Search for Higgs bosons decaying into bb and produced in association with a vector boson in pp collisions at square root of s = 1.8 TeV

We present a new search for H0V production, where H0 is a scalar Higgs boson decaying into bb with branching ratio beta, and V is a Z0 boson decaying into e+e-, mu+mu-, or nunu. This search is then combined with previous searches for H0V where V is a W+/- boson or a hadronically decaying Z0. The data sample consists of 106 +/- 4 pb(-1) of pp collisions at square root of s = 1.8 TeV accumulated by the Collider Detector at Fermilab. Observing no evidence of a signal, we set 95% Bayesian credibility level upper limits on sigma(pp --> H0V) x beta. For H0 masses of 90, 110, and 130 GeV/c2, the limits are 7.8, 7.2, and 6.6 pb, respectively.     

Quantum orders in an exact soluble model

We find all the exact eigenstates and eigenvalues of a spin-1/2 model on square lattice: H=16g Sum S(y)(i)S(x)(i + empty set x)S(y)(i + empty set x + empty set y)S(x)(i + empty set y). We show that the ground states for g < 0 and g > 0 have different quantum orders described by Z2A and Z2B projective symmetry groups. The phase transition at g = 0 represents a new kind of phase transition that changes quantum orders but not symmetry. Both the Z2A and Z2B states contain Z2 lattice gauge theories at low energies. They have robust topologically degenerate ground states and gapless edge excitations.     

Study of D~0-D~0 mixing at a giga-Z linear collider

The possibility of studying D 0-D 0 mixing at a giga-Z linear collider "Z factory" where 10 9 hadronic Z 0 decays can be accumulated is examined.We discuss the sensitivity for the measurements of neutral D mixing parameters.These results are compared to those attainable at B factories.We find that the typical decay length of the neutral D mesons at Z factory is about 10 times larger than that at B factory.In addition,the resolution of the vertex detector of a giga-Z factory is 2-3 times better than that of B factory.The proper time resolution at Z factory is about 20-30 times better than that at B factory.Therefore the determination of the mixing parameters at a giga-Z factory is more precise.     

Search for single vectorlike quarks in pp ̄ collisions at √s=1.96 TeV

We present a search for hypothetical vectorlike quarks in pp ? collisions at √s=1.96 TeV. The data were collected by the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4 fb(-1). We select events with a final state composed of a W or Z boson and a jet consistent with a heavy object decay. We observe no significant excess in comparison to the background prediction and set limits on production cross sections for vectorlike quarks decaying to W+jet and Z+jet. These are the most stringent limits to date for electroweak single vectorlike quark production at hadron colliders.     

Charge localization in DNA fibers

We study by first-principles molecular dynamics the mechanism of electron hole (positive charge) localization in a laboratory realizable radical cation Z DNA crystal. We find that at room temperature structural deformation does not provide an efficient localization mechanism. Instead, we find evidence for the importance of changes in the protonation state for stabilizing the radical defect.     

Ising transition driven by frustration in a 2D classical model with continuous symmetry

We study the thermal properties of the classical antiferromagnetic Heisenberg model with both nearest (J1) and next-nearest (J2) exchange couplings on the square lattice by extensive Monte Carlo simulations. We show that, for J2/J1>1/2, thermal fluctuations give rise to an effective Z2 symmetry leading to a finite-temperature phase transition. We provide strong numerical evidence that this transition is in the 2D Ising universality class, and that T(c)-->0 with an infinite slope when J2/J1-->1/2.     

Search for a fourth-generation quark more massive than the Z0 boson in p&pmacr; collisions at radicals = 1.8 TeV

We present the results of a search for pair production of a fourth-generation charge -1 / 3 quark (b(')) in sqrt[s] = 1.8 TeV p&pmacr; collisions using 88 pb(-1) of data obtained with the Collider Detector at Fermilab. We assume that both quarks decay via the flavor-changing neutral current process b(')-->bZ(0) and that the b(') mass is greater than m(Z)+m(b). We studied the decay mode b(')b(');-->Z(0)Z(0)b&bmacr; where one Z0 decays into e(+)e(-) or &mgr;(+)&mgr;(-) and the other decays hadronically, giving a signature of two leptons plus jets. An upper limit on the sigma(p&pmacr;-->b(')b(');)x[B(b(')-->bZ(0))](2) is established as a function of the b(') mass. We exclude at 95% confidence level a b(') quark with mass between 100 and 199 GeV/c(2) for B(b(')-->bZ(0)) = 100%.     

Search for ZH → l+ l- bb production in 4.2 fb(-1) of pp collisions at sqrt[s] =1 .96 TeV

We present a search for the standard model Higgs boson produced in association with a Z boson in 4.2 fb(-1) of pp collisions, collected with the D0 detector at the Fermilab Tevatron at sqrt[s] =1 .96 TeV. Selected events contain one reconstructed Z → e+ e- or Z → μ+ μ- candidate and at least two jets, including at least one b-tagged jet. In the absence of an excess over the background expected from other standard model processes, limits on the ZH cross section multiplied by the branching ratios are set. The limit at M(H) = 115 GeV is a factor of 5.9 larger than the standard model prediction.     

