共查询到20条相似文献,搜索用时 31 毫秒
1.
The cosmological effects of thermal masses of particles (masses induced via interactions at nonzero temperature) as well as ordinary masses are studied. These effects are shown to be negligible for photons. For electrons, however, they modify the dependence of the universe's radiusR and the timet on temperature. 相似文献
2.
Using the theoretical ambiguities inherent in the seesaw mechanism, we derive the new analytic expressions for both quadratic
and linear seesaw formulae for neutrino masses at low energies, with either up-type quark masses or charged lepton masses.
This is possible through full radiative corrections arising out of the renormalizations of the Yukawa couplings, the coefficients
of the neutrino-mass-operator in the standard model with two-Higgs doublets, and also the QCD-QED rescaling factors below
the top-quark mass scale, at one-loop level. We also investigate numerically the unification of top-b-τ Yukawa couplings at the scale M
1=0.59×108 GeV for a fixed value of tan β=58.77, and then evaluate the seesaw neutrino masses which are too large in magnitude to be compatible with the presently
available solar and atmospheric neutrino oscillation data. However, if we consider a higher but arbitrary value of M
1=0.59×1011 GeV, the predictions from linear seesaw formulae with charged lepton masses, can accommodate simultaneousely both solar atmospheric
neutrino oscillation data. 相似文献
3.
In this paper we prove that there are only two different classes of central configurations with convenient masses located at the vertices of two nested regular tetrahedra: either when one of the tetrahedra is a homothecy of the other one, or when one of the tetrahedra is a homothecy followed by a rotation of Euler angles α=γ=0 and β=π of the other one.We also analyze the central configurations with convenient masses located at the vertices of three nested regular tetrahedra when one them is a homothecy of the other one, and the third one is a homothecy followed by a rotation of Euler angles α=γ=0 and β=π of the other two.In all of these cases we have assumed that the masses on each tetrahedron are equal but masses on different tetrahedra could be different. 相似文献
4.
With the decay constants of D and D
s
mesons measured in experiment recently, we revisit the study of the bound states of quark and antiquark in B and D mesons in the relativistic potential model. The relativistic bound state wave equation is solved numerically. The masses,
decay constants and wave functions of B and D mesons are obtained. Both the masses and decay constants obtained here can be seen as consistent with the experimental data.
The wave functions can be used in the study of B and D meson decays. 相似文献
5.
In the supersymmetric standard model of particle interactions, R-parity nonconservation is often invoked to obtain nonzero neutrino masses. We point out here that such interactions of the supersymmetric particles would erase any pre-existing lepton or baryon asymmetry of the universe before the electroweak phase transition through the B+L violating sphaleron processes. We also point out that all models of radiative generation of neutrino masses suffer from the same problem. We then show how neutrino masses may be obtained in supersymmetry (assuming R-parity conservation) together with successful leptogenesis and predict the possible existence of new observable particles. 相似文献
6.
Amitava Datta Monoranjan Guchait Amitava Raychaudhuri 《Zeitschrift fur Physik C Particles and Fields》1992,54(3):513-517
The allowed regions in the chargino-gluino mass plane are mapped out using the latestZ decay data from experiments. The determination of these masses in future experiments will uniquely fix the neutralino mass spectrum for a fixedv
1/v
2. Since the usual two-fold ambiguity is removed by LEP data for gluino masses upto 200 GeV. Constraints have also been placed on neutralino masses. 相似文献
7.
Andrea Raspini 《International Journal of Theoretical Physics》1992,31(8):1407-1415
The masses of the ground-state light baryons are calculated in the quark model. The unperturbed wave functions correspond to a hyperspherical harmonic confinement. The perturbation includes a short-range potential and all the relevant relativistic corrections of the order ofv
2/c
2. Results are compared with the experimental values and found to be in good agreement. This may be a test not of the hyperspherical harmonic model so much as of the feasibility of a simple (but consistent) relativistically corrected fit of the light baryon masses. 相似文献
8.
The presence of domain walls separating regions of unbrokenSU(2)L andSU(2)R is shown to provide necessary conditions for leptogenesis which converts later to the observed baryon asymmetry. The strength
of lepton number violation is related to the Majorana neutrino mass and hence related to current bounds on light neutrino
masses. Thus the observed neutrino masses and the baryon asymmetry can be used to constrain the scale of left-right symmetry
breaking. 相似文献
9.
