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.     

SU(5) andSU(2)×U(1) radiative breakings inN=1 supergravity unified models

Non-minimalSU(5) supergravity GUTs are analyzed in order to obtain theSU(5) andSU(2)×U(1) breakings à la Coleman-Weinberg as dynamical effects generated by the soft breaking terms, residues of supergravityN=1 (minimally coupled). Solutions are found that predict the existence ofSU(2)-triplets andSU(3)-octets as heavy asO(1 TeV). Supersymmetric Higgs masses, of the same order than the gravitino mass, must be introduced for the heavy, Σ(24), and lightH ₁ (2),H ₂ (2) sectors. Imposing the experimental bound \(m_{\tilde g} \gtrsim 60GeV\) , the lower boundsm _3/2?30 GeV, \(m_{\bar e} > 140GeV\) \(m_{\bar u} > 133GeV\) are obtained.     

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.     

QCD bound state calculation of Dalitz decay form factors

We present calculations of the cross-sections and the forward-backward asymmetry forp \(\bar p\) →?⁺ ?^? +X in the framework of anSU(2)×U(1)×G model with two neutral gauge bosons [G=U(1) orSU(2)]. It is shown that a peak in the cross-section associated with a large asymmetry will characterize a deviation from the standard model.     

The decay of theT=1 isospin triplet inA=12 systems: IV. The energy dependence of the asymmetry coefficients\alpha _{\beta ^ \mp } of the beta-ray angular distribution in aligned12B and12N and the induced pseudotensor interaction

The asymmetry parameters \(\alpha _{\beta ^ \mp } \) of the beta-ray emitted from aligned¹²B and¹²N are evaluated as a function of the energy. The agreement with experimental differential data is excellent for both \(\alpha _{\beta ^ - } \) (W) and \(\alpha _{\beta ^ + } \) (W). This work confirms, using available nuclear model information, that no induced pseudotensor (IPT) interaction is required for a correct theoretical interpretation of the data. An upper limit for the IPT coupling constantf _T is determined from a simultaneous fit of \(\alpha _{\beta ^ - } \) (W) and \(\alpha _{\beta ^ + } \) (W).     

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.     

Measurements of hyperon semileptonic decays at the CERN Super Proton Synchrotron

The charged hyperon beam at the CERN Super Proton Synchrotron (SPS) has been used to collect data on semileptonic decays of Σ^?, Ξ^?, andΛ. A magnetic channel selected 100 GeV/c negatively charged particles produced in the forward direction by interaction of a 210 GeV/c proton beam on a BeO target. The Σ^? and Ξ^? hyperons were concurrently identified in a DISC ?erenkov counter, and their decay products were analysed by a magnetic spectrometer. Electron-hadron discrimination was achieved by the combined use of lead glass and lead/scintillator counters, transition radiation detectors, and a ?erenkov counter. In this article we report results on the \(\Xi \to \Lambda \pi (\Lambda \to pe\bar v), \Xi \to \Lambda e\bar v(\Lambda \to p\pi ),\) and \(\Xi \to \sum ^0 e\bar v(\sum ^0 \to \Lambda \gamma ) (\Lambda \to p\pi )\) decay modes. Samples of 7,111 \(\Lambda \to pe\bar v, 2,608 \Xi \to \Lambda e\bar v\) , and \(154 \Xi \to \Sigma ^0 e\bar v\) were used in our analysis. The branching ratio measurements gave values of (8.57±0.36)×10^?4, (5.64±0.31)×10^?4, and (0.87±0.17)×10^?4 for \(\Lambda \to pe\bar v, \Xi \to \Lambda e\bar v\) , and \( \Xi \to \sum ^0 e\bar v\) , respectively. Measurements of the Λ polarization and of the centre-of-mass distributions yield the axial vector to vector form factor ratio,g ₁/f ₁=+0.70±0.03 for \(\Lambda \to pe\bar v\) , andg ₁/f ₁=+0.25±0.05 for \(\Xi \to \Lambda e\bar v\) . The effects ofq ²-dependence off ₁ andg ₁ and of radiative corrections, the measurement of the weak magnetism termf ₂, and the effect of possible second-class current terms are discussed. Results on the \(\sum \to \Lambda e\bar v\) and \(\sum \to ne\bar v\) decay modes are reported in separate articles.     

Comparison of strange antibaryon and strange meson production inK + p interactions at 32 GeV/c

New experimental results are presented on inclusive production properties of \(\bar \Sigma ^{ * + } \) (1385) and \(\bar \Sigma ^{ * + } \) (1385) inK ⁺ p interactions at 32 GeV/c. The analysis is based on significantly larger statistics than previously available. A comparison is also made of invariantx-distributions ofK ⁰/ \(\bar K^0 \) , \(\bar \Lambda \) and \(\bar \Xi ^ + \) and of \(\bar \Sigma ^{ * \pm } \) (1385) andK ^*+(892). These spectra exhibit regularities expected from the quark-recombination picture when it is assumed that the strange mesons and antibaryons are produced off the strange \(\bar s\) -valence-quark in the incidentK ⁺ meson. Transverse momentum distributions are also presented forK ^*+(892) and \(\bar \Sigma ^{ * \pm } \) (1385) and found to be very similar. The results on strange antibaryon average multiplicities disagree strongly with a recent version of the additive quark model.     

