Effects of anomalousZ 0 decays on neutrino counting near theZ 0 peak

We study the implications of the anomalousZ ⁰ decays on neutrino counting ine ⁺ e ^? collisions. The \(Z^0 \to l\bar l\gamma \) vertex is parametrized by an effective Lagrangian,L _eff, satisfyingU(1)_em gauge invariance, CP and chirality conservation. The parameters ofL _eff are constrained by the ratio \(\Gamma (Z \to l\bar l\gamma )/\Gamma (Z \to l\bar l)\) , Bhabba scattering, and low energyv _µ e scattering data. We find that the effect on neutrino counting can be significant but depends on the magnitude and relative signs of the parameters inL _eff. We also find that accurate measurements of the cross-section \(\sigma (e^ + e^ - \to v\bar v\gamma )\) at theZ ⁰ peak can be used as a sensitive test for new physics.     

Scalar electron and zino production on and beyond theZ resonance ine + e − annihilation

We study the production of scalar electrons ine ⁺ e ^? collisions on and above theZ resonance. By calculating the cross-section for \(e^ + e^ - \to e^ + e^ - \tilde \gamma \tilde \gamma \) we show that scalar electrons with mass above the beam energies \((\sqrt s /2)\) can be identified. In particular if a zino with mass \(m_{\tilde z}< \sqrt s - m_{\tilde \gamma } \) exists then zino production and decay can give a contribution which dominates the γ exchange contributions. We present final state distributions.     

Remarks about the counting of\bar vv generations using thee + e − →γZ 0 process

In the present note we further explore the possibility of measuring the number of \(\bar vv\) generations by means of \(Z^0 \to \bar vv\) decays. We investigate in particular the case where the radiative transitionse ⁺ e ^? →γZ ⁰ are studied on theZ ⁰ resonance itself. The various background reactions are discussed as well as the statistical significance that can be obtained for an additional \(\bar vv\) generation.     

Baryon pairs production ine + e − annihilation at\sqrt s = 2.4 GeV

Search for baryon pairs production ine ⁺ e ^? annihilation at \(\sqrt s = 2386 MeV\) is reported. The data relate to a luminosity of 161 nb^?1 collected by the DM2 experiment at DCI, the Orsay colliding ring. First measurements of directe ⁺ e ^? annihilation into \(\Lambda \bar \Lambda \) and ofe ⁺ e ^?→ \(p\bar p\) at this energy are presented. First observation of a goode ⁺ e ^?→ \(n\bar n\) candidate is reported and upper limits are given fore ⁺ e ^?→ \(n\bar n, \Lambda \bar \sum ^0 + c.c.\) and \(\Sigma ^0 \bar \Sigma ^0 \) .     

Weak contributions to angular asymmetries ine + e − annihilation

We study the energy and polarization dependence of angular asymmetries ine ^? e ⁺→ψ,Z ⁰→f \(\bar f\) (f=lepton or quark). Through the fragmentation of the quarks the corresponding asymmetries are obtained for the jet axis ine ^? e ⁺→ψ,Z ⁰→(Σq \(\bar q\) )→2 jets, and for inclusively produced hadronsh(h=π⁺,K ⁺ and π⁺ +K ⁺) ine ^? e ⁺→ψ,Z ⁰→(Σq \(\bar q\) )→(h+X)_2jet. In the Weinberg-Salam model these asymmetries come out big enough to show up already at upper PETRA and PEP energies.     

Recurrence of random walks in the Ising spins

Consider the 1/2-Ising model inZ ². Let σ _j be the spin at the site (j, 0)∈Z ² (j=0, ±1, ±2, ...). Let \(\{ X_n \} _{n = 0}^{ + \infty } \) be a random walk with the random transition probabilities such that $$P(X_{n + 1} = j \pm 1|X_n = j) = p_j^ \pm \equiv 1/2 \pm v(\sigma _j - \mu )/2$$ We show a case whereE[p _j ⁺ ≧E[p _j ^? ], but \(\mathop {\lim }\limits_{n \to \infty } X_n = - \infty \) is recurrent a.s.     

