共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Ali J. G. Körner G. Kramer J. Willrodt 《Zeitschrift fur Physik C Particles and Fields》1979,1(2):203-213
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. 相似文献
2.
We analyze the phenomenon of heavy quark condensation within the framework of the QCD sum rule approach. We discuss two alternative expansions for massive quark condensates. The first one (heavy to light quark expansion), introduced by Broadhurst and Generalis, establishes a connection between the heavy and light quark worlds. The other one (heavy quark expansion) is valid when only heavy quark systems are considered. As a byproduct we have obtained the coefficients of \(\left\langle {\bar qq} \right\rangle \) , \(\left\langle {\bar qGq} \right\rangle \) , 〈G 2〉 and 〈G 3〉 for all bilinear currents. 相似文献
3.
Using constraints from weak hadronic process we obtain bounds on the right handed gauge boson mass and the flavour changing neutral Higgs masses. The masses of these bosons are in the multi-TeV region. A fit to the quark mixing angle reveals no dramatic changes compared to the standard W-S model. We present some prediction for the \(B^0 \overline {B^0 }\) system. 相似文献
4.
We study the charge properties of quark jets within a chain decay model for quark jet fragmentation. Using the charge properties of quark jets, we define charge-charge two-jet cross sections and correlations. In \(\bar pp\) collisions these correlations show significant structure due to the weak vector bosonsW ± andZ 0. 相似文献
5.
TS ENKHBAT 《Pramana》2012,79(4):879-882
A study of bound states of the fourth-generation quarks in the range of 500?C700 GeV is presented, where the binding energies are expected to be mainly of Yukawa origin, with QCD subdominant. Near degeneracy of their masses exhibits a new ??isospin??. The production of a colour-octet, isosinglet vector meson via $q\bar q \to \omega_8$ is the most interesting. Its leading decay modes are $\pi_8^\pm W^\mp$ , $\pi_8^0Z^0$ , and constituent quark decay, with $q\bar q$ and $t\bar t'$ and $b\bar b'$ subdominant. The colour octet, isovector pseudoscalar ?? 8 meson decays via constituent quark decay, or to Wg. This work calls for more detailed study of fourth-generation phenomena at LHC. 相似文献
6.
We systematically exploit the reported data on \(F_2^{\gamma p} ,F_2^{\gamma n} ,\sigma ^{vN} ,\sigma ^{\bar vN} ,\left\langle {xy} \right\rangle _{vN} ,\left\langle {xy} \right\rangle _{\bar vN} ,\left\langle {1 - y} \right\rangle _{vN} \) and \(\left\langle {1 - y} \right\rangle _{\bar vN} \) in order to test various versions of the quark parton model and to obtain further predictions. 相似文献
7.
J. C. Kluyver 《Zeitschrift fur Physik C Particles and Fields》1979,2(4):351-354
If theS-meson is assumed to be a baryonium state composed of an isospin one diquark and antidiquark, it will be produced in \(\bar pp\) reactions as a mixture ofI=0 andI=1 baryonium states. The experimentally observed large ratio of the cross sections of the reactions \(\bar pp \to S \to \bar pp\) and \(\bar pp \to S^0 \to \bar nn\) is then explained on basis of quark additivity and conservation of isospin in thes-channel. The model predicts: \(\sigma (\bar pp \to S^0 \to \bar pp):\sigma (\bar pp \to S^0 \to \bar nn):\sigma (\bar pn \to S^ - \to \bar pn) = 25:1:16\) . 相似文献
8.
We show that three-quark axial currents as required by broken SU(6) spin-flavor symmetry reduce the quark spin contribution to proton spin from \({{\Sigma}_p = 1}\) (one-quark axial current value) to \({{\Sigma}_p = 0.41(12)}\) consistent with the empirical value \({{\Sigma}_{p, exp} = 0.33(08)}\) . In the case of the \({{\Delta}^+(1232)}\) baryon, we find that three-quark axial currents increase the one-quark axial current value \({{\Sigma}_{{\Delta}^+} = 3}\) to \({{\Sigma}_{{\Delta}^+} = 3.87(22)}\) . We also calculate the quark orbital angular momenta L u and L d in the proton and \({{\Delta}^+}\) and interpret our results in terms of the prolate and oblate geometric shapes of these baryons consistent with their intrinsic quadrupole moments. 相似文献
9.
