W-Boson mass operator in an external magnetic field at high temperatures

By the Schwinger proper-time method, the one-loop contribution to the W-boson mass operator is calculated in a constant magnetic field at high temperatures. The static limit is investigated. By averaging the mass operator over the physical states of a vector particle, the temperature-dependent radiative corrections to the W-boson energy spectrum are obtained at high magnetic fields (eH/M ²?1) for various values of the spin projection onto the field direction. These corrections are found to be positive. In particular, the correction to the ground-state level stabilizes the W-boson vacuum state at high temperatures.     

Electroweak radiative corrections to the top quark decay

The top quark, once produced, should be an important window to the electroweak symmetry breaking sector. We compute electroweak radiative corrections to the decay processt→b+W ⁺ in order to extract information on the Higgs sector and to fix the background in searches for a possible new physics contribution. The large Yukawa coupling of the top quark induces a new form factor through vertex corrections and causes discrepancy from the tree-level longitudinalW-boson production fraction, but the effect is of order 1% or less form _H<1 TeV.     

Double Higgs production at the linear colliders and the probing of the Higgs self-coupling

We study double Higgs production in the e⁺e^? and γγ modes of the linear collider. It is also shown how one can probe the scalar potential in these reactions. We discuss the effective longitudinal W approximation in γγ processes and the W _LW_L luminosities in the two modes of a high-energy linear collider. A generalised non-linear gauge-fixing condition, which is particularly useful for tree-level calculations of electroweak processes for the laser induced collider, is presented. Its connection with the background-field approach to gauge fixing is given.     

Higgs boson bremsstrahlung in top quark decay

In top quark decay a neutral Higgs boson may be emitted in bremsstrahlung from the top quark or from the W-boson. We evaluate the branching fraction for this hitherto overlooked t→H⁰bW⁺ decay mode, where the W⁺ can be virtual or real. It has the standard model values of 0.02%, 0.2%, 0.8% for m_t=50, 100, 200 GeVand m_H=10 GeV.     

High-resolution Fourier spectrometry of 14N2 and 15N2 infrared emission spectrum: Extensive analysis of the W3Δu - B3Πg system

The infrared spectrum of the nitrogen molecule, excited in a microwave discharge, has been recorded in high resolution by Fourier spectrometry in the range 2500–15 000 cm^?1. The precision of the measurements is estimated to be about 0.003 cm^?1. We have analyzed 19 bands of the W³Δ_u-B³Π_g system of ¹⁴N₂, with 0 ≤ v′ ≤ 7, and three bands of ¹⁵N₂ lying between 2500 and 5900 cm^?1. The molecular constants of the ³Δ_u and B³Π_g states have been determined by direct approach using an iterative nonlinear least-squares procedure. It has proved convenient to describe the levels of W³Δ_u state in a case a basis although in fact they approximate those of Hund's case b. Derived values of equilibrium constants of W³Δ_u are, in cm^?1: T_e = 8875.3347 (with origin taken in A, ³Σ_u⁺v = 0 level); ω_e = 1506.4859; ω_eχ_e = 12.5469; B_e = 1.4702537; α_B = 0.0170389; D_e = 0.55958 × 10^?5. RKR potential energy curves for the two states are constructed, and the Franck-Condon factors calculated for the W-B system.     

Heavy fermion contributions to the anomalous magnetic dipole and quadrupole moments of theW-boson

The contribution of a massivet-quark to the anomalous magnetic moment (Δκ) and the quadrupole moment (ΔQ) of theW-boson is calculated. An upper bound of Δκ=1.5×10^?2 and ΔQ=2.5×10^?3 for the standard model is obtained. Additional contributions from extraE ₆ fermions is also discussed.     

Measurement of ${M_{W^{+}}-M_{W^{-}}}$ at LHC

This paper is the second of the series of papers proposing dedicated strategies for precision measurements of the Standard Model parameters at the LHC. The common feature of these strategies is their robustness with respect to the systematic measurement and modeling error sources. Their impact on the precision of the measured parameters is reduced using dedicated observables and dedicated measurement procedures which exploit flexibilities of the collider and detector running modes. In the present paper we focus our attention on the measurement of the charge asymmetry of the W-boson mass. This measurement is of primordial importance for the LHC experimental program, both as a direct test of the charge-sign-independent coupling of the W-bosons to the matter particles and as a necessary first step towards the precision measurement of the charge-averaged W-boson mass. We propose and evaluate the LHC-specific strategy to measure the mass difference between the positively and negatively charged W-bosons, M_W⁺-M_W^-M_{W^{+}}-M_{W^{-}} . We show that its present precision can be improved at the LHC by a factor of 20. We argue that such a precision is beyond the reach of the standard measurement and calibration methods imported to the LHC from the Tevatron program.     