Anomalous magnetic moment of theW-bosons and non-standardZ 0 W + W − coupling in polarizede − e + collisions

We study quantitatively the reactions \(e^ + e^ - \to W^ + e\bar \nu _e \) ,e _R ^? e ⁺ and the rare decay \(Z^0 \to W^ \pm l^ \mp \mathop {\nu _e }\limits^{( - )} \) forl=e, μ and τ, as a test for anomalous γW ⁺ W ^? andZ ⁰ W ⁺ W ^? structure. If κ denotes the anomalous magnetic moment of theW-boson and ω its anomalous coupling to theZ ⁰, values of |ω|>2.5 and |κ|>1.5 can be ruled out at LEP and SLC rather easily. This will put constraints on composite model building.     

Jet-like distributions from the weak decay of heavy quarks

We consider the production and weak decay of a pair of heavy quarks (mesons) ine ⁺ e ^? experiments and study their effect on the various jet distributions. The relative magnitudes of the two-quark-jet and three-quark-jet final states, in the decay of a heavy quark are estimated in the framework of an SU(2) _L ×U(1) model. We find that the three quark configuration dominates over the two quark configuration. For the quark jets resulting from the weak decay of the heavy quarks, we calculate the jet distributions in Sphericity, Spherocity and Thrust for the process \(e^ + e^ - \to Q\bar Q \to 6\) quarks. These distributions are compared with the corresponding quantities from the non-perturbative process \(e^ + e^ - \to q\bar q\) and the QCD process \(e^ + e^ - \to q\bar qg\) . We find that the weak decay of heavy quarks is the dominant mechanism for jet broadening ine ⁺ e ^? experiments, in the intermediate energy region relevant for PETRA and PEP.     

The final statesl ± K ± K ± X in jets as signatures ofB_s^0 - \bar B_s^0 mixings

Significant mixing is expected between the neutral bottom mesons \(B_s^0 - \bar B_s^0 \) in the standard model of weak interactions. We propose measurements of the processes \(\left\{ {\begin{array}{*{20}c} {e^ + e^ - } \\ {p\bar p} \\ \end{array} } \right\} \to \begin{array}{*{20}c} {b\bar b} \\ {} \\ \end{array} \to l^ + K^ - K^ - X\) as a measure of such mixing. Rates are presented for energetic bottom quark jets, produced ine ⁺ e ^? annihilation.     

e^ + e^ - \to b\bar bW^ + W^ - events at the next linear collider: colour structure of top signal and irreducible backgroundevents at the next linear collider: colour structure of top signal and irreducible background

We examine the colour structure and charged particle yield for both the $t\bar t$ signal and the irreducible background processes contributing to $e^ + e^ - \to b\bar bW^ + W^ - $ production close to the $t\bar t$ threshold. The charged particle multiplicity for the various components of the cross section is computed as a function of several kinematic variables. Our study may have important implications for recently proposed studies of interconnection phenomena in $t\bar t$ production at high-energye ⁺ e ^? colliders.     

Quark-diagram estimates ofCP violation in two-body baryonicB_d^0 - \bar B_d^0 decays

CP violation in partial-decay-rate asymmetries are examined for some two-body baryonic decays of \(B_d^0 - \bar B_d^0 \) system. We discuss two feasible experimental circumstances: the symmetrice ⁺ e ^? collisions (i) on theZ ⁰ resonance to produce incoherent \(B_d^0 \bar B_d^0 \) states, and (ii) just above the ?(4S) resonance to produceC=even \(B_d^0 \bar B_d^0 \) states. Using the quark-diagram scheme, we estimate the branching ratios of those decays, and the numbers ofb \(\bar b\) pairs needed for testing theCP-violating effects for 3σ signature. We find that the promising channels may beB _d ⁰ , \(\bar B_d^0 \to p\bar p\) , \(\Delta ^ + \bar \Delta ^ - \) , \(p\bar \Delta ^ - \) , \(\Delta ^ + \bar p\) , \(n\bar n\) , \(\Delta ^0 \bar \Delta ^0 \) , \(n\bar \Delta ^0 \) , \(\Delta ^0 \bar n\) , \(\Sigma _c^ + \bar \Sigma _c^ - \) , \(\Lambda _c^ + \bar \Lambda _c^ - \) , \(\Sigma _c^ + \bar \Lambda _c^ - \) , \(\Lambda _c^ + \bar \Sigma _c^ - \) , \(\Sigma _c^0 \bar \Sigma _c^0 \) , \(\Xi _c^0 \bar \Xi _c^0 \) , which should be interesting for experimental observation.     

