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1.
Lepton-quark mass may reflect a correspondence in spacetime structure described by a modular conformal scaling group. Stemming in part from a spacetime line element correspondenceds → (expλ n)ds in which the eight quantitiesλ 0,λ 1, ...,λ 7 constitute a closed set under a modular addition, the associated formula for lepton-quark mass (yielding values at the 1 GeV scale for the leptons and lighter quarks and at the physical pole for the top) is conjectured to bem=m fQ2(exp −λ n), wherem f=10.245 TeV is the progenitor fermion mass,Q is the charge number of the lepton or quark, and the modular group parameterλ n is indexed by a fermion principal quantum numbern that depends on three mutually independent projection operators.  相似文献   

2.
A measurement of the 2S Lamb shift in muonic hydrogen (μp) is being prepared at the Paul Scherrer Institute (PSI). The goal of the experiment is to measure the energy difference ΔE(25 P 3/2−23 S 1/2) by laser spectroscopy (λ≈6μm) to a precision of 30 ppm and to deduce the root mean square (rms) proton charge radius with 10−3 relative accuracy, 20 times more precise than presently known. An important prerequisite to this experiment is the availability of long-lived μp2S -atoms. A 2S-lifetime of ∼1 μs – sufficiently long to perform the laser experiment – at H2 gas pressures of 1–2 hPa was deduced from recent measurements of the collisional 2S-quenching rate. A new low-energy negative muon beam yields an order of magnitude more muon stops in a small low-density gas volume than a conventional cloud muon beam. A stack of ultra-thin carbon foils is the key element of a fast detector for keV-muons. The development of a 2 keV X-ray detector and a 3-stage laser system providing 0.5 mJ laser pulses at 6 μm is on the way. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

3.
From a number of qualitative conjectures, the constantsm e ,c, , and a spin(8) gauge field theory, I derive the following particle masses (quark masses are constituent masses) and force constants: up quark mass=312.7542 MeV; down quark mass=312.7542 MeV; proton mass=938.2626 MeV; neutrino masses (all types)=0; muon mass=104.76 MeV; strange quark mass=523 MeV; charmed quark mass=1989 MeV; tauon mass=1877 MeV; bottom quark mass=5631 MeV; top quark mass=129.5 GeV;W + mass=80.87 GeV;W mass=80.87 GeV;W 0 mass=99.04 GeV; fine structure constant= 1/137.036082; weak constant times the proton mass squared M p 2 =0.97×10–5; color constant=0.6286. From the pion mass in addition, I derive the Planck mass (1–1.6)×1019 GeV, so that the gravitational constant times the proton mass squared GM p 2 (3.6–8.8)×10–39.  相似文献   

4.
New experimental data on the binding energyB λλ ofλλ6He, reported very recently, come up with the valuesB λλ = 725 ±0.14 MeV and ΔBλλ = 101 ±0.2 MeV which are substantially lower than the old dataB λλ = 109 ±0.8 MeV and ΔBλλ = 4.7±10 MeV in use in literature since 1966. In view of the new data we decided to undertake a re-study of the λλ 6 He hypernucleus using the same three-body model (α-λ-λ) with a simple coordinate space variational approach which was employed earlier with the old data onλλ/6He. After fitting different λ-λ potentials to the new data of λλ 6 He we have applied our method to study some double-λ hypernuclei in light, medium and heavy mass regions and have determined the structural quantities like Bλλ, the r.m.s. values of core-λ (〈rcore-λ〉〉) and λ-λ (〈rλ-λ〉〉) distances theoretically. The core-λ interaction considered is of Woods-Saxon type. The strength and the range of the core-A potential have been adjusted to reproduce the λ-binding energy(B λ) . These are in good agreement with the relativistic mean field (RMF) results. Our study shows that the λ-λ bonding energy ΔBλλ decreases with increasing mass number from λλ 10 Be to λλ 210 Pb of a double-A hypernucleus  相似文献   

5.
Using light-front dynamics, and the notion of the running effective quark mass, we propose a model of the three-quark nucleon wave function, which accounts simultaneously both for the low and the high energy experimental data. Our wave function is a product of a spinor part, inferred from the QCD sum rules, and a gaussian scalar factor, taken for simplicity. Including all three Ioffe currents we get from one wave function both the negative neutron charge radius 〈r2neutron=-0.108 fm2 and the decreasing d/u ratio in the proton for xBj increasing from 0.5 to 1.  相似文献   

