiral effective theory

The $\bar pp$ -annihilation reactions $\bar pp \to \eta \eta \eta$ and $\bar pp \to \eta {\rm K}\bar {\rm K}$ at rest are considered in the tree approximation in the framework of SU(3) chiral effective theory at leading order. The calculated branchings are compared with the data. The results for neutral (????, $\eta {\rm K}^0 \bar {\rm K}^0$ ) and charged (??K ⁺ K ^?) channels are essentially different.     

N\bar N annihilation at rest into πππ andK\bar K\pi in the3 P 0 model and selection rules on the πρ,K\bar K* and\bar KK* production

\(N\bar N\) annihilation into three pseudoscalar mesons especially πππ and \(K\bar K\pi \) are studied in the quark pair creation model or the³ P ₀ model in which two \(q\bar q\) pairs are annihilated and two \(q\bar q\) pairs are created with quantum numbers of the vacuum or³ P ₀. The correlations of two pions to form ?,f ₂ and the resonance AX(1565) which is recently found by the ASTERIX group are taken into account. A proper treatment of the symmetry among the three pions in the final state shows that the \({}^{31}S_0 p\bar p\) annihilation into ?π is suppressed in agreement with the experiment. We calculate the cosθ distribution or the distribution of the Dalitz plot as the function of the angle between the direction of emission of one decay pion in the resonance centre of mass and the line of flight of the resonance. The interferences of π⁺ρ⁺, π^?ρ⁺ and π⁰ρ⁰ in the isospin 0 channels and π^±ρ^? and π⁰ f ₂ in the isospin 1 channel reproduce the peaks. The cos θ distribution for the P-wave \(p\bar p\) annihilation into πAX depends strongly on the size of the pion since the amplitude interfers with the π^±ρ^? amplitude which is sensitive to the size of the pion. The same model qualitatively explains the \(p\bar p\) annihilation into \(K\bar K\pi \) in whichK or \(\bar K\) and π are correlated to formK* \(\bar K\) or \(\bar K\) *K final states. We can qualitatively reproduce different patterns of the cos θ distribution for theK ^*+ andK ^*0.     

Measurement of the Λ→p μ− ¯v branching ratio

A sample of 1.2× 10⁶ Λ-hyperons was analyzed in order to detect the rare decay mode: Λ →pμ^?¯v. The Λ-hyperons were produced by stoppingK ^?-mesons in the 81 cm Saclay hydrogen bubble chamber at the CERN PS. We obtained for the branching ratio: $$\frac{{\Gamma {\text{(}}\Lambda \to p\mu ^ - \bar \nu )}}{{\Gamma {\text{(}}\Lambda \to {\text{all)}}}} = (1.4 \pm 0.5) \times 10^{ - 4} ,$$ based on 20 events, of which 6 have to be attributed to the background from the reaction $$\Lambda \to p\pi ^ - , \pi ^ - \to \mu ^ - \bar v.$$ The background was determined by a Monte Carlo calculation.     

Charm Production in Antiproton-Proton Annihilation

We study the production of charmed mesons (D) and baryons (?? _c ) in antiproton-proton ${(\bar{p}p)}$ annihilation close to their respective production thresholds. The elementary charm production process is described by either baryon/meson exchange or by quark/gluon dynamics. Effects of the interactions in the initial and final states are taken into account rigorously. The calculations are performed in close analogy to our earlier study on ${\bar{p}p \to \bar{\Lambda} \Lambda}$ and ${\bar{p} p \to \bar{K} K}$ by connecting the processes via SU(4) flavor symmetry. Our predictions for the ${\bar{\Lambda}_c \Lambda_c}$ production cross section are in the order of 1 to 7 mb, i.e. a factor of around 10?C70 smaller than the corresponding cross sections for ${\bar{\Lambda} \Lambda}$ However, they are 100 to 1000 times larger than predictions of other model calculations in the literature. On the other hand, the resulting cross sections for ${\bar{D} D}$ production are found to be in the order of 10^?2 ?C 10^?1 ??b and they turned out to be comparable to those obtained in other studies.     

Jeans instability in superfluids

Recent numerical studies of the coupled Einstein–Klein–Gordon system in a cavity have provided compelling evidence that confined scalar fields generically collapse to form black holes. Motivated by this intriguing discovery, we here use analytical tools in order to study the characteristic resonance spectra of the confined fields. These discrete resonant frequencies are expected to dominate the late-time dynamics of the coupled black-hole-field-cage system. We consider caged Reissner–Nordström black holes whose confining mirrors are placed in the near-horizon region \(x_{\text {m}}\equiv (r_{\text {m}}-r_+)/r_+\ll \tau \equiv (r_+-r_-)/r_+\) (here \(r_{\text {m}}\) is the radius of the confining mirror and \(r_{\pm }\) are the radii of the black-hole horizons). We obtain a simple analytical expression for the fundamental quasinormal resonances of the coupled black-hole-field-cage system: \(\omega _n=-i2\pi T_{\text {BH}} \cdot n\left[ 1+O(x^n_{\text {m}}/\tau ^n)\right] \) , where \(T_{\text {BH}}\) is the temperature of the caged black hole and \(n=1,2,3,...\) is the resonance parameter.     

About Maxwell’s equations on fractal subsets of ℝ3

In this paper we have generalized $F^{\bar \xi }$ -calculus for fractals embedding in ?³. $F^{\bar \xi }$ -calculus is a fractional local derivative on fractals. It is an algorithm which may be used for computer programs and is more applicable than using measure theory. In this Calculus staircase functions for fractals has important role. $F^{\bar \xi }$ -fractional differential form is introduced such that it can help us to derive the physical equation. Furthermore, using the $F^{\bar \xi }$ -fractional differential form of Maxwell’s equations on fractals has been suggested.     

The process\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma as an alternative to\pi ^0 \to v\bar v

The process \(\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma \) is investigated as an alternative to \(\pi ^0 \to v\bar v\) . It is shown that the experimental bound on the branching fraction for missing energy (in the form of \(\lambda _\gamma \bar \lambda _\gamma \) and/or \(v\bar v\) ) may be understood in terms of \(\pi ^0 \to \lambda _\gamma \bar \lambda _\gamma \) for the kinematically allowed photino mass, if the squark mass is >8 GeV.