Polarization density matrix forZ decay intoWff' with generalZWW couplings

We give the polarization density matrix ofZ andW for the decay processZ ⁰→Wff' with generalZWW couplings. The matrix elements are expressed in terms of kinematical invariants so that they can be readily used in \(p\bar p \to Z^0 W\) as well. Using these formulas, we analyze the possibilities of probing theZWW couplings through the decay of polarizedZ ⁰.     

Z c (4025) as the hadronic molecule with hidden charm

We have studied the loosely bound $D^{*}\bar{D}^{*}$ system. Our results indicate that the recently observed charged charmonium-like structure Z _c (4025) can be an ideal $D^{*}\bar{D}^{*}$ molecular state. We have also investigated its pionic, dipionic, and radiative decays. We stress that both the scalar isovector molecular partner Z _c0 and three isoscalar partners ${\tilde{Z}}_{c0,c1,c2}$ should also exist if Z _c (4025) is a $D^{*}\bar{D}^{*}$ molecular state in the framework of the one-pion-exchange model. Z _c0 can be searched for in the channel e ⁺ e ^?→Y→Z _c0(4025)(ππ)_P-wave where Y can be Y(4260) or any other excited 1^?? charmonium or charmonium-like states such as Y(4360), Y(4660), etc. The isoscalar $D^{*}\bar{D}^{*}$ molecular states ${\tilde{Z}}_{c0,c2}$ with 0⁺(0⁺⁺) and 0⁺(2⁺⁺) can be searched for in the three pion decay channel $e^{+}e^{-}\to Y \to {\tilde{Z}}_{c0,c2} (3\pi)^{I=0}_{\text{P-wave}}$ . The isoscalar molecular state ${\tilde{Z}}_{c1}$ with 0^?(1^+?) can be searched for in the channel ${\tilde{Z}}_{c1}\eta$ . Experimental discovery of these partner states will firmly establish the molecular picture.     

Duality ine + e − annihilation

With the help of a relativistic generalization of the formula for the leptonic width of quarkonium in the semiclassical approximation it is shown that for any confinement potential nonsingular at the origin the sum of total cross sections for the production of the heavy quarkonium states \((Q\bar Q)_n\) with masses \(M_n \leqq \sqrt s\) ine ⁺ e ^?-annihilation is equal to the cross section at givens for the production of the free quark-antiquark pair \(Q\bar Q\) . We obtain also a family of dual sum rules for quarkonium which are in agreement with the available experimental data on charmonium and beautionium within experimental errors.     

Gauge vector boson pair production at\bar p p collider energies

Within the standardSU(2)×U(1) model differential cross sections and angular distributions of all polarization states are studied for all channels of gauge vector boson pairs accessible in hadron hadron collisions,W ⁺ W ^?,Z ⁰ Z ⁰,Zγ,ZW, γW. The zero in the unpolarized angular distribution ofq \(\bar q\) →Wγ reported theoretically by Mikaelian et al. [1] is confirmed. The origin of this zero is studied which was discovered by Brown, Mikaelian, Samuel, and Shadev. None of the other channels exhibits a zero in the unpolarized angular distribution, but strong minima at cosΘ=0 are predicted for \(q_i \bar q_j \to Z\gamma \) and \(q_i \bar q_j \to ZW^ + \) . These are of different origin than the Mikaelian zero. Simple structure functions suggest that these minima are seen inp \(\bar p\) collisions.     

