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1.
The explicit canonical structure of the light cone restriction of the commutator of the weak current with its divergence is considered in the interacting quark-gluon model quantized in the finite momentum frame. The implications on neutrino scattering are analyzed. W4 and W5 are predicted to scale nontrivially as ν−2F4( ω) and ν−2F5( ω), which provides a simple test of light cone current algebra feasible in the near future. The Σ-term for weak currents is deduced from a casual representation near the light cone, and a correction is also made in the W5-sum rule obtained by naive infinite momentum techniques. 相似文献
2.
We derive new QCD sum rules for B→ D and B→ D
* form factors. The underlying correlation functions are expanded near the light-cone in terms of B-meson distribution amplitudes defined in HQET, whereas the c-quark mass is kept finite. The leading-order contributions of two- and three-particle distribution amplitudes are taken into
account. From the resulting light-cone sum rules we calculate all B→ D
(*) form factors in the region of small momentum transfer (maximal recoil). In the infinite heavy-quark mass limit the sum rules
reduce to a single expression for the Isgur–Wise function. We compare our predictions with the form factors extracted from
experimental B→ (*)
l
ν
l
decay rates fitted to dispersive parameterizations. 相似文献
3.
We analyze the higher-twist effects and the SU(3)-flavor symmetry breaking in the correlation functions used to calculate form factors of pseudoscalar mesons in the QCD
light-cone sum rule approach. It is shown that the Ward identities for these correlation functions yield relations between
twist-4 two- and three-particle distribution amplitudes. In addition to the relations already obtained from the QCD equations
of motions, we have found a new one. With the help of these relations, the twist-4 contribution to the light-cone sum rule
for the pion electromagnetic form factor is reduced to a very simple form. Simultaneously, we correct a sign error in an earlier
calculation. The updated light-cone sum rule prediction for the pion form factor at intermediate momentum transfers is compared
with the recent Jefferson Lab data. Furthermore, from the correlation functions with strange-quark currents the kaon electromagnetic
form factor and the weak transition form factors are predicted with accuracy.
Received: 30 June 2002 / Published online: 7 October 2002
RID="a" 相似文献
4.
Nucleon structure functions obtained from neutrino and anti-neutrino scattering on iron nuclei at high energies ( E v =30 to 250 GeV) are presented. These results are compared with the results of other lepton-nucleon scattering experiments. The structure functions are used to test the validity of the Gross-Llewellyn-smith sum rule, which measures the number of valence quarks in the nucleons, and to obtain leading and second order QCD fits. 相似文献
5.
Sum rules for the S-wave amplitudes of the nonleptonic hyperon decays are discussed. A new sum rule √12( Λ00 + Ξ00) = (∑ ?? ? ∑ ++) is proposed as one of the comprehensive sum rules in the SU(4) symmetry theory. 相似文献
6.
The transverse momenta of charged hadrons produced in high energy muon-proton scattering have been studied. The average squared transverse momentum 〈 p2⊥〉 shows a strong dependence on z = Eh/ v characteristic of intrinsic momentum effects and a significant rise as a function of s = W2. The W2, q2, x and z dependences of the data are compared with the predictions of a perturbative QCD model. 相似文献
7.
We build a simple Standard Model extension based on T7 flavor symmetry which accommodates lepton mass, mixing with non-zero θ13, and CP violation phase. The lepton mixing matrix is obtained from three triplets and one singlet under T7 symmetry, and the charged-lepton mass is derived through the spontaneous symmetry breaking by just one T7 triplet (φ), while neutrinos get small masses from one SU(2) L doublet and two SU(2)L singlets in which one is in 1 and the two others are in 3 and 3* under T7, respectively. There exist viable parameters of the model that predict the effective Majorana neutrino mass with values mβ ≃ 10−2 eV and 4.95 × 10−2 eV as well as a lightest neutrino mass mlight ≃ 4.97 × 10−3 eV and 1.61 × 10−3 eV for the normal and inverted neutrino mass hierarchies, respectively. The model also gives a remarkable prediction of Dirac CP violation δCP ≃ 303.3° in the normal hierarchy and δCP ≃ 56.69° in the inverted hierarchy which is still missing in the neutrino mixing matrix. The quark mixing angles of the model are closed to the experimental data, whereas the obtained values for the quark masses are consistent with with the experimental data at the tree level. 相似文献
9.
Quasielastic muon-neutrino scattering on nuclei of propane-Freon mixture at energies in the range E v < 1 GeV is studied. The multiplicity, momentum, and emission-angle distributions of final protons are measured along with the dependence of the mean values for these distributions on the neutrino energy in the range 0.2 < E v < 1 GeV. 相似文献
10.
We show that maximal atmospheric and large solar neutrino mixing can be implemented in SU(5) gauge theories, by making use of the U(1)
F
symmetry associated with a suitably defined family number F, together with a Z 2 symmetry which does not commute with F. U(1)
F
is softly broken by the mass terms of the right-handed neutrino singlets, which are responsible for the seesaw mechanism;
in additio
n, U(1)
F
is also spontaneously broken at the electroweak scale. In our scenario, lepton mixing stems exclusively from the right-handed-neutrino
Majorana mass matrix, whereas the CKM matrix originates solely in the up-type-quark sector. We show that, despite the non-supersymmetric
character of our model, unification of the gauge couplings can be achieved at a scale 10 16 GeV < m
U
< 10 19 GeV; indeed, we have found a particula
r solution to this problem which yields results almost identical to the ones of the minimal supersymmetric standard model.
Received: 29 November 2002 / Published online: 3 March 2003
RID="a"
ID="a" e-mail: walter.grimus@univie.ac.at
RID="b"
ID="b" e-mail: balio@cfif.ist.utl.pt 相似文献
12.