V. F. Kurshetsov Yu. M. Antipov A. V. Artamonov V. A. Batarin O. V. Eroshin V. Z. Kolganov A. S. Konstantinov A. P. Kozhevnikov A. E. Kushnirenko L. G. Landsberg V. M. Leontiev G. S. Lomkatsi V. V. Molchanov V. A. Mukhin A. F. Nilov D. I. Patalakha S. V. Petrenko V. T. Smolyankin D. V. Vavilov V. A. Victorov 《Physics of Atomic Nuclei》2005,68(3):439-454
A search for narrow Θ+(1540), a candidate for a pentaquark baryon with positive strangeness, has been performed in an exclusive proton-induced reaction $p + C(N) \to \Theta ^ + \bar \kappa ^0 + C(N)$ on carbon nuclei or quasifree nucleons at $E_{beam} = 70GeV(\sqrt s = 11.5GeV)$ studying nK +, pK S 0 , and pK L 0 decay channels of Θ+(1540) in four different final states of the $\Theta ^ + \bar K^0 $ system. In order to assess the quality of the identification of the final states with neutron or K L 0 , we reconstructed Λ(1520) → nK S 0 and ? → K L 0 K S 0 decays in the calibration reactions p + C(N) → Λ (1520)K ++C(N) and p+C(N) → p?+C(N). We found no evidence for a narrow pentaquark peak in any of the studied final states and decay channels. Assuming that the production characteristics of the $\Theta ^ + \bar K^0 $ system are not drastically different from those of the Λ(1520)K + and p? systems, we established upper limits on the cross-section ratios $\sigma (\Theta ^ + \bar K^0 )/\sigma (\Lambda (1520)K^ + ) < 0.02$ and $\sigma (\Theta ^ + \bar K^0 )/\sigma (p\phi ) < 0.15$ at 90% C.L. and a preliminary upper limit for the forward-hemisphere cross section $\sigma (\Theta ^ + \bar K^0 )$ nb/nucleon. 相似文献
10.
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. 相似文献
11.
In composite models of quarks, leptons and weak bosons whereW-constituents are colored objects, color octet partners ofW ± andZ 0 are predicted. We study in detail the phenomenology of these particles. Independent of the specific model one expects a color octet isotriplet of vector bosons (W 8 ± ,Z 8 0 ) with mass in the range of 100–200 GeV, and a color octet isosinglet vector bosonV 8 0 with substantially larger mass, due to mixing with the gluon. Moreover, relatively light color octet excitations of the leptons appear, while the existence of “color exotic” partners of the quarks is model dependent. These particles decay mainly into a lepton (quark) and a gluon. We construct the couplings ofW 8 ± ,Z 8 0 andV 8 0 to ordinary and “color exotic” fermions. The signals of color octet weak bosons in low energy weak reactions are explored in detail. The production cross section ofW 8 ± (Z 8 0 ) in hadron-hadron collisions is calculated for \(0.54TeV \leqq \sqrt s \leqq 20TeV\) . Various decay modes of colored weak bosons are studied. The most prominent decay signatures ofW 8 ± andZ 8 0 are events of the type (l +-: charged lepton;j: hadronic jet; : missing transverse momentum). The present CERN \(p\bar p\) collider data on such events are discussed in the light ofW 8 ± andZ 8 0 decays. If colored weak bosons are not found with a mass less than ~250 GeV composite model building will be strongly restricted. 相似文献
12.
Saurabh D. Rindani 《Pramana》2003,61(1):33-50
In the presence of an electric dipole coupling of $\overline {tt} $ to a photon, and an analogous ‘weak’ dipole coupling to the Z, CP violation in the process e+e? → $\overline {tt} $ results in modified polarization of the top and the anti-top. This polarization can be analyzed by studying the angular distributions of decay charged leptons when the top or anti-top decays leptonically. Analytic expressions are presented for these distributions when eithert or $\overline t $ decays leptonically, including $\mathcal{O}$ (αs) QCD corrections in the soft-gluon approximation. The angular distributions are insensitive to anomalous interactions in top decay. Two types of simple CP-violating polar-angle asymmetries and two azimuthal asymmetries, which do not need the full reconstruction of thet or $\overline t $ , are studied. Independent 90% CL limits that may be obtained on the real and imaginary parts of the electric and weak dipole couplings at a linear collider operating at √ s = 500 GeV with integrated luminosity 500 fb? and also at √s = 1000 GeV with integrated luminosity 1000 fb? have been evaluated. The effect of longitudinal electron and/or positron beam polarizations has been included. 相似文献
13.
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. 相似文献
14.
The observability of a charged Higgs boson produced in association with a W boson at future muon colliders is studied. The analysis is performed within the MSSM framework. The charged Higgs is assumed to decay to $t\bar{b}We study $B_{s}^{0} \to J/\psi f_{0}(980)$ decays, the quark content of f 0(980) and the mixing angle of f 0(980) and ??(600). We calculate not only the factorizable contribution in the QCD factorization scheme but also the nonfactorizable hard spectator corrections in QCDF and pQCD approach. We get a result consistent with the experimental data of $B_{s}^{0} \to J/\psi f_{0}(980)$ and predict the branching ratio of $B_{s}^{0}$ ?CJ/???. We suggest two ways to determine f 0?C?? mixing angle ??. Using the experimental measured branching ratio of $B_{s}^{0} \to J/\psi f_{0}(980)$ , we can get the f 0?C?? mixing angle ?? with some theoretical uncertainties. We suggest another way to determine the f 0?C?? mixing angle ?? using both experimental measured decay branching ratios $B_{s}^{0} \to J/\psi f_{0}(980) (\sigma)$ to avoid theoretical uncertainties. 相似文献
15.
