Semi-leptonic decays of charmed mesons produced in γN collisions

We report here on a study of the characteristics of the semileptonic decay spectra from a pair of charmed hadrons produced via photoproduction. The inclusive production of charmed hadrons is phenomenologically parametrized as e^?aze^?bp_t2. Their decays are described by (i) decay of free charm quark in GIM, (ii) K¹ dominant mode, $\text{D}\text{→}\text{K}{}^1\text{l}\text{ν}$, and (iii) pure leptonic decays. We deduce that 〈M_eμ²〉 = 0.18 M_D² for free quark decay and 〈M_eμ²〉 = ?0.35 +-0.24 M_D² for K¹ dominant decay. For the specific purpose of the photoproduction experiment at FNAL whicc is currently searching for μe events, we incorporate the incident photon spectrum, and the decay distributions with and without the experimental acceptance criteria are presented.     

Compilation of coupling constants and low-energy parameters

The electron capture decay ${}^{163}\text{Ho}\text{→}{}^{163}\text{Dy}{}^{\mathrm{<mtext>H</mtext>}}\text{+ν}{}_{\mathrm{<mtext>e</mtext>}}$ occurs with a record low energy release, Q ～ 2.6 keV. The daughter Dy^H atom has an electron hole, H, and predominantly decays by electron ejection Dy^H→Dy^H₁H₂+e^?. We investigate the neutrino mass sensitivity of the electron spectrum in the overall process Ho→Dy^H₁H₂+e^?+ν_e. In this spectrum, the fraction of events sensitive to a fixed non-zero neutrino mass in one to two orders of magnitude smaller than in the standard case of tritium β decay. But the electron energies in ¹⁶³Ho decay are considerably smaller than in ³H decay (Q ～ 18 keV). This suggests experiments whose energy resolution could be much better than that of the magnetic spectrometers conventionally used in the tritium case.     

Effects of multiplicity on charm semileptonic decay distributions

We consider the effects of multiplicity in semileptonic decays of charmed D(1.87) mesons, produced near threshold in e⁺e^? collisions. We calculate the decay distributions from uncorrelated D → (nπ)Kev and resonance dominated $\text{D}\text{→}\text{K}{}^1\text{e}\text{v}$ modes. Recent data from DORIS suggest that modes with two or more final hadrons dominate strongly.     

Crossing relations for deep-inelastic and annihilation processes

We calculate in a model field theory [φ³]_σ the structure functions $\text{F}\text{?}\text{(ω), F(ω)}$ for the processes e⁺+e^?→h+X and e^?+h→e^?+X in the next to leading logarithm approximation. We find that $\text{F}\text{(ω) and F(ω)}$ satisfy the analytic continuation relation but not the Gribov-Lipatov reciprocity relation.     

Second order QCD contributions to thrust and spherocity

In e⁺e^? annihilation there are regions of high spherocity S and low thrust $\text{T(S >}\text{16}\text{3π}{}^2\text{and}\text{T <}\text{2}\text{3}$ in which these distributions are given in QCD perturbation theory by the subprocesses e⁺e^? → qq?GG and e⁺e^? → qq?qq? neglecting only cubic and higher order terms in α_S. We give the corresponding QCD predictions which suggest that the calculable corrections to these variables may be slowly convergent.     

Exotic decays of the muon and heavy leptons in gauge theories

We have studied the decay ?₁ → ?₂ + γ for arbitrary like charged spin $\text{1}\text{2}$ leptons in a manner which is applicable to a large class of models. Our computations assume that this process is induced by one loop diagrams. When the leading effect is cancelled by a leptonic G.I.M. mechanism, we find an extremely large enhancement of O(M_W⁴/M_L⁴) in Λ(μ^?→e^?+e⁺e^?)/Λ(μ^?→e^?+γ) if the intermediate lepton is charged.     

Radiative decays of the Jψ and evidence for a new heavy resonance

The three photon final state produced in e⁺e^? collisions has been measured at the mass of the $\text{J}\text{ψ}$ resonance using the nonmagnetic part of the double arm spectrometer DASP. The decays $\text{J}\text{ψ}\text{→ ηγ, η'γ}$ and π^oγ were observed and their branching ratios are given. A four standard deviation signal was observed in the γγ mass spectrum at a mass of (2.83 ± 0.03) GeV. An upper limit is given for the direct decay $\text{J}\text{ψ}\text{→ 3γ}$.     