Multi-quark structure ofU(3.1)

We interpret the recently observedU(3.1) mesons with the \(\Lambda \bar p\) + pions decays as the bound state of \(\Lambda ,\bar p\) andX ₀(1480). TheX ₀(1480) is a mesonium with \(Q^2 \bar Q^2 \) structures observed in γγ reactions and \(\bar pn\) annihilations. With this interpretation, we can understand its decay modes. Furthermore, we predict the ratio of \(\sigma (\Lambda \bar p\pi ^ + \pi ^ - )/\sigma (\Lambda \bar p\pi ^ + \pi ^ + )\) to be ?3.1 for centrally produced events and that the width of \(U^ - (\Lambda \bar p\pi ^ + \pi ^ - )\) to be greater than that of \(U^ + (\Lambda \bar p\pi ^ + \pi ^ + )\) . Both predictions seem to be in reasonable accord with the available data. We call for the detection of the \(\Lambda \bar p\pi ^ - \pi ^ - \) mode to verify the present interpretation.     

The static multipole moments of Δ1236(3/2,3/2) from superconvergence inNγ → Δπ scattering

Saturating superconvergence sum rules inNγ→Δπ scattering byN andΔ, we are able to relate the (isoscalar) dipole magnetic moment \(\tilde \mu _\Delta\) and the quadrupole electric moment \(\tilde Q_\Delta\) of the isobarΔ to the electric charge \(\tilde Z_\Delta\) and the dipole magnetic momentμ _N of the nucleonN. The numerical results are: \(\tilde \mu _\Delta \equiv \mu _{\Delta ^ + } + \mu _{\Delta ^0 } = 3.26\) (in unitse/2M)=2.48 (in unitse/2m), and \(\tilde Q_\Delta \equiv Q_{\Delta ^ + } + Q_{\Delta ^0 } = 0.050\) (in unitse/M ²)=0.029 (in unitse/m ²), whereM(m) is the mass ofΔ(N). Neglecting the pion mass and takingM=m,μ _n /μ _p =?2/3, we get theSU ₆ result μ_Δ+=μ _p .     

\bar \Lambda Production inK − p interactions at 32 GeV/c

Antilambda production is studied inK ^? p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive \(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ( \(\bar \Lambda \) ) increasing by a factor of four between 14.3 and 32 GeV/c. Thep _⊥ ² distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)^?2. Most of the \(\bar \Lambda \) 's are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for \(\bar \Lambda \) production inK ^- p→Λ \(\bar \Lambda \) +X K ^- p→ \(\bar \Lambda \) K ⁿ +X, andK ^- p→ \(\bar \Lambda \) p+X.     

Indecomposable representations with invariant inner product

Consequences of the existence of an invariant (necessarily indefinite) non-degenerate inner product for an indecomposable representation π of a groupG on a space \(\mathfrak{H}\) are studied. If π has an irreducible subrepresentation π₁ on a subspace \(\mathfrak{H}_1 \) , it is shown that there exists an invariant subspace \(\mathfrak{H}_2 \) of \(\mathfrak{H}\) containing \(\mathfrak{H}_1 \) and satisfying the following conditions: (1) the representation π ₁ ^# =π mod \(\mathfrak{H}_2 \) on \(\mathfrak{H}\) mod \(\mathfrak{H}_2 \) is conjugate to the representation (π₁, \(\mathfrak{H}_1 \) ), (2) \(\mathfrak{H}_1 \) is a null space for the inner product, and (3) the induced inner product on \(\mathfrak{H}_2 \) mod \(\mathfrak{H}_1 \) is non-degenerate and invariant for the representation $$\pi _2 = (\pi _2 |_{\mathfrak{H}_2 } )\bmod \mathfrak{H}_1 ,$$ a special example being the Gupta-Bleuler triplet for the one-particle space of the free classical electromagnetic field with \(\mathfrak{H}_1 \) =space of longitudinal photons and \(\mathfrak{H}_2 \) =the space defined by the subsidiary condition.     

A study of multiparticle fragmentation inK + p interactions at 32 GeV/c

Results are presented on inclusive production of resonant and non-resonant particle systems produced inK ⁺ p interactions at 32 GeV/c. We compareK ^*+(892), \(\bar \Sigma ^{ * - } \) (1385), Σ^*±(1385), and ?⁰ inclusivex-spectra with the ones of non-resonantK _s ⁰ π^±, \(\bar \Lambda \pi ^ - \) , Λπ^± and π⁺π^? pairs at the same effective mass. Resonance-particle pairsK ^*+π^±, Σ^*+π^?, and \(\bar \Sigma ^{ * - } \pi ^ - \) are also studied together with non-resonant tripletsK _s ⁰ π^±, Λπ⁺π^?, \(\bar \Lambda \pi ^ - \pi ^ - \) . The invariantx-spectra of resonant particle pairs decrease less rapidly withx then the corresponding non-resonant pairs. Comparison with quark-recombination predictions indicates that the particles, resonances and multiparticle systems are probably created off a single valence quark or diquark instead of carrying all possible valence-quarks.     