6.
The charged π-meson and proton mixed hadronic jets in the fragmentation regions of π + p and π + C interactions at 40 GeV/c are extracted and their properties are investigated. It has been shown that the characteristics of the jets in the π-meson fragmentation region are universal in jet events, do not depend on the type of the target and are defined only from the quark contents of the π meson. The jet characteristics in the proton fragmentation region are different and depend upon the quark contents of the proton. Mixed hadronic jets with defined values of the electric charge were studied. The resonance structures related to the Δ isobars are discovered in the effective mass distributions of the jets. It has been shown that the small azimuthal angle high-p T correlations are observed and strong back-to-back correlations exist. The text was submitted by the authors in English.  相似文献   

7.
A number of peculiarities were found in the effective mass spectrum of the ΛK S 0 system in the ranges of 1650–1680, 1740–1750, 1785–1805, 1835–1860, and 1925–1950 MeV/c 2 during the collision of a 10-GeV/c 2 momentum proton with propane. Detailed research of a mass spectrum structure has shown that significant enhancements have been obtained in two effective mass ranges of 1750 and 1795 MeV/c 2. These peaks could be interpreted as possible candidates of two pentaquark states: the N 0 with quark content udsds decaying into ΛK 0 and the Ξ0 resonance with quark content udsds decaying into . The text was submitted by the authors in English.  相似文献   

8.
Segar  J  Sriram  M S 《Pramana》1989,32(3):181-193
We consider a quark model based on QCD scale anomaly in which the quarks move in the field of an effective glueball field. Hadrons correspond to solitonic bags of higher energy density in a nonperturbative sea of condensed gluons. We calculate the static properties of nucleon in this model and find that the nucleon mass is far too large (2.4–4 GeV) and the proton charge radius (0.37–0.54 fm) is low. The proton gyromagnetic ratio and gA/gv are in reasonable agreement with the experimental numbers.  相似文献   

9.
In this paper, U(3)L×U(3)R chiral theory of mesons is extended to the leading order in quark mass expansion in order to evaluate the ρ0-ω mixing. It is shown that the use of path integral method to integrate out the quark fields naturally leads to the ρ0-ω mixing vertices, and this mixing is entirely from the quark loop in this theory. The off-shell behaviour of the mixing amplitude is analyzed. The on-shell mixing amplitude is obtained from the decay ω→π+π. Furthermore, the constraints on the light quark mass parameters are extracted from the ρ0-ω mixing and the mesons masses, and the mass splitting of K*(892)-mesons is predicted. Received: 30 January 1998 / Revised version: 3 June 1998  相似文献   

10.
Chiral constituent quark model with configuration mixing (χCQMconfig) is known to provide a satisfactory explanation of the “proton spin problem” and related issues. In order to enlarge the scope of χCQMconfig, we have attempted to phenomenologically incorporate x-dependence in the quark distribution functions. In particular, apart from calculating valence and sea quark distributions qval(x) and q̄(x), we have carried out a detailed analysis to estimate the sea quark asymmetries d̄(x)-ū(x), d̄(x)/ū(x) and as well as spin independent structure functions F2 p(x)-F2 n(x) and F2 n(x)/F2 p(x) as functions of x. We are able to achieve a satisfactory fit for all the above mentioned quantities simultaneously. The inclusion of effects due to configuration mixing have also been examined in the case F2 p(x)-F2 n(x) and F2 n(x)/F2 p(x) where the valence quark distributions dominate and it is found that it leads to considerable improvement in the results. Further, the valence quark structure has also be tested by extrapolating the predictions of our model in the limit x→1 where data is not available.  相似文献   

11.
In this article we intend to discuss the evolution of polarized and unpolarized structure functions in the (x,Q2) plane. We analyze the proton data on the spin dependence asymmetry A1(x,Q2), by making the dynamical assumption that at low resolution energies, the hadrons consist only of valence quarks and the scaling violation of F2(x,Q2) at low x comes only from the gluons density. While the sea quark and the gluon distributions are calculated using the inverse Mellin technique and the various moments of the valence quarks, the valence quark distribution itself is obtained from the relativistic quark-exchange model. A comparison is made with the corresponding available experimental data. Finally in agreement with the data, it is demonstrated that there is no significant Q2-dependence of asymmetry A1(x,Q2) for x ranging 0.014 ≤ x ≤ 0.25. Received: 11 September 1999 / Revised version: 8 December 1999  相似文献   

12.
Without Higgs field interaction, accurate pole mass values are obtained for the charged leptons and quarks from a Z3-symmetric linear superposition self-interference of the Dirac fields in the effective free-field Lagrangian. The charged lepton and quark pole masses evidence the discrete Z3 symmetry, the theoretical-experimental deviations δm/m are $ \mathcal{O} $ \mathcal{O} (10−5) for all three charged leptons, and the quark pole masses are in very satisfactory overall agreement with the experimental data.  相似文献   