O. Buchmueller R. Cavanaugh A. De Roeck J. R. Ellis H. Flaecher S. Heinemeyer G. Isidori K. A. Olive F. J. Ronga G. Weiglein 《The European Physical Journal C - Particles and Fields》2009,64(3):391-415
On the basis of frequentist analyses of experimental constraints from electroweak precision data, (g−2)
μ
, B-physics and cosmological data, we investigate the parameters of the constrained MSSM (CMSSM) with universal soft supersymmetry-breaking
mass parameters, and a model with common non-universal Higgs masses (NUHM1). We present χ
2 likelihood functions for the masses of supersymmetric particles and Higgs bosons, as well as BR(b→s
γ), BR(B
s
→μ
+
μ
−) and the spin-independent dark-matter scattering cross section, σ
p
SI. In the CMSSM we find preferences for sparticle masses that are relatively light. In the NUHM1 the best-fit values for many
sparticle masses are even slightly smaller, but with greater uncertainties. The likelihood functions for most sparticle masses
are cut off sharply at small masses, in particular by the LEP Higgs mass constraint. Both in the CMSSM and the NUHM1, the
coannihilation region is favored over the focus-point region at about the 3-σ level, largely but not exclusively because of (g−2)
μ
. Many sparticle masses are highly correlated in both the CMSSM and NUHM1, and most of the regions preferred at the 95% C.L.
are accessible to early LHC running, though high-luminosity running would be needed to cover the regions allowed at the 3-σ levels. Some slepton and chargino/neutralino masses should be in reach at the ILC. The masses of the heavier Higgs bosons
should be accessible at the LHC and the ILC in portions of the preferred regions in the (M
A
,tan β) plane. In the CMSSM, the likelihood function for BR(B
s
→μ
+
μ
−) is peaked close to the Standard Model value, but much larger values are possible in the NUHM1. We find that values of σ
p
SI>10−10 pb are preferred in both the CMSSM and the NUHM1. We study the effects of dropping the (g−2)
μ
, BR(b→s
γ), Ω
χ
h
2 and M
h
constraints, demonstrating that they are not in tension with the other constraints. 相似文献
10.
We consider non-renormalizable interaction term as perturbation of the conventional neutrino mass matrix. We assume that the
neutrino masses and mixing arise through physics at a scale intermediate between Planck scale and the electroweak breaking
scale. We also assume that, just above the electroweak breaking scale, neutrino masses are nearly degenerate and their mixing
is tetra-maximal. Quantum gravity (Planck scale effects) lead to an effective SU(2)
L
×U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields. On electroweak symmetry breaking, this operator
gives rise to correction to the above masses and mixing. These additional term can be consider as a perturbation to the Tetra-maximal
mass matrix. The nature of gravitational interaction demands that the element of this perturbation matrix should be independent
of flavor indices. We compute the deviation of three neutrino mixing angles due to Planck scale effects. We find that there
is no change in θ
13 and θ
23 but change in solar mixing angle θ
12 is suppress by 3.0°. 相似文献
11.
Albino Hernández-Galeana William A. Ponce Arnulfo Zepeda 《Zeitschrift fur Physik C Particles and Fields》1992,55(3):423-434
Electroweak and horizontal interactions are unified with the groupSU(6)
L
U(1)
Y
for three generations. The horizontal gauge group suggested from low energy phenomenology isSU(2)
H
. This model does not contain exotic quarks, but exotic leptons are needed in order to make it anomaly-free. The breaking of the symmetry gives, in a natural way, heavy masses for exotic leptons and a BCS mass matrix for the up quarks, which implies that at tree level only the top quark gets a mass of orderM
W
. The see-saw mechanism generates tiny masses for the three known neutrinos. The remaining of the known fermion masses are light, because they can be generated only as radiative corrections. 相似文献
12.
We have constructed some Regge trajectories for mesons and baryons by taking the 70 MeV spinless mass quanta as the ultimate
building block for the light hadrons. In order to make masses integral multiples of seventy, small changes in masses has been
made with due explanation. We have shown how a linear relationship between J and M
2 is maintained by considering quantized hadron masses, which is a direct consequence of the string model and gives a strong
clue for quark confinement. It has also been established that mesons and baryons have different slopes and the slopes of baryons
is less than the slope of the mesons. This clearly defies the concept of universality of slopes (α ≈ 1.1 GeV2) of hadrons, which can only be achieved if the strings joining the quarks have constant string tension α = 1/(2πσ) (where σ is the string tension). 相似文献
13.
