Measurement of elastic scattering in antiproton-proton collisions at 52.8 GeV centre-of-mass energy

We measured the differential cross section for p?p and pp elastic scattering in the momentum-transfer range 0.01 <|t| < 1.0 GeV² at the CERN Intersecting Storage Rings with center-of-mass energy $\text{s}\text{= 52.8}\text{GeV}$. Fitting the differential cross section with an exponential [Aexp (bt)], we found $\text{b}\text{p}\text{p = 13.92 ± 0.59}\text{GeV}{}^{\mathrm{?2}}$ for |t| < 0.05 GeV², whilst for |t| > 0.09 GeV², $\text{b}\text{p}\text{p = 10.68 ± 0.26}\text{GeV}{}^{\mathrm{?2}}$. Using the optical theorem, we obtained for the total cross section $\text{σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{p}\text{p)= 44.86 ± 0.78}\text{mb}$ and, by integrating the differential cross section, we obtained for the total elastic cross section $\text{σ}{}_{\mathrm{<mtext>el</mtext>}}\text{(}\text{p}\text{p) = 7.89 ± 0.28}\text{mb}$. Calculations of σ_tot combining elastic-rate and total-rate measurements are also given. All of these measurements were also performed for pp scattering at the same energy, and the results for both reactions are compared.     

Measurements of elastic scattering in alpha-alpha and alpha-proton collisions at the CERN intersecting storage rings

We measured the elastic scattering of $\text{αα}\text{at}\text{s}\text{= 126}\text{GeV}$ and of αp at $\text{s}\text{= 89}\text{GeV}$. For αα, the differential cross section dσ/dt has a diffractive pattern minima at |t| = 0.10 and 0.38 GeV². At small |t| = 0.05?0.07 GeV², this cross section behaves like exp[(100 ± 10) t]. Extrapolating a fit to the data to the optical point, we obtained for the total cross section α_tot(αα) = 250 ± 50 mb and an integrated elastic cross section σ_e1(αα) = 45 ± mb. Another method of estimating σ_tot(αα), based on measuring the interaction rate, yielded 295 ± 40 mb. For αp, dσ/dt has aminimum at |t| = 0.20 GeV², and for 0.05 < |t| < 0.18 GeV² behaves like exp[(41 ± 2) t]. Extrapolating this slope to |t| = 0, we found σ_tot(αp) = 130 ± 20 and σ_e1(αp) = 20 ± 4mb. Results on pp elastic scattering at $\text{s}\text{= 63}\text{GeV}$ agree with previous ISR experiments.     

On the difference between pp and pp topological cross sections up to 100 GeV/c

New 100 GeV/c$\text{p}$p data are used to find moments of the difference between the $\text{p}$p and pp topological cross sections. The mean multiplicity for annihilations at 100 GeV/c is estimated to be 9.06 ± 0.56, and the value of the quantity 〈n〉/D to be 2.75 ± 0.33. It is shown that $\text{R}{}_{\mathrm{n}}\text{= {σ}{}_{\mathrm{n}}\text{(}\text{p}\text{p) ? σ}{}_{\mathrm{n}}\text{(pp)}/σ}{}_{\mathrm{n}}\text{(pp)}$ appears at 100 GeV/c to have acquired an asymptotic form, R_n = s^?αβⁿ, with α and β constant.     

The size of inelastic diffraction dissociation

It is suggested that the inelastic diffraction dissociation cross section is a constant fraction β of the unitary bound, i.e. $\text{σ}{}_{\mathrm{DIFF}}\text{(s) = β[}\text{1}\text{2}\text{σ}{}_{\mathrm{TOT}}\text{(s) ? σ}{}_{\mathrm{EL}}\text{(s)]}$. Available data from pp collisions for s ? 20 (GeV/c)² are consistent with our hypothesis with $\text{β ～}\text{1}\text{2}$. Consideration of a specific model for diffraction suggests that the value of $\text{β ～}\text{1}\text{2}$ is a consequence of there being no lower mass state than pp with its quantum numbers. Predictions for πp and Kp scattering are presented.     