We show that a five-dimensional Universal Extra Dimension model, compactified on a line segment, is consistently formulated
even when the gauge symmetry is broken solely by non-zero Dirichlet boundary conditions on a bulk Higgs field, without any
quartic interaction. We find that the longitudinal W
+
W
− elastic scattering amplitude, under the absence of the Higgs zero mode, is unitarized by exchange of infinite towers of KK
Higgs bosons. Resultant amplitude scales linearly with the scattering energy μ ? s\propto\sqrt{s}, exhibiting five-dimensional nature. A tree-level partial-wave unitarity condition is satisfied up to 6.7 (5.7) TeV for the
KK scale m
KK=430 (500) GeV, favored by the electroweak data within 90% CL. 相似文献
14.
Existence of a purely leptonic neutral current weak interaction may permit the use of ν ω, e ? elastic scattering to limit the muon neutrino mass. 相似文献
15.
Using the general formulation for obtaining chemical potential μ of an ideal Fermi gas of particles at temperature T, with particle rest mass m 0 and average density 〈 N〉/ V, the dependence of the mean square number fluctuation 〈Δ N
2〉/ V on the particle mass m 0 has been calculated explicitly. The numerical calculations are exact in all cases whether rest mass energy m
0c 2 is very large (non-relativistic case), very small (ultra-relativistic case) or of the same order as the thermal energy k BT. Application of our results to the detection of the universal very low energy cosmic neutrino background (CNB), from any
of the three species of neutrinos, shows that it is possible to estimate the neutrino mass of these species if from approximate
experimental measurements of their momentum distribution one can extract, someday, not only the density 〈 N
v〉/ V but also the mean square fluctuation 〈Δ
v
2
〉/ V. If at the present epoch, the universe is expanding much faster than thermalization rate for CNB, it is shown that our analysis
leads to a scaled neutrino mass m
v
instead of the actual mass m
0v
. 相似文献
16.
We discuss the concept of Schwinger, which starts with the hypothesis of the existence of magnetical monopoles and results in a baryon model with magnetically charged constituents. Especially we analyse the mathematical consistency of such a theory. which admits a connection between some magnetically charged “quarks” and the homogeneous Maxwell-equations ? v* Fμv( xu) = 0, which, displaying a lack of symmetry with respect to the inhomogeneous one, ? vFμv( xu) = 4? jμ, are replaced by ?* jμv. Here * jμ( xμ) means a conserved magnetic current which provides a monopole source for the magnetic field. 相似文献
17.
With the standard model gauge group and the three standard left-handed Weyl neutrinos, two minimal scenarios are investigated where an arbitrary non-Abelian lepton flavour symmetry group G
H
is responsible for a light neutrino with a large magnetic moment. In the first case, with scalar fields carrying lepton flavour, some finetuning is necessary to get a small enough neutrino mass for
v
= O(10) –11
B. In the second scenario, the introduction of heavy charged gauge singlet fermions with lepton flavour allows for a strictly massless neutrino to one-loop order. In both cases, the interference mechanism for small m
and large
v
is unique, independently of G
H
. In explicit realizations of the two scenarios, the horizontal groups are found to be non-Abelian extensions of a Zeldovich-Konopinski-Mahmoud lepton number symmetry. Only a discrete part of G
H
is spontaneously broken leading to a light Dirac neutrino with a large magnetic moment. 相似文献
18.
The energy spectrum of photons emitted in neutrino (antineutrino) scattering on electrons at E v ? m v is calculated with the assumption that the neutral electron flow has an arbitrary (V, A) structure. The result obtained is generalized to the case of possible neutrino oscillations, \(v_e \begin{array}{*{20}c} { - \to } \\ { \leftarrow - } \\ \end{array} v_\mu , \overline v _e \begin{array}{*{20}c} { - \to } \\ { \leftarrow - } \\ \end{array} \overline v _\mu \) , at an arbitrary neutrino mixing angle. Using the Weinberg-Salam model (sin 2θ W = 0.23) estimates of the sections dσ γ/dω and σ γ are obtained with consideration of the reactor antineutrino flux \(\bar v_e \) . The contributions from charged and neutral lepton fluxes and their interference to dσ γ/dω are compared. 相似文献
19.
The neutrino-electron scattering in a dense degenerate magnetized plasma under the conditions μ
2 > 2 eB ≫ μE is investigated. The volume density of the neutrino energy and momentum losses due to this process are calculated. The results
we have obtained demonstrate that plasma in the presence of an external magnetic field is more transparent for neutrino than
for non-magnetized plasma. It is shown that neutrino scattering under conditions considered does not lead to the neutrino
force acting on plasma. 相似文献
20.
A search for decays of heavy neutrinos was conducted by the CHARM Collaboration in a prompt neutrino beam produced by dumping 400 GeV protons in a Cu target, and in the CERN wide-band neutrino beam produced by 400 GeV primary protons. No candidate event was found. In the beam-dump experiment heavy neutrinos have been assumed to be produced by mixing in charmed D meson decays. Neutrinos decaying into e +e−ve, μ+e−vμ, and μ+μ−vμ were searched for. Limits of | Uei| 2, | Uμi| 2 < 10 −7 were obtained for neutrino masses around 1.5 GeV. In the wide-band experiment heavy neutrinos were assumed to be produced by neutral-current neutrino interactions in the CHARM calorimeter. Here a search was made for neutrinos decaying into a μ and hadrons. This experiment is sensitive to decays of neutrinos with mass in the range 0.5–2.8 GeV with limits of | Uμi| 2 < 3 × 10 −4 for masses around 2.5 GeV. These measurements extend our previous results in the mass range 10–400 MeV. 相似文献
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