Sudhir K Vempati 《Pramana》2000,55(1-2):277-282
It has been known for sometime that supersymmetric theories with R-parity violation provide a natural framework where small neutrino masses can be generated. We discuss neutrino masses and
mixing in these theories in the presence of trilinear lepton number violating couplings. It will be shown that simultaneous
solutions to solar and atmospheric neutrino problems can be realized in these models. 相似文献
14.
Precisionmeasurements of Z-boson parameters andW-boson and t-quark masses put strong constraints on non SU(2) × U(1) singlet New Physics.We demonstrate that one extra generation passes electroweak constraints even when all new particle
masses are well above their direct mass bounds. 相似文献
15.
16.
The masses of the SU(3)×SU(6) hadrons are calculated in the chiral-invariant phase space (CHIPS) model as a sum of the mean energies of the quarks at
a constant temperature T
c with the color-magnetic splitting and the color-electric shift. The masses of hadrons are parametrized by four constants:
T
c, ms, E
CE and A
CM. With the same number of parameters the CHIPS model fits the masses of hadrons better than the classic bag model. The small
mass of the d-quark ( m
d = 2.7MeV) is used to prove that the isotopic shifts of hadrons can be explained by the mass difference between the d- and u-quarks. The dibaryon mass is estimated in CHIPS to be 200MeV higher than in the bag model. The prediction for the mass of the α* cluster is about the same in both models. It is close to 4 .
m
Δ.
Received: 12 December 2001 / Accepted: 23 May 2002 相似文献
17.
We analyse in detail the behaviour of supersymmetric QCD with a number of flavours M smaller than the number of colours N, for quark masses smaller than the dynamically generated scale Λ. In this regime, we find it useful to move from meson superfields to Nambu–Goldstone-like variables. In particular we work out the mass spectrum and the set of decay constants that specify the interactions of the low-energy theory. We explicitly check that masses and decay constants have a consistent behaviour under decoupling and that they satisfy current algebra requirements. Finally we speculate about the massless limit. For vanishing quark masses, and only in this case, the relation between mesons and Nambu–Goldstone variables becomes singular. When analysed in terms of the Nambu–Goldstone superfields, the massless limit exhibits a spontaneous breaking of the flavour symmetry, with massless Goldstone modes embedded in an M2-dimensional complex moduli space. The symmetry-breaking order parameter is formally infinite, but this has the only effect of turning off the interactions between the chiral superfields. The massive case, for masses smaller than Λ, can be thought of as a perturbation around the massless case, with corrections that can be systematically computed in the effective theory. 相似文献
18.
19.
Hans J. Fahr 《Foundations of Physics Letters》2006,19(5):423-440
According to ideas of Mach, Whitrow, Dirac, or Hoyle, inertial masses of particles should not be a genuine, predetermined
quantity; rather they should represent a relational quantity which by its value somehow reflects the deposition and constellation
of all other objects in their cosmic environment. In this paper we want to pick up suggestions given by Thirring and by Hoyle
of how, due to requirements of the equivalence of rotations and of general relativistic conformal scale invariance, the particle
masses of cosmic objects should vary with the cosmic length scale. We study cosmological consequences of comoving cosmic masses
which co-evolve by mass with the expansion of the universe. The vanishing of the covariant divergence of the cosmic energy-momentum
tensor under the new prerequisite that matter density only falls off with the reciproke of the squared cosmic scale S(t) then leads to the astonishing result that cosmic pressuredoes not fall off adiabatically but rather falls off in a quasi-isothermal
behaviour, varying with S(t) as matter density does. Hence, as a new cosmological fact, it arises that, even in the late phases of cosmic expansion,
pressure cannot be neglected what concerns its gravitational action on the cosmic dynamics. We then show that under these
conditions the cosmological equations can, however, only be solved if, in addition to matter, also pressure and energy density
of the cosmic vacuum are included in the calculation. An unaccelerated expansion with a Hubble parameter falling off with
S(t)−1 is obtained for a vacuum energy density decay according to S(t)−2 with a well-tuned proportion of matter and vacuum pressures. As it appears from these results, a universe with particle masses
increasing with the cosmic sale S(t) is in fact physically conceivable in an energetically consistent manner, if vacuum energy at the expansion of the universe
is converted into mass density of real matter with no net energy loss occuring. This universe in addition also happens to
be an economical one which has and keeps a vanishing total energy. 相似文献
20.
We study the divergent behavior ofW gravity theories. As a tool, we use the Grothendieck-Riemann-Roch theorem on the compactified moduli space. We show thatW
n
gravity has severe divergences caused by negative masses. However, for superextension ofW
n
gravity the divergences by negative masses are miraculously cured by the counterpart contribution of superpartners. 相似文献