13.
Properties of the lowest 0+ states of 12C are calculated to study the role of three-body interactions in the α-cluster model. An additional short-range part of the local three-body potential is introduced to incorporate the effects beyond the α-cluster model. There is enough freedom in this potential to reproduce the experimental values of the ground-state and excited-state energies and the ground-state root-mean-square radius. The calculations reveal two principal choices of the two-body and three-body potentials. Firstly, one can adjust the potentials to obtain the width of the excited 02+ state and the monopole 02+↦01+ transition matrix element in good agreement with the experimental data. In this case, the three-body potential has strong short-range attraction supporting a narrow resonance above the 02+ state, the excited-state wave function contains a significant short-range component, and the excited-state root-mean-square radius is comparable to that of the ground state. Next, rejecting the solutions with an additional narrow resonance, one finds that the excited-state width and the monopole transition matrix element are insensitive to the choice of the potentials and both values exceed the experimental ones.  相似文献   

14.
We present an application of continuous-wave (cw) cavity-enhanced absorption spectroscopy (CEAS) with off-axis alignment geometry of the cavity and with time integration of the cavity output intensity for detection of narrow-band and broadband absorbers using single-mode red diode lasers at λ=687.1 nm and λ=662 nm, respectively. Off-axis cw CEAS was applied to kinetic studies of the nitrate radical using a broadband absorption line at λ=662 nm. A rate constant for the reaction between the nitrate radical and E-but-2-eneof (3.78±0.17)×10-13 cm3 molecule-1 s-1 was measured using a discharge-flow system. A nitrate-radical noise-equivalent (1σ≡ root-mean-square variation of the signal) detection sensitivity of 5.5×109 molecule cm-3 was achieved in a flow tube with a diameter of 4 cm and for a mirror reflectivity of ∼99.9% and a lock-in amplifier time constant of 3 s. In this case, a noise-equivalent fractional absorption per one optical pass of 1.6×10-6 was demonstrated at a detection bandwidth of 1 Hz. A wavelength-modulation technique (modulation frequency of 10 kHz) in conjunction with off-axis cw CEAS has also been used for recording 1f- and 2f-harmonic spectra of the RR(15) absorption of the b1Σg +-X3Σg - (1,0) band of molecular oxygen at =14553.947 cm-1. Noise-equivalent fractional absorptions per one optical pass of 1.35×10-5, 6.9×10-7 and 1.9×10-6 were obtained for direct detection of the time-integrated cavity output intensity, 1f- and 2f-harmonic detection, respectively, with a mirror reflectivity of ∼99.8%, a cavity length of 0.22 m and a detection bandwidth of 1 Hz. Received: 24 June 2002 / Revised version: 12 August 2002 / Published online: 15 November 2002 RID="*" ID="*"Corresponding author. Fax: +44-1865/275410, E-mail: vlk@physchem.ox.ac.uk  相似文献   

15.
The electric form factor of the c [`(\texts)] \overline {\text{s}} uū tetraquark with JPC = 0++ (M = 2691 MeV) in the field of a small and intermediate momentum transfer Q2 ≤ 1 GeV2 is calculated for the relativistic quark model. The charge radius of this state is determined.  相似文献   

16.
The question how the spin of the nucleon is distributed among its quark and gluon constituents is still a subject of intense investigations. Lattice QCD has progressed to provide information about spin fractions and orbital angular momentum contributions for up and down quarks in the proton, at a typical scale m2 \mu^{2}_{} ∼ 4 GeV2 . On the other hand, chiral quark models have traditionally been used for orientation at low momentum scales. In the comparison of such model calculations with experiment or lattice QCD, fixing the model scale and the treatment of scale evolution are essential. In this paper, we present a refined model calculation and a QCD evolution of lattice results up to next-to-next-to-leading order. We compare this approach with the Myhrer-Thomas scenario for resolving the proton spin puzzle.  相似文献   

17.
On the basis of the experimental data on diffractive processes in πp, pp and pˉp collisions at intermediate, moderately high and high energies, we restore the scattering amplitude related to the t-channel exchange by vacuum quantum numbers by taking account of the diffractive s-channel rescatterings. At intermediate and moderately high energies, the t-channel exchange amplitude turns, with a good accuracy, into an effective pomeron which renders the results of the additive quark model. At superhigh energies the scattering amplitude provides a Froissart-type behaviour, with an asymptotic universality of cross sections such as σtot πptot pp→ 1 at s→∞. The quark structure of hadrons being taken into account at the level of constituent quarks, the cross sections of pion and proton (antiproton) in the impact parameter space of quarks, σπ(r 1⊥, r 2⊥; s) and σp(r 1⊥, r 2⊥, r 3⊥; s), are found as functions of s. These cross sections implicate the phenomenon of colour screening: they tend to zero at |r i⊥r k⊥|→ 0. The effective colour screening radius for pion (proton) is found for different s. The predictions for the diffractive cross sections at superhigh energies are presented. Received: 15 December 1998  相似文献   

