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1.
We assess the theoretical uncertainties on the total charm cross section. We discuss the importance of the quark mass, the scale choice and the parton densities on the estimate of the uncertainty. We conclude that due to the small charm quark mass, which amplifies the effect of varying the other parameters in the calculation, the uncertainty on the total charm cross section is difficult to quantify.  相似文献   

2.
A multiperipheral model is suggested, in which the dependence of the amplitude of production of “n” particles on pair energy and existence of many particles exchanged (?, ω, π, A2, f) is taken into account.  相似文献   

3.
The total hadronic cross section, σT has been measured for tagged γ-rays, using electron beams in the GeV range, and narrow energy bins. Preliminary data are given covering the γ-energy region 275 MeV-1850 MeV, where interesting structure characteristics are observed.  相似文献   

4.
We discuss the energy dependence of the total charm cross section and some of its theoretical uncertainties including the quark mass, scale choice and the parton densities.  相似文献   

5.
The empirical equality of B2σt is noted, for the pomeron terms in NN, πN, KN, ?N, ωN, and φN scattering, where B is the elastic slope parameter and σt is the total cross section. This ratio increases slowly with energy, but remains the same in all channels. This is equivalent to a relation between the diffractive interaction radii and opacities; the opacity scales with the square of the radius. We conjecture that this systematics extends to ψN scattering. We contrast B2σt universaility with the slope predictions of an f-coupled pomeron model. Some other predictions of the f-dominance hypothesis are tested against data.  相似文献   

6.
7.
New results for the neutron total cross section for tritium extrapolate to 1.70 ± 0.03 b at zero energy. With a theoretical constraint A1/A0=0.92 ± 0.04, the scattering lengths A1=3.60 ± 0.10, A0 = 3.91 ± 0.12, and Ac=3.68 ± 0.05 fm can be inferred independently of, but consistently with, the previous experimental value for the coherent length Ac=3.82 ± 0.24 fm.  相似文献   

8.
Total relative and absolute cross sections for He4-He4 have been measured between 110 and 1100 m/s velocity of the primary beam at scattering chamber temperatures of 5.0 and 77 K. Our measurements are sensitive to the low energy repulsive and the attractive part of the potential. The resulting potential is able to describe scattering measurements of other authors; it is also in very good agreement with ab initio calculations of Bertoncini and Wahl.  相似文献   

9.
Proton-nucleus total inelastic cross sections have been calculated in the multiple scattering theory for incident proton energies ranging between 20 and 105 GeV. The results are compared to available cosmic-ray data. In view of the present analysis, extrapolations of the latest I.S.R. results on the proton-proton total cross section σ according to a logarithmic law almost saturating the Froissart bound seem hazardous.  相似文献   

10.
We assess the theoretical uncertainties on the total heavy-quark cross section. We discuss the importance of the quark mass, the choice of the scale, the number of light flavors and the parton densities on the estimate of the uncertainty. At first glance, the uncertainty bands on the total charm cross sections obtained by integrating the FONLL inclusive cross section and by integrating the partonic total cross sections appear to be incompatible. We explain how this apparent difference arises and describe how the two results can be reconciled. The small mass of the charm quark amplifies the effect of varying the other parameters in the calculation, making the uncertainty on the total charm cross section difficult to quantify. On the other hand, the bottom-quark total cross section is under much better theoretical control, and differences between the two approaches are small.  相似文献   

11.
The question of the scale of the ππ total cross section is considered. We first give a simple intuitive argument for expecting cross sections in the massless chiral world to be finite. Assuming the universality of P-f Regge couplings, we give a simple dispersion theoretic evaluation of the asymptotic ππ total cross section, σππ. We deduce an algebraic expression for σππ and find that its scale is determined by 1/m?2 or, equivalently, 1/fπ2 — just as Pagels conjectured. This relation has a smooth, finite limit as mπ tends to zero. Numerically, we obtain σππ = 17 ± 4mb for physical mass pions and 14 ± 3mb for massless pions.  相似文献   

12.
The total cross section for the reaction ep → enπ+ at momentum transfers |k2| between 0.08 and 0.32 (GeVc)2 and for centre of mass energies between threshold, at W = 1.078 GeV, and W = 1.106 GeV has been measured by detecting the electron and neutron in coincidence. Comparisons are made with both current algebra and dispersion relation theoretical models.  相似文献   