Peripheral pn production and decay angular distributions in the reaction π−p → (pn)p at 12 GeV/c incident momentum

The reaction $\text{π}{}^{\mathrm{?}}\text{p}\text{→ (}\text{p}\text{n}\text{)}\text{p}{}_{\mathrm{s}}$, where p_s is a slow proton, was measured at 12 GeV/c incident momentum with the CERN-OMEGA spectrometer. Both antiproton and proton were identified uniquely by electronics information. We obtained 1844 events with four-momentum Transfer squared in the range 0.13 ? |t| ? 0.33 GeV² and with invariant masses $\text{M(}\text{p}\text{n}\text{)}$ up to 2.5 GeV. The corresponding cross section in this t range is determined to be σ = 4 ± 0.4 μb. Extrapolating the differential cross section over the whole t range assuming dσ/dt ≈ exp(5.3t) we estimate a cross section of σ = 9.3 ± 2.0 μb. Comparison with data on $\text{π}{}^{\mathrm{?}}\text{p}\text{→ (}\text{p}\text{p}\text{)}\text{n}{}_{\mathrm{s}}$ (where n_s is a slow neutron) in the same t range shows that the $\text{(}\text{p}\text{n}\text{)}\text{p}{}_{\mathrm{s}}\text{and}\text{(}\text{p}\text{p}\text{)}\text{n}{}_{\mathrm{s}}$ cross sections have approximately the same magnitude.     

Multipomeron production of showers at high energy

Cross section of the multipomeron production of heavy showers is calculated and found at very high energy in the form $\text{σ′}{}_{\mathrm{<mtext>AB</mtext>}}\text{= [1 ? (}\text{s}{}_{\mathrm{<mtext>O</mtext>}}\text{s}\text{)}{}^{\mathrm{\gamma }}\text{] σ}{}_{\mathrm{<mtext>AB</mtext>}}{}^{\mathrm{<mtext>tot</mtext>}}$. It is shown that the multiperipheral part of the total cross section decreases at where the constant γ can be obtained from ISR data on proton spectra. It is found to be numerically very small γ ～ 10^?2. It follows that at accessible energies the value of $\text{σ′}{}_{\mathrm{<mtext>AB</mtext>}}\text{≈ (γ}\text{ln}\text{s}\text{s}{}_{\mathrm{<mtext>O</mtext>}}\text{)· σ}{}_{\mathrm{<mtext>AB</mtext>}}{}^{\mathrm{<mtext>tot</mtext>}}$ must be small, logarithmically increasing with energy. This prediction can be checked experimentally on new accelerators.     

Upper bounds on the fine structure constant and on nucleon magnetic moments in terms of Compton scattering cross sections

We derive and compare with experimental data the bound

$\text{α??λm}{}_{\mathrm{<mtext>p</mtext>}}\text{?m}{}_{\mathrm{<mtext>p</mtext>}}\text{ν}{}^2{}_1\text{2π}{}^2\text{∫}\text{ν}{}_0\text{∞}\text{d}\text{ν′σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(ν′)}\text{(ν′}{}^2\text{+ν}{}^2{}_1\text{)}\text{+2πm}{}_{\mathrm{<mtext>p</mtext>}}\text{∫}\text{ν}{}_0\text{∞}\text{ν′}{}^2\text{d}\text{ν′σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(ν′)}\text{(ν′}{}^2\text{+ν}{}^2{}_1\text{){ν′}{}^2\text{(}\text{d}\text{σ}\text{d}\text{t)}{}_0\text{+πλ}{}^2\text{+2ν′|λ|}\text{π}\text{(}\text{d}\text{σ}\text{d}\text{t)}{}_0\text{?}\text{σ}{}^2{}_{\mathrm{<mtext>tot</mtext>}}\text{16π}\text{}}{}^{\mathrm{?1}}$

, where α is the fine-structure constant, m_p the proton mass, ν₀ the photo-pion production threshold, σ_tot and $\text{(}\text{d}\text{σ}\text{d}\text{t}\text{)}{}_0$ are the unpolarized total hadronic photo-absorption cross section on protons and the unpolarized forward differential cross section for proton Compton scattering at photon-lab energy ν′, and λ and ν₁ are any real numbers. We derive similar bounds on proton and neutron magnetic moments.     

Multiplicity distributions and double-scattering effects in π−d interactions at 360 GeV/c

Double-scattering effects are studied in π^?d interactions at 360 GeV/c. The partial cross sections $\text{σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(π}{}^{\mathrm{?}}\text{d}\text{), σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(“π}{}^{\mathrm{?}}\text{p}\text{”)}\text{and}\text{σ}{}_{\mathrm{<mtext>N</mtext>}}\text{(“π}{}^{\mathrm{?}}\text{n}\text{”)}$ are presented. The double-scattering probability per πd collision is found to be $\text{? = 0.15 ± 0.02}$. We have extracted the partial cross section X_N of the double-scattering plus interference contributions, and find that X_N obeys KNO scaling. The data are compared with various theoretical predictions.     