18.
We present an application of cavity-enhanced absorption spectroscopy with an off-axis alignment of the cavity formed by two spherical mirrors and with time integration of the cavity-output intensity for detection of nitrogen dioxide (NO2) and iodine monoxide (IO) radicals using a violet laser diode at λ=404.278 nm. A noise-equivalent (1σ≡ root-mean-square variation of the signal) fractional absorption for one optical pass of 4.5×10-8 was demonstrated with a mirror reflectivity of ∼0.99925, a cavity length of 0.22 m and a lock-in-amplifier time constant of 3 s. Noise-equivalent detection sensitivities towards nitrogen dioxide of 1.8×1010 molecule cm-3 and towards the IO radical of 3.3×109 molecule cm-3 were achieved in flow tubes with an inner diameter of 4 cm for a lock-in-amplifier time constant of 3 s. Alkyl peroxy radicals were detected using chemical titration with excess nitric oxide (RO2+NO→RO+NO2). Measurement of oxygen-atom concentrations was accomplished by determining the depletion of NO2 in the reaction NO2+O→NO+O2. Noise-equivalent concentrations of alkyl peroxy radicals and oxygen atoms were 3×1010 molecule cm-3 in the discharge-flow-tube experiments. Received: 4 February 2003 / Revised version: 10 March 2003 / Published online: 12 May 2003 RID="*" ID="*"Corresponding author. Fax: +44-1865/275-410, E-mail: vlk@physchem.ox.ac.uk  相似文献   

19.
Stress-induced crystallisation (SIC) and stress-induced melting (SIM) in natural rubbers (NR), unfilled and filled with carbon black (CB) have been studied by 2H-NMR measurements. Various materials have been swollen with small amount (< 2%) of deuterated alkane chains. The orientation of the amorphous chains, then the local deformation of the amorphous chains during deformation cycles and during stress relaxation, permits to clarify the SIC and SIM processes during hardening and recovery. By mechanical, WAXS and NMR measurements one determines the same critical draw ratio for appearance λA and disappearance λE of the crystallites. It is demonstrated that the hysteresis observed by the different techniques (stress σ, crystallinity χ, NMR splitting Δν) are due to the supercooling effect ( λA > λE, at constant temperature). During hardening at constant strain rate it is found that the local draw ratio remains constant and equal to λA, whereas the crystallinity increases linearly with the macroscopic draw ratio λ. The hardening σ ∼ (λ - λA)2 is then interpreted as a reinforcement effect due to the crystallites, which act as new crosslinks. This confirms the prediction of Flory. In filled rubber the same effects are observed, and the stress amplification factor is determined as a function of the CB content. It is found that the fillers act as nucleation centres for the NR crystallites. The reinforcement of such materials is due principally to this nucleation effect and to the presence of a super network formed by both the NR crystallites and the CB fillers.  相似文献   

20.
An experimental analysis is presented to correlate the secondary dendrite arm spacing λ 2 and dendrite tip radius R with growth rate V and Mg content C 0-Mg of Al–Cu–Mg ternary alloys. Under constant temperature gradient G (4.84±0.13 K mm−1), a series of directional solidification experiments were performed at five different growth rates V (16.7–83.3 μm/s) and five different Mg contents C 0-Mg in Al–5 wt.% Cu–(0.5–5) wt.% Mg alloys. Solid–liquid interface was investigated from the longitudinal sections of the quenched samples, and λ 2 and R were measured on the dendrite tips. The dependencies of λ 2 and R on V and C 0-Mg were determined. The experimental results showed that the values of λ 2 and R decrease as V and C 0-Mg increase at a constant G. The present exponent values related to V are found to be slightly lower than the values of the theoretical models and previous experimental works; however, C 0-Mg exponent values are found to be much lower than the theoretical models and previous experimental works. The ratio of the secondary dendrite arm spacing to the dendrite tip radius is 2.09±0.15, in good agreement with the scaling law. At a constant C 0-Mg, the values of VR 2 were found to slightly increase with the ascending V. However, as C 0-Mg increases, the values of VR 2 decrease.  相似文献   

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