Neutrino production of same-sign dimuons at the Fermilab Tevatron

The rate of neutrino- and antineutrino-induced prompt same-sign dimuon production in steel was measured using a sample of μ^?μ^? events and 25 μ⁺μ⁺ events withP _μ>9 GeV/c, produced in 1.5 millionv _μ and 0.3 million \(\overline {v_\mu }\) induced charged-current events with energies between 30 GeV and 600 GeV. The data were obtained with the Chicago-Columbia-Fermilab-Rochester (CCFR) neutrino detector in the Fermilab Tevatron Quadrupole Triplet Neutrino Beam during experiments E 744 and E 770. After background subtraction, the prompt rate of same-sign dimuon production is (0.53±0.24)×10^?4 perv _μ charged-current event and (0.52±0.33)×10^?4 per \(\overline {v_\mu }\) charged-current event. The kinematic distributions of the same-sign dimuon events after background subtraction are consistent with those of the non-prompt background due to meson decays in the hadron shower of a charged-current event. Calculations ofc \(\bar c\) gluon bremsstrahlung, based on improved measurements of the charm mass parameter and nucleon structure functions by the CCFR collaboration, yield a prompt rate of (0.09±0.39)×10^?4 perv _μ charged-current event. In this case,c \(\bar c\) gluon bremsstrahlung is probably not an observable source of prompt same-sign dimuons.     

Strong decays ofΨ(4.03) andΨ(4.16) as radial excitations of charmonium

Considering the signals detected at 4.03 and 4.16 GeV as radial excitations of charmonium, we study their relative decay rates intoD \(\bar D\) ,D \(\bar D^* \) ,D ^* \(\bar D\) ,D ^* \(\bar D^* \) . We point out that one can understand these two peaks as ac \(\bar c\) 3S?2D wave state system with a large mixing angle in a Coulomb+linear interquark potential. We also examine the possibility that these two signals are respectively 3S and 4S wave excitations by studying a logarithmic charmonium potential model. We show that both these interpretations lead to drastically different predictions for the Ψ (4.16) decay rates (eitherD \(\bar D^* \) +D ^* \(\bar D\) orD \(\bar D\) mode is strongly suppressed) which would be very instructive to test experimentally.     

Magnetic moment of ∑− from dispersion relations int

Magnetic moments of baryons are calculated from dispersion relations int, including the π \(\bar \pi \) -continuum. The largest deviation from the naiveSU(3)-expectation is found for∑ ^?, leading to μ₂₂₁₁=?1.80 nuclear magnetons instead of ?0.66.     

Ξ Resonances in Ξ− Be interactions II. Properties of Ξ(1820) and Ξ(1960) in the\Lambda \bar K^0 and\Sigma ^0 \bar K^0 channels

In an experiment at the CERN-SPS charged hyperon beam, we have investigated the inclusive \(\Lambda \bar K^0 \) and \(\Sigma ^0 \bar K^0 \) final states formed in Ξ^? Be interactions. In the \(\Lambda \bar K^0 \) channel, we observe a signal at 1826 MeV/c² which can be identified with the known Ξ(1820) resonance. We determine its mass and width to be:M=1826±4 MeV/c², Г=12±14 MeV/c². A moment analysis is consistent with a spin of 3/2 and indicates a negative parity for this spin assignment. Also in the \(\Lambda \bar K^0 \) channel, we observe a 3.6σ signal with the following parameters:M=1963±5 MeV/c², Г=25±15 MeV/c². This state, which we call Ξ(1960), is not observed in the \(\Sigma ^0 \bar K^0 \) channel, leading to an upper limit on the ratio of partial widths \(\Sigma \bar K/\Lambda \bar K\) of 2.3 (90% confidence level). A moment analysis of the \(\Lambda \bar K^0 \) final state indicates a spin of 5/2 or greater in the natural spin-parity series 5/2⁺, 7/2^?, etc.     

On neutrino-electron interactions with neutrinos from theK L 0 decay

AK _L ⁰ induced beam ofv _e , \(\bar v_e \) ,v _μ , \(\bar v_\mu \) may be used to study \(\mathop {v_e }\limits^{( - )} e\) scattering. We have analyzed some details of this process and present arguments in favour of this type of beam. The main interesting point of \(\mathop {v_e }\limits^{( - )} e\) scattering is the test of a neutral current contribution which should yield a relatively large negative interference with the charged current. The possible influence of neutrino oscillations is discussed.     

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.