Complete fusion studies of the 20Ne+235U system

The probability for complete fusion has been measured for the ²⁰Ne+²³⁵U system at bombarding energies of 175 and 252 MeV. The fission fragment angular correlation technique was used to obtain both the absolute cross section for complete fusion and relative cross sections for the ratio of complete fusion to incomplete fusion processes. Total reaction cross sections were also determined from elastic scattering measurements. Values of σ_R = 1900±40 and 2810 ± 140 mb were obtained at 175 and 252 MeV, respectively. These measurements yield if$\text{σ}{}_{\mathrm{<mtext>CF</mtext>}}\text{σ}{}_{\mathrm{<mtext>R</mtext>}}\text{= 0.74±0.05}\text{at}\text{175}\text{MeV and}\text{0.48 ±0.06}\text{at}\text{252}\text{MeV}$. The corresponding values of the critical angular momentum are compared with the predictions of several heavy-ion interaction models. It is observed that the l_c values obtained from these data agree well with the current models, although the energy dependence is not as strong as predicted. In addition, it is observed that these values of l_c exceed the limiting value for a charged rotating drop.     

Large p⊥ lepton production and the ψ(3100)

We determine the invariant cross section $\text{E}\text{d}\text{σ}\text{d}{}^3\text{p(s,x}{}_6\text{,pp}{}_{\mathrm{\perp }}\text{)}$ for pp→ψ(3100)+X near x₆=0 at NAL and ISR energies using the assumption that all large p_⊥ single leptons originate from the ψ. We adequately reproduce the single lepton data, and by suitable extrapolarion in x₆ ensure agreement with the NAL ψ production data (x₆?0.3). The magnitude of the resulting ψ production cross section is, however, roughly a factor of 3 larger than that observed by the recent CCRS-ISR experiment.     

Temperature variation of the magnetic cluster structures in an iron-nickel invar alloy

Small-angle scattering of long wavelength neutrons $\text{(λ = 6.42}\text{A}\text{?}\text{)}$ from an Fe₆₅Ni₃₅ single crystal has been measured with the applied magnetic field (6.2 kG) parallel and perpendicular to the scattering vector $\text{K}$ of the elastic scattering over the temperature range from 25 to 422°C (T_c = 227°C). The scattering cross sections due to the longitudinal spin fluctuation have been analyzed by means of Guinier's approximation $\text{(dσ/dω)}{}_0\text{exp}\text{(?κ}{}^2\text{R}{}_{\mathrm{<mtext>g</mtext>}}{}^2\text{3}\text{)}$, where the forward cross section (dσ/dω)₀ is proportional to n, which is the number of atoms in a paramagnetic cluster, and R_g is the radius of gyration of the cluster. The empirical relation between n and R_g is = 0.298 × R_g^2.34 to be compared with that calculated for a simple spherical cluster model n = 1.274 R_g³.     

Lorentz contracted geometrical model

The model assumes that when two high energy particles collide each behaves as a geometrical object which has a Gaussian density and is spherically symmetric except for the Lorentz-contraction in the incident direction. Folding the two spatial distribution together we obtain the slope (b) of the elastic diffraction peak in terms of the c.m. velocities (β_i and β_j) and the sizes (A_i and A_j) of the two incident particles. These sizes are assumed to have the experimental s-dependence of σ_tot ∝ πA² for each reaction. The combined s-dependence of the σ_tot's and the β's gives the s-dependence of the elastic slope $\text{b}{}_{\mathrm{ij}}\text{(s) =}\text{1}\text{2}\text{(A}{}_{\mathrm{i}}{}^2\text{β}{}_{\mathrm{i}}{}^2\text{+ A}{}_{\mathrm{j}}{}^2\text{β}{}_{\mathrm{j}}{}^2\text{)}\text{σ}{}^{\mathrm{ij}}{}_{\mathrm{<mtext>tot</mtext>}}\text{(s)}\text{σ}{}^{\mathrm{ij}}{}_{\mathrm{<mtext>tot</mtext>}}\text{(∞)}$. This formula agrees with the experimental slope for p-p, $\text{p}$-p, K⁺-p, K^?-p and π^±-p elastic scattering from 3 to 1500 GeV/c, with only 3 parameters: A_π² = 6.1, A_K² = 3.3 and A_p² = 10.5 (GeV/c)^?2.     

Experimental results on J/ψ production by π±, K±, p and p incident on hydrogen at 39.5 GeV/c

J/ψ production at 40 GeV/c by π^±, K^±, p and $\text{p}$ incident on hydrogen has been studied and results compared with those obtained on tungsten in the same experiment. On hydrogen, J/ψ cross-section ratios relative to π^? have been measured to be (for $\text{x}{}_{\mathrm{<mtext>F</mtext>}}\text{> 0) σ(π}{}^{\mathrm{?}}\text{) : σ(π}{}^{\mathrm{+}}\text{) : σ(}\text{p}\text{) : σ(}\text{p}\text{) = 1 : (0.78 ± 0.09) : (0.83 ± 0.35) : (0.07 ± 0.04)}$. The suppression of the proton induced cross sections shows the importance of calence quark-antiquark fusiin J/ψ production at this energy (i.e. M_J²/_ψ/s=0.13).     