Isospin dependence of nuclear multifragmentation in statistical model

The evolution of nuclear disintegration mechanisms with increasing excitation energy, from compound nucleus to multifragmentation, has been studied by using the Statistical Multifragmentation Model (SMM) within a micro-canonical ensemble. We discuss the observable characteristics as functions of excitation energy in multifragmentation, concentrating on the isospin dependence of the model in its decaying mechanism and break-up fragment configuration by comparing the A₀=200, Z₀=78 and A₀=200, Z₀=100 systems. The calculations indicate that the neutron-rich system (Z₀=78) translates to a fission-like process from evaporation later than the symmetric nucleus at a lower excitation energy, but gets a larger average multiplicity as the excitation energy increases above 1.0 MeV/u.     

First direct measurement of the parity-violating coupling of the Z0 to the s quark

We present the first direct measurement of A(s), the parity-violating coupling of the Z0 boson to the strange quark, using approximately 550 000 e(+)e(-)-->Z0-->hadrons events recorded by the SLC Large Detector with a polarized e(-) beam. We tagged Z0-->s&smacr; events by the absence of B or D hadrons and the presence in each hemisphere of a high momentum K+/- or K(0)(s). Fitting the polar angle distributions of the strangeness-signed thrust axis gave A(s) = 0.895+/-0.066(stat)+/-0.062(syst). The analyzing power and uu+d&dmacr; background were constrained using the data, greatly reducing any model dependence.     

New shape isomer in the self-conjugate nucleus 72Kr

A new isomeric 0(+) state was identified as the first excited state in the self-conjugate (N=Z) nucleus 72Kr. By combining for the first time conversion-electron and gamma-ray spectroscopy with the production of metastable states in high-energy fragmentation, the electric-monopole decay of the new isomer to the ground state was established. The new 0(+) state is understood as the band head of the known prolate rotational structure, which strongly supports the interpretation that 72Kr is one of the rare nuclei having an oblate-deformed ground state. This observation gives in fact the first evidence for a shape isomer in a N=Z nucleus.     

Limits on anomalous trilinear gauge couplings in Zγ events from pp¯ collisions at √s=1.96 TeV

Using Zγ candidate events collected by the CDF detector at the Tevatron Collider, we search for potential anomalous (non-standard-model) couplings between the Z boson and the photon. Zγ couplings vanish at tree level and are heavily suppressed at higher orders; hence any evidence of couplings indicates new physics. Measurements are performed using data corresponding to an integrated luminosity of 4.9 fb(-1) in the Z→ννˉ decay channel and 5.1 fb(-1) in the Z→l(+)l(-) (l=μ, e) decay channels. The combination of these measurements provides the most stringent limits to date on Zγ trilinear gauge couplings. Using an energy scale of Λ=1.5 TeV to allow for a direct comparison with previous measurements, we find limits on the CP-conserving parameters that describe Zγ couplings to be |h(3)(γ,Z)|<0.022 and |h(4)(γ,Z)|<0.0009. These results are consistent with standard model predictions.     

B physics at LEP

The Z factory at LEP is like a mini B factory. About 20% of the time a Z decays to a pair of b flavoured hadrons. As a result, this has provided a major boost to B physics studies. The four sophisticated LEP detectors, with millions of Z events, have provided a variety of interesting results. Only a snapshot of the major developments can be covered in one review. We have considered the results related to coupling, in particular, the measurements of R_b=Γ_b/Γ_had the forward backward charge asymmetry. The b hadron properties, like inclusive and exclusive lifetime measurements are summarised briefly. Measurements of oscillation parameter as well as the evidence for time dependent evolution have been discussed. Studies of interesting decay modes have been mentioned.     

The origin of reflection loss peaks in the double-layer electromagnetic wave absorber

We investigated the origin of reflection loss (RL) peaks of Co₂Z particle composite (t mm)/fake-shaped carbonyl iron (CI) particle composite (1.5 mm) double-layer absorbers backed by a perfect conductor in 0.1–18 GHz. The RL peak frequency in the low frequency region remains unvariable and the RL peak in the high frequency region moves to lower frequency with the increase of Co₂Z particle composite thickness. The investigation results indicated that the two RL peaks come from the quarter-wavelength cancellation at the interface from Co₂Z particle composite to CI particle composite and the interface from air to Co₂Z particle composite, respectively.     

The Exoticness and Realisability of Twisted Haagerup–Izumi Modular Data

The quantum double of the Haagerup subfactor, the first irreducible finite depth subfactor with index above 4, is the most obvious candidate for exotic modular data. We show that its modular data \({\mathcal{D}{\rm Hg}}\) fits into a family \({\mathcal{D}^\omega {\rm Hg}_{2n+1}}\) , where n ≥  0 and \({\omega\in \mathbb{Z}_{2n+1}}\) . We show \({\mathcal{D}^0 {\rm Hg}_{2n+1}}\) is related to the subfactors Izumi hypothetically associates to the cyclic groups \({\mathbb{Z}_{2n+1}}\) . Their modular data comes equipped with canonical and dual canonical modular invariants; we compute the corresponding alpha-inductions, etc. In addition, we show there are (respectively) 1, 2, 0 subfactors of Izumi type \({\mathbb{Z}_7, \mathbb{Z}_9}\) and \({\mathbb{Z}_3^2}\) , and find numerical evidence for 2, 1, 1, 1, 2 subfactors of Izumi type \({\mathbb{Z}_{11},\mathbb{Z}_{13},\mathbb{Z}_{15},\mathbb{Z}_{17},\mathbb{Z}_{19}}\) (previously, Izumi had shown uniqueness for \({\mathbb{Z}_3}\) and \({\mathbb{Z}_5}\)), and we identify their modular data. We explain how \({\mathcal{D}{\rm Hg}}\) (more generally \({\mathcal{D}^\omega {\rm Hg}_{2n+1}}\)) is a graft of the quantum double \({\mathcal{D} Sym(3)}\) (resp. the twisted double \({\mathcal{D}^\omega D_{2n+1}}\)) by affine so(13) (resp. so\({(4n^2+4n+5)}\)) at level 2. We discuss the vertex operator algebra (or conformal field theory) realisation of the modular data \({\mathcal{D}^\omega {\rm Hg}_{2n+1}}\) . For example we show there are exactly 2 possible character vectors (giving graded dimensions of all modules) for the Haagerup VOA at central charge c = 8. It seems unlikely that any of this twisted Haagerup-Izumi modular data can be regarded as exotic, in any reasonable sense.     

定容高压气体的压缩因子

１前言压缩因子是比较实际气体与理想气体之差异的重要物理量，从某状态的压缩因子Ｚ可求出该状态下实际气体的Ｐ或Ｖ来。现在高压气体的Ｚ大多是在高压ＰＶＴ实验台上用定容测试方法（绝对法）测试出来。但测试过程耗时费资，在新型气态工质不断涌现的今天，一些特殊高压高温条件很难在实验中满足；而工程上则多从对比态原理出发，从两参量或三参量的普遍化压缩因子图中近似求出，显然，其系统误差一般较大，一般说来，高压气体的Ｚ是系统温度Ｔ，压力Ｐ和偏心因子。的函数Ｚ＝Ｚ（Ｔ，Ｐ），其解析形式一直是热物性工作者努力探求的目标，…     

Search for high mass resonances decaying to muon pairs in √s=1.96 TeV pp collisions

We present a search for a new narrow, spin-1, high mass resonance decaying to μ(+)μ?+X, using a matrix-element-based likelihood and a simultaneous measurement of the resonance mass and production rate. In data with 4.6 fb?1 of integrated luminosity collected by the CDF detector in pp collisions at √s=1960 GeV, the most likely signal cross section is consistent with zero at 16% confidence level. We therefore do not observe evidence for a high mass resonance and place limits on models predicting spin-1 resonances, including M>1071 GeV/c2 at 95% confidence level for a Z' boson with the same couplings to fermions as the Z boson.     

An investigation of hadronization mechanism at a Z~0 factory

We briefly review the hadronization pictures adopted in the LUND String Fragmentation Model (LSFM),Webber Cluster Fragmentation Model (WCFM) and Quark Combination Model (QCM),respectively.Predictions of hadron multiplicity,baryon to meson ratios and baryon-antibaryon flavor correlations,especially those related to heavy hadrons at a Z 0 factory obtained by LSFM and QCM,are reported.     

A Graphical and Analytical Method to Determine the Transient Response for an Ideal Transmission Line, Loaded by a Time-Varying Impedance

Based on Bergeron's theory, a graphical and analytical method has been worked out to determine the dynamic load characteristic and load transients for a time-varying load impedance, pulsed by a lossless transmission line. The analytical solution has been compared with the numerical solution of the network analysis code SCEPTRE. A parametric study for a time-decreasing load function, demonstrated by the example of a vacuum-discharge flash X-ray tube, reveals that the dynamic load characteristic IL[UL(t), U0, Z0, T] and the transients UL(t, U0, Z0, T) and IL(t, U0, Z0, T) are dependent on the diode function ZL(t) as well as on the charging voltage U0 and the characteristics T and Z0 of the line.     

Ionization of xenon Rydberg atoms at a metal surface

Experiments in which a thermal-energy beam of xenon Rydberg atoms is directed at near grazing incidence onto a flat Au(111) surface are described that provide new insight into charge transfer and electron tunneling during atom/surface interactions. Analysis of the data shows that for the present range of principal quantum number n, 13 < or = n < or = 20, ionization occurs at an atom/surface separation Z(i) = (4.5+/-0.9)n2a0, where n2a0 is the Bohr radius of the atom. This result is in good agreement with the value Z(i) approximately 3.8n2a0 predicted by ab initio hydrogenic theory.