The implications of the model with a SU(2)-singlet up-type quark, heavy enough not to be produced at the LHC, namely, the contribution of the new quark to the branching ratios of the K → πν $ \bar \nu $ , B → πν $ \bar \nu $ , and B → Kν $ \bar \nu $ decays are investigated. It is shown that the deviation from the Standard Model can be up to 10% in the case of a 5-TeV quark. Precise measurements of these branching ratios in future experiments will allow for the observation of the contributions of the new quark or to impose stronger constraints on its mass. 相似文献
16.
A. Ali 《Zeitschrift fur Physik C Particles and Fields》1979,1(1):25-41
Motivated by the discovery of λ(9.4), we study the semileptonic decay correlations of the next heavy quark, and their consequences for thee + e ? colliding beam and neutrino experiments. A detailed comparison is made with the corresponding correlations from the production and decay of charm and heavy leptons, τ±. Some tests of the \({\rm B}^0 - \bar {\rm B}^0 \) mixing ( \(B = b\bar q\) withbaQ=?1/3 heavy quark) are suggested fore + e ? colliding beam experiments. 相似文献
17.
Massimo Campanino Abel Klein J. Fernando Perez 《Communications in Mathematical Physics》1991,135(3):499-515
We study the zero-temperature behavior of the Ising model in the presence of a random transverse field. The Hamiltonian is given by $$H = - J\sum\limits_{\left\langle {x,y} \right\rangle } {\sigma _3 (x)\sigma _3 (y) - \sum\limits_x {h(x)\sigma _1 (x)} } $$ whereJ>0,x,y∈Z d, σ1, σ3 are the usual Pauli spin 1/2 matrices, andh={h(x),x∈Z d} are independent identically distributed random variables. We consider the ground state correlation function 〈σ3(x)σ3(y)〉 and prove:
- Letd be arbitrary. For anym>0 andJ sufficiently small we have, for almost every choice of the random transverse fieldh and everyx∈Z d, that $$\left\langle {\sigma _3 (x)\sigma _3 (y)} \right\rangle \leqq C_{x,h} e^{ - m\left| {x - y} \right|} $$ for ally∈Z d withC x h <∞.
- Letd≧2. IfJ is sufficiently large, then, for almost every choice of the random transverse fieldh, the model exhibits long range order, i.e., $$\mathop {\overline {\lim } }\limits_{\left| y \right| \to \infty } \left\langle {\sigma _3 (x)\sigma _3 (y)} \right\rangle > 0$$ for anyx∈Z d.
18.
19.
An investigation of inclusivepp→π?+? in terms of the covariant Boltzmann factor (BF) including the chemical potential μ indicates a) that the temperatureT increases less rapidly than expected from Stefan's law, b) that a scaling property holds for the fibreball velocity of π? secondaries, leading to a multiplicity law like ~E cm 1/2 at high energy, and c) that μπ is related to the quark mass: μπ=2m q ?m π the quark massm q determined by \(T_{\pi ^ - } \) at \(\bar pp\) threshold beingm q =3Tπ?330 MeV. Because ofthreshold effects \(T_{\bar p}< T_{\pi ^ - } \) , whereas \({{\mu _p } \mathord{\left/ {\vphantom {{\mu _p } {\mu _{\pi ^ - } }}} \right. \kern-0em} {\mu _{\pi ^ - } }} \simeq {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-0em} 2}\) as expected from the quark contents of \(\bar p\) and π. The antinuclei \(\bar d\) and \({{\bar t} \mathord{\left/ {\vphantom {{\bar t} {\overline {He^3 } }}} \right. \kern-0em} {\overline {He^3 } }}\) observed inpp events are formed by coalescence of \(\bar p\) and \(\bar n\) produced in thepp collision. Semi-empirical formulae are proposed to estimate multiplicities of π?, \(\bar p\) and antinuclei. 相似文献
20.
M. Capdequi-Peyranere J. Layssac G. Moultaka 《Zeitschrift fur Physik C Particles and Fields》1988,39(4):525-533
We study the effects of composite quarks and leptons in toponium physics. Introducing two kinds of non-standard four fermion effective couplings involving top quarks, we compute their influence on \(\theta (t\bar t)\) widths, on cross-sections and asymmetries for \(e^ + e^ - \to \theta \to l\bar l\) , \(q\bar q\) and single quark decay modes. New bounds on four quark contact terms can be inferred at the energies of LEP I and SLC. 相似文献