Rising total cross sections and the flavoring of the pomeron

The relationship of the non-diffractive renormalization of the bare pomeron via$\text{K}\text{K}$ and $\text{B}\text{B}$ production - or its “flavoring” by λ quark loops and di-quark loops - and the shape of the NN total cross section is studied in some detail. The “unflavored” bare pomeron P? generated by non-strange quark loops with intercept $\text{α}\text{=0.85}$ is non-diffractively renormalized into the “flavored” (Gribov) bare pomeron P with intercept α above one (α = 1.06 here). We utilize inclusive data on $\text{K}\text{K}\text{and}\text{B}\text{B}$ production as well as inelastic diffraction to constrain parameters, and we fit the combination $\text{1}\text{2}\text{(σ}{}_{\mathrm{<mtext>pp</mtext>}}\text{+ σ}{}_{\mathrm{<mtext>p</mtext><mtext>p</mtext>}}\text{)}$ from s = 10 GeV² through ISR energies, including the new Fermilab data, to high accuracy. No pronounced long wavelength oscillations are observed. We suggest that these data favor the Chew-Rosenzweig realization of the topological expansion over that of Harari-Freund. We show that our scheme is consistent with the rising behavior of 2σ_KN ? σ_πN.     

Measurement of the νμ and νμ nucleon charged-current total cross sections,and the ratio of νμ neutron to νμ proton charged-current total cross sections

The total ν_μ and $\text{ν}{}_{\mathrm{\mu }}$ nucleon charged-current cross sections have been measured in BEBC filled with deuterium and exposed to the wide-band neutrino and antineutrino beams at the CERN-SPS. Assuming a linear energy dependence for the cross sections, σ = aE(?_ν, we obtained the coefficients , where the quoted error is mainly systematic. The ratio of the cross sections is $\text{σ}{}_{\mathrm{<mtext>\nu </mtext><mtext>N</mtext>}}\text{/σ}{}_{\mathrm{<mtext>\nu </mtext><mtext>N</mtext>}}\text{= 0.53 ± 0.03}$.We also determined the ratio of the charged-current cross section for neutrino interactions on neutrons and protons R = σ_νn/σ_νp = 2.10 ± 0.08 (statistical) ±0.22 (sysetmatic). The dependence of R on the variables x, y and E_ν is discussed.     

Electronic-excitation transfer collisions in flames-III: Cross sections for quenching and doublet mixing of Rb(52P32, 12) doublet by N2, O2, H2 and H2O

Weighted average quenching cross sections for the Rb(5²P) doublet by N₂ and H₂O were determined in flames with temperatures ranging from 1500 to 2500 K by measuring the fluorescence efficiency. The values found are $\text{(σ}{}_{\mathrm{qu}}\text{)}{}_{\mathrm{<mtext>N</mtext><mtext>2</mtext>}}\text{= (19±2)}\text{A}\text{?}{}^2$ and over the entire temperature range. At a temperature of 1720 K, mixing cross sections were obtained for the same doublet with N₂, H₂, O₂ and H₂O molecules. The cross sections found are: $\text{σ}{}_{21}\text{(}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{→}{}^2\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>N</mtext><mtext>2</mtext>}}\text{= (60±12)}\text{A}\text{?}{}^2$, $\text{σ}{}_{12}\text{(}{}^2\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{→}{}^2\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>N</mtext><mtext>2</mtext>}}\text{= 99±20)}\text{A}\text{?}{}^2$; , $\text{(σ}{}_{21}\text{)}{}_{\mathrm{<mtext>H</mtext><mtext>2</mtext>}}\text{> 30}\text{A}\text{?}{}_2$, $\text{(σ}{}_{12}\text{)}{}_{\mathrm{<mtext>H</mtext><mtext>2</mtext>}}\text{> 50}\text{A}\text{?}{}^2\text{;}$, . The ratios σ₁₂/σ₂₁ were measured independently and were found to agree with the detailed- balance condition within 3 per cent. A critical comparison of the flame values with previous literature data on N₂-cross sections shows that both mixing and quenching cross sections are temperature dependent in the range from 300 to 2500 K.     

Near 90° scattering in the channels K̄°p → π+Λ°, K̄°p → π+Σ° and KL°p → KS°p from 1.0 to 7.5 GeV/c

Differential cross sections for center of mass scattering angles near 90° are presented for the reactions $\