Localization in the ground state of a disordered array of quantum rotators

We consider the zero-temperature behavior of a disordered array of quantum rotators given by the finite-volume Hamiltonian: $$H_\Lambda = - \mathop \Sigma \limits_{x \in \Lambda } \frac{{h(x)}}{2}\frac{{\partial ^2 }}{{\partial \varphi (x)^2 }} - J\mathop \Sigma \limits_{\left\langle {x,y} \right\rangle \in \Lambda } \cos (\varphi (x) - \varphi (y))$$ , wherex,y∈Z ^d , 〈,〉 denotes nearest neighbors inZ ^d ;J>0 andh={h(x)>0,x∈Z ^d } are independent identically distributed random variables with common distributiondμ(h), satisfying ∫h ^?δ dμ(h)<∞ for some δ>0. We prove that for anym>0 it is possible to chooseJ(m) sufficiently small such that, if 0<J<J(m), for almost every choice ofh and everyx∈Z ^d the ground state correlation function satisfies $$\left\langle {\cos (\varphi (x) - \varphi (y))} \right\rangle \leqq C_{x,h,J} e^{ - m\left| {x - y} \right|} $$ for ally∈Z ^d withC _x,h,J <∞.     

Production of singleW bosons ine + e − ande − p collisions

The production ofW bosons in electronpositron colliding beams below theW ⁺ W ^? threshold is discussed. The corresponding reactions \(e^ + e^ - \to l^ \pm W^ \mp \mathop {\nu _l }\limits^{( - )} \) yield total cross-sections of the order of 10^?37 cm² (forl=e) and 10^?38 cm² (forl=μ). The total cross-sections as well as the angular and energy distributions of theW boson in \(e^ + e^ - \to e^ \pm W^ \mp \mathop {\nu _e }\limits^{( - )} \) are sensitive to the magnetic moment of theW. So, with this reaction, not onlyW bosons can be produced but also the gauge nature of the interaction can be tested. The decay \(Z^0 \to l^ \pm W^ \mp \mathop {\nu _l }\limits^{( - )} \) is discussed in view of its observation ine ⁺ e ^? experiments. Finally the crosssections ofe ^- p→ν _e W ^- X ⁺ are computed. They are of the order of 10^?38 cm² for \(\sqrt s \simeq 200\) GeV.     

On the helicity of charm jets

We discuss the determination of initial quark polarization from the characteristics of the jet it gives rise to, since theory indicates that quark-antiquark pairs produced ine ^? e⁺ annihilation have a large polarization correlation and that individual quarks have longitudinal polarization due to γ-Z ⁰ interference. On the basis of a model calculation, we deduce that the mean value of \(S_c \cdot \hat P_D \times \hat P_\pi \) for charm quark jets, averaged over theD ^*(2010), can be non zero and is then a measure of the initial quark helicity. Expectation values are, however, very small, for reasons which are discussed. The extension tob andt quarks is briefly considered.     

Gaussian limit for critical oriented percolation in high dimensions

In this paper, we consider the spread-out oriented bond percolation models inZ ^d ×Z withd>4 and the nearest-neighbor oriented bond percolation model in sufficiently high dimensions. Let η _n ,n=1, 2, ..., be the random measures defined onR ^d by $$\eta _n (A) = \sum\limits_{x \in Z^d } {1_A (x/\sqrt n )1_{\{ (0,0) \to (x,n)\} } } $$ The mean of η _n , denoted by $\bar \eta _n $ , is the measure defined by $$\bar \eta _n (A) = E_p [\eta _n (A)]$$ We use the lace expansion method to show that the sequence of probability measures $[\bar \eta _n (R^d )]^{ - 1} \bar \eta _n $ converges weakly to a Gaussian limit asn→∞ for everyp in the subcritical regime as well as the critical regime of these percolation models. Also we show that for these models the parallel correlation length $\xi (p)~|p_c - p|^{ - 1} $ asp?p_c