Baryon wave functions and nucleon decay

We apply to nucleon decay the knowledge about the short-distance structure of baryon wave functions gleaned from QCD form factor calculations nd the $\text{J}\text{gY →}\text{p}\text{?}\text{p}$ decay rate. We review the uncertainties arising when current algebra and PCAC are used to relate $\text{N}\text{→}\text{?}\text{+}$ meson decay rates to 〈0|qqq|N〉 matrix elements. We show that the relevant matrix elements are not directly related to those of the leading twist operators “measured” in conventional high momentum transfer physics, but argue for an indirect based on models that fit both form factor and $\text{J}\text{Ψ}$ decay data. We use these inputs to calculate the p → e⁺π⁰ decay rate in minimal SU(5) and other grand unified theories (GUTs) for a specified value of the heavy vector boson mass m_X. Our results combined with the recent experimental lower limit on this mode indicate that m_X > 2 × 10¹⁵ GeV in the minimal SU(5) GUT, and we derive analogous bounds for supersymmetric GUTs. Our calculated lifetime for a given value of m_X is considerably shorter than previous estimates made using non-relativistic SU(6) or the bag model, a difference traceable to the different normalizations of 2 and 3 quark wave functions at short distances.     

Event shapes in e+e− annihilation

We present a complete set of rotationally invariant observables (H_l) which characterizes the ‘shapes’ of final states in e⁺e^? annihilation. They are infrared stable when calculated in QCD perturbation theory. We compare the ‘shapes’ of final states from the processes $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→}\text{q}\text{q}\text{,}\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→}\text{q}\text{q}\text{(}\text{G}\text{)}$ and from the three-gluon decays of heavy vector mesons. We also consider the production and decay of heavy quarks and leptons. Using a realistic model for the development of hadron jets, we find that for c.m. energies above about 10 GeV, these processes may be clearly distinguished by their distributions in the H_l. We indicate how our analysis may be extended to deep inelastic lepton-hadron interactions and hadron-hadron collisions involving large transverse momenta.     

The QCD effective coupling constant in e+e− annihilation

The QCD effective coupling constant α_s(Q²) is determined by comparing the O(α_s)² jet-distributions with the high-energy e⁺e^? data from PETRA. We get α_s(Q² = 1225 GeV²) = 0.125 ± 0.01, which corresponds to $\text{Λ}{}_{\mathrm{<mtext>MS</mtext>}}\text{= 110}{}^{\mathrm{+70}}{}_{\mathrm{?50}}\text{MeV}$ with five flavours.     

On duality in e+e- annihilation

With the help of a relativistic generalization of a formula for the leptonic width of quarkonium in the quasiclassical approximation it is shown that the sum of a sufficiently large number of total cross sections for the production of the quarkonium state (Q$\text{Q}$)_n in e⁺e^- annihilation is equal to the total cross section for production of a quasi-free quark- antiquark pair Q$\text{Q}$.     

A search for massive photinos at petra

We have searched for the supersymmetric partner of the photon, the photino, by investigating two-photon and single photon final states in e⁺e^? collisions. No significant signals were observed, which excludes the existence of the photino in the mass range 0.08–18 GeV/c² at the 95% confidence level, subject to the assumptions d=(100 GeV)² and $\text{m}{}_{\mathrm{<mtext>e</mtext><mtext>?</mtext>}}\text{=40}\text{GeV}\text{/c}{}^2$, where d is the supersymmetry breaking scale parameter and $\text{m}{}_{\mathrm{<mtext>e</mtext><mtext>?</mtext>}}$ is the scalar electron mass.     

Limits on the couplings of ϱ′ (1300 Me) and rhov;″ (1700 MeV) to the photon and to the (ππ) system

The analysis of the reaction e⁺e^?→π⁺π^? measured at the e⁺e^? colliding beam machine ADONE shows that, if ?′ and ?″ exist, the cross sections compare as follows (taking the ? as the reference point): $\text{σ(}\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→ ? → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$: σ(e⁺e^? → ?′ → π⁺π^?): σ(e⁺e^? → ?″ → π⁺π^?) = 1: (7 ± 4) × 10^?3: (1 ± 5) × 10^?4. The square of the product of their couplings to the photon (γ_?) and the γγ system (g_?ππ) are derived.     