13.
The origin of the rise of p-p total cross section (σt(pp)) is investigated by making use of the inclusive sum rule. The contribution to the rise of σt(pp) from the development of sharp peak near the kinematical boundary in the process p+p→p+ “anything” is almost completely canceled out by the decrease of the cross section in other x-region between s=45 (GeV/c)2 and s=2820 (GeV/c)2. Then the net contribution to the rise of σt(pp) from the process p+p→p+ “anything” is very likely to be zero. The true origin of the rise of σt(pp) is found to be the increase of inclusive cross sections at x ? 0 between PS and ISR energies. The contribution from the process p+p→π+ “anything” at x ? 0 to the rise of σt(pp) is estimated to be 3.2 mb, that from the process p+p→K + “anything”, 0.71 mb and that from the process p+p→p “anything”, 0.62 mb. According to our conclusion we expect that all total cross sections will rise with energy at high energy.  相似文献   

14.
15.
We demonstrate here that the correction to the total cross section of scattering from the deuteron (nucleus) considered by West is in fact equal to zero if NN? pairs in the deuteron wave function are neglected in a consistent way.  相似文献   

16.
17.
For the \(\bar pp\) and pp systems, we have used all of the extensive data of the Particle Data Group [K. Hagiwara et al. (Particle Data Group), Phys. Rev. D 66, 010001 (2002)]. We then subject these data to a screening process, the “Sieve” algorithm [M. M. Block, physics/0506010], in order to eliminate “ outliers” that can skew a χ2 fit. With the “Sieve” algorithm, a robust fit using a Lorentzian distribution is first made to all of the data to sieve out abnormally high Δχ i 2 , the individual ith point’s contribution to the total χ2. The χ2 fits are then made to the sieved data. We demonstrate that we cleanly discriminate between asymptotic ln s and ln2 s behavior of total hadronic cross sections when we require that these amplitudes also describe, on average, low energy data dominated by resonances. We simultaneously fit real analytic amplitudes to the “sieved” high energy measurements of \(\bar pp\) and pp total cross sections and ρ-values for \(\sqrt s \) ≥ GeV, while requiring that their asymptotic fits smoothly join the the σ pp and σpp total cross sections at \(\sqrt s \) = 4.0 GeV—again both in magnitude and slope. Our results strongly favor a high energy ln2 s fit, basically excluding a ln s fit. Finally, we make a screened Glauber fit for the p-air cross section, using as input our precisely-determined pp cross sections at cosmic ray energies.  相似文献   

18.
We consider dark matter annihilation into standard model particles and show that the least detectable final states, namely, neutrinos, define an upper bound on the total cross section. Calculating the cosmic diffuse neutrino signal, and comparing it to the measured terrestrial atmospheric neutrino background, we derive a strong and general bound. This can be evaded if the annihilation products are dominantly new and truly invisible particles. Our bound is much stronger than the unitarity bound at the most interesting masses, shows that dark matter halos cannot be significantly modified by annihilations, and can be improved by a factor of 10-100 with existing neutrino experiments.  相似文献   

19.
The total charged-current (CC) (anti)neutrino-nucleon cross section is usually estimated by the sum of contributions from quasielastic scattering (QES), single-pion production through baryon resonances (RES), and deep-inelastic scattering (DIS) with an appropriate scratching of the phase space of the RES and DIS contributions. However, the resulting total cross section is very sensitive to the value of the cutoff in invariant mass of the final hadron system produced in RES and DIS. We examine available experimental data on the QES and total CC cross sections in order to extract the best-fit value for this cutoff. By using the same data set, we attempt to adjust the poorly known values of the axial mass for QES and RES. The text was submitted by the authors in English.  相似文献   

20.
The experimental data of ISR and NAL for the process pp → pX are used for the determination of the pomeron-particle total cross section and the triple-pomeron vertex. Estimates of the cross sections of the diffractive production of one and several showers of particles are given. It is shown that at s ~ 103 GeV2 the cross section of all inelastic diffractive processes is ~ 6 mb and grows with energy. A theoretical estimate of the amplitude of pomeron-pomeron scattering is given.  相似文献   

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