Prediction for Z-mass is a crucial test of the standard model

In schemes with oneW boson and twoZ-bosons (mediating the charged and neutral current interactions involving ordinary fermions) based on the direct product and simple groups, SU(2) × U(1) ×u′(1) andG × U(1) (G is a simple group of rank two), the following two questions are discussed. (1) What are the necessary and sufficient conditions for minimal reducibility of the effective four-fermion neutral current interaction (involving ν_μ-hadron, electron-hadron and ν_μ-electron sectors) to the corresponding prediction of the standard model? (2) In what way are the masses of the twoZ-bosons constrained relative to the mass of the neutral boson of standard model? The answers to these questions are given first by keeping the underlying Higgs structure, responsible for gauge-boson (and fermion) mass generation, completely arbitrary (called Higgs-independent case) and then by making a specific choice for the Higgs structure resulting in a natural mass relation for theW andZ-bosons that is an exact counterpart toM _W ^(S)/2 =M _Z ^(S)/2 sec² ? _W for the standard model (called Higgs-dependent case). The distinction between these two cases is brought out clearly as also that between the direct product and simple groups. Whether or not any assumption is made about the Higgs structure, with either the direct product or the simple group, it is concluded that in general there is aZ-boson lighter than the neutral boson of the standard model.     

Monte Carlo calculation of SU(2) glueball states with Symanzik's tree-level improved action

With the tree-level improved 4d SU(2) lattice gauge theory we carry out a Monte Carlo calculation of the spectrum. We find a scaling window for the 0⁺ state, leading to m(0⁺) ≈ 53 Λ^TI_L. Results for the 2⁺ state are somewhat inconclusive but also consistent with scaling.     

The use of electron impact dissociation and the photon-photon cascade technique to measure the lifetime of the B2Σ+ state of CN

The lifetime of the (B³Σ⁺_{υ= 0, 1} state of the CN radical has been measured by the photon-photon delayed coincidence technique, the CN radical being produced by electron impact dissociation of acetonitrile. This is the first lifetime measurement in a free radical by this method. The optical cascade in the band spectrum of CN used for the present measurement is H²Π_r - B²Σ⁺ - X²Σ⁺. The lifetime of the (B²Σ⁺)_{υ=0, 1} state in CN has been found to be 61.1 ± 7.6 ns.     

How gluon bremsstrahlung inW-decays distorts the experimental signature ofe + e −→W + W −

The effect of gluon bremsstrahlung in the decays of theW-bosons on the measurement of the reactione ⁺ e ^?→W ⁺ W ^?→ hadrons is discussed. From simulation studies we find a substantial fraction of events with high jet multiplicities. At energies of \(\sqrt s = 200\) GeV this leads to probabilities of 25% or higher to misassign a jet to aW-boson when a realistic resolution of a detector is assumed. Some implications on the measurement of the decay and production properties of theW's are discussed.     

Magnetic and ESR studies of Er3+ in lanthanum dihydride LaH2

Er³⁺ electron spin resonance ESR and magnetic susceptibility have been studied in metallic lanthanum dihydride host. The ESR spectrum contains a single asymmetrical line with g-factor g = 6.68 ± 0.05 close to that expected for Γ₇ as ground state. The experimental magnetic susceptibility was interpreted on the base of LLW cubic crystal field Hamiltonian. The best fit of the experimental data has been obtained for the following B₄ and B₆ crystal field parameters: B₄ = ?5.2 × 10^?3 K; B₆ = 3.8 × 10^?5 K which support the anionic-like character hydridic model of hydrogen atoms in this hydride.     

Limits to possible scalar-boson mass and coupling from e+e− collisions

Measurements of e⁺e^? → e⁺e^? at 2.8 GeV are reported and interpreted in terms of limits for the mass and coupling of a possible scalar boson of the type introduced in recent renormalizable models of weak interactions. In particular, in the Georgi-Glashow scheme of leptons we find that the scalar boson mass must be larger than 10 GeV for an m_W = 10 GeV (m_W mass of the W-boson) and of 6.5 GeV for m_W = 15 GeV. Alternatively its coupling is extremely weak.     