A comparison of πππ, Kππ, πKKKK system produced in the reactions meson +p→3 mesons + p

A comparison is made of the low-mass three-meson systems (πππ), (Kππ), $\text{(π}\text{K}\text{K}\text{)}$ and $\text{(}\text{K}\text{K}\text{K}\text{)}$ diffractively produced in the reaction meson + proton → three mesons + proton. Several striking similarities and a few important differences are observed: (i) the reactions are consistent with the assumption that the three mesons decay entirely into a 0^? meson and a 0⁺, 1^? or 2⁺ resonance; (ii) the three-meson mass spectra have a peak ≈ 250 MeV above the effective threshold M_eff of the dominant decay mode and then fall off approximately as (mass)^?3;(iii) the average spin 〈J〉 = 0.55 + 1.1 Q_eff, where Q_eff = M - M_eff; (iv) the average orbital angular momentum 〈l〉 increases according to 〈l〉 = 0.75 Q_eff; (v) the three-meson states are produced dominantly in unnatural spin-parity states and no evidence for their being resonant is found; (vi) the only natural spin-parity states found are the well-established 2⁺ resonances A₂ and K¹ (1420); they have similar properties to the non-resonant unnatural parity states except for a dip at t = 0 in the dσ/dt distributions; (vii) both the unnatural and natural spin-parity states are produced mostly by an exchange of natural parity; (viii) there is evidence for two types of production mechanism with different polarization properties, one approximately conserving helicity in the t-channel and the other in the s-channel.     

Radiative Z0 production: A method for neutrino counting in e+e− collisions

Radiative Z⁰ production in e⁺e^? collisions is analyzed as a method of measuring the partial width of the Z⁰ for decay into neutrinos and thus determining if there exist low mass neutral leptons beyond the three now known (ν_e,ν_μ,ν_τ). The conditions for observing the $\text{γν}\text{ν}$ final state are analyzed and background cross sections are determined. We conclude that the experiment is feasible and requires relatively modest apparatus.     

Neutral currents and stellar cooling

If weak neutral currents couple with the strengths suggested by recent experiments, then stellar cooling via neutrino pair emission from thermally excited nuclear states may be significant in white dwarfs with central temperature ?10^8° K. At higher temperatures, other neutrino cooling processes are more important. In the sun, the decay of thermally excited ⁵⁷Fe nuclei may produce a moderately large, but probably unobservable, low-energy flux of ν_μ, $\text{g}\text{?}\text{n}{}_{\mathrm{\mu }}$, ν_e, and $\text{g}\text{?}\text{n}{}_{\mathrm{e}}$ neutrinos.     

Neutral heavy lepton candidate in e+e− interactions

An event of the form e⁺e^? → μ⁺μ^? + (2 jets) recently observed at √s = 43.45 GeV is interpreted as production of a pair of neutral heavy leptons N, each with mass 20.5 ± 1.0 Gev/c². Two possibilities are explored: (i) the lepton is a wak isodoublet neutrino, produced in pairs by virtual Z⁰ decay. In this case, one expects $\text{B(}\text{Z}{}^0\text{→}\text{N}\text{N}\text{) ≈ 5\%}$; (ii) the lepton is a “right-handed neutrino”, produced in pairs via a new vector boson Z_χ. In this case, in one model, the Z_χ must lie between about 50 and 67 GeV/c². More generally, it must be very weakly coupled to ordinary quarks and leptons in order not to conflict with low-q² neutral-current data. Suggestions are made for further observation of N$\text{N}$ pairs and other effects of Z_χ in forthcoming e⁺e^? and p$\text{p}$ collisions.     

Observation of QCD effects in transverse momenta of e+e− jets

Probability distributions of the total transverse momenta (K⊥) of charged particles produced in hadronic jets in e⁺e^? annihilations have been measured for center of mass energies in the range from 9.2 to 31.6 GeV. A linear increase of the average K_⊥² with Q² is observed. The data are successfully compared with high order QCD predictions (according to a simple q$\text{q}$ picture supplemented by multiple emission of soft gluons). Deviations from this picture at the highest energies and large K_⊥ are then analyzed in terms of hard gluon bremsstrahlung and qualitative agreement is found with first order QCD predictions. Scaling “in the mean” is found to be valid both for jet and single particle transverse momenta.     

Jets fromQ \bar Q P waves

We discuss angular distributions and some kinematic features for jets originating from the decay of orbitally excitedQ \(\bar Q\) states. These can be produced ine ⁺ e ^? storage rings via the radiative decay of the first radial excitedQ \(\bar Q\) vector meson. We further present the complete and explicit angular distribution for the cascade decaye ⁺ e ^? → 2³ S ₁ →γ ₁+³ P _j,³ P _j →γ ₂+1³ S ₁, 1³ S ₁ →μ ⁺ μ ^? in all casesj=0, 1, 2. These distributions serve as a test of the spinj of intermediate states inQ \(\bar Q\) systems. By the photon—gluon analogy they can successfully be applied to the jet process, too.