Microwave spectrum of 2-chloropyridine

The microwave spectrum of 2-chloropyridine, C₅H₄NCl, has been studied in the frequency range from 26.5–40.0 GHz. The spectrum is characterized by strong parallel type transitions of a near-prolate asymmetric top. The assigned transitions have been used to evaluate the ground state rotational constants of the two chlorine isotopes. The rotational constants are (in MHz): A = 5872.52, B = 1637.83, C = 1280.48 for the ³⁵Cl isotopic species and A = 5872.16, B = 1591.76, C = 1252.17 for the ³⁷Cl isotopic species. The small inertial defect indicates the molecule is planar. In addition an excited vibrational state of C₅H₄N³⁵Cl has been observed and analyzed. The chlorine quadrupolar coupling constants were determined for the ground state and are: χ_aa = ?71.9 MHz for ³⁵Cl and χ_aa = ?54.9 MHz for ³⁷Cl. By assuming the pyridine ring structure the CCl bond length is found to be 1.72 Å.     

Infrared spectrum of boron chloride (BCl)

The spectrum of the Δv = 1 band of BCl was measured between 828 and 870 cm^?1 with a tunable diode laser. The absorptions of the v = 1-0, 2-1, 3-2, and 4-3 transitions of BCl were observed in both a microwave discharge and a dc discharge through BCl₃. Spectra of ¹¹B³⁵Cl, ¹¹B³⁷Cl, ¹⁰B³⁵Cl, and ¹⁰B³⁷Cl were observed in natural abundance. A set of eight Dunham coefficients was determined by fitting the data for all observed isotopic species with the appropriate reduced mass factors. A BCl bond distance, r_e = 0.1715283(31) nm, was determined which agrees with the value derived from the electronic spectrum of BCl. The band center for the v = 1-0 transition of ¹¹B³⁵Cl is ν₀ = 829.4087(8) cm^?1.     

New physics from custodial SU(2) symmetricW interactions at supercolliders

We discuss the observability at LHC or SSC of anomalous 3-boson and 4-boson couplings generated by the SU(2)c preserving operatorO _w . We compute the invariant mass distribution of vector boson pair production viaq \(\bar q\) annihilation and via boson-boson fusion, for all possible channels. both these mechanisms are found to give comparable contributions for SSC and LHC, irrespective of whetherO _w exists or not. We find that the channelsWZ andWγ are particularly suitable for studying whetherO _w really appears in nature, and conclude that an upper limit on the strength of such an interaction which is better than |λ _W |<0.01, should be achievable. This will make a considerable improvement as compared to the indirect limits presently available from LEP1 (|λ _W |<0(1)), and expected from LEP2 (|λ _W |<0(0.1)).     

ΔB = 2 transitions in supersymmetric theories

We carry out a systematic analysis of ΔB = 2 interactions in supersymmetric theories. The selection rules in ΔB = 2 transition depend on the relative value of M (the mass scale that characterizes the ΔB = 2 interactions) and Λ_s (the super-symmetry-breaking scale). In particular, if M ? 10⁴GeV and Λ_s ～ 10²GeV, the effective ΔB = 2 interactions induce NN annihilation in a nucleus yielding two kaons in the final state while processes with only one or zero kaons are suppressed by mixing angles. On the other hand, if M ? 10⁴GeV, then supersymmetry does not imply any additional selection rules beyond those of ordinary (non-supersymmetric) theories.     

Four weak gauge boson production at photon linear collider and heavy Higgs signal

We study the signals and backgrounds for a heavy Higgs boson in the processes γγ → WWWW, γ → WWZZ at the proton linear collider. The results are based on the complete tree-level SM calculation for these reactions. We show that the invariant mass spectrum of central WW, ZZ pairs is sensitive to the signal from Higgs boson with a mass up to 1 TeV linear collider for integrated luminosity of 300 fb⁻¹. At 1.5 TeV PLC Higgs boson with a mass up to 700 GeV can be studied. The nonresonant longitudinal gauge boson scattering (m_H = ∞) can be detected in photon-photon collisions at e⁺e⁻ center-of-mass energy of 3 TeV.     

Electroweak one-loop corrections to the decay of the charged vector boson

The electroweak radiative corrections to the decay widths of theW-boson, Γ \((W \to l\bar v,\bar ud,\bar cs)\) , have been calculated in the standard theory. The results are presented in terms of an electroweak form factorρ ^W and their dependence onm _t , andM _H (masses oft-quark and higgs boson) is studied. Typically,ρ ^W ?1 is of an order of one percent. The differenceρ _lv ^W ?ρ _qq′ ^W is negligible, 0.046%. The calculational scheme used is described in detail.     

CP violation in decay rates of charged bottom mesons

In the standard theory we discuss a mechanism of interference between two different tree-level charged current amplitudes to induce CP violation. The asymmetry between conjugate Cabibbo disfavoured modes of charged bottom meson decays is considered. Estimates for two-body decays ofB _u andB _c are presented. We find thatB _u ^? →D ^?+D ₀ ^* , for instance, can give a big CP asymmetry with values ≈1–50%, depending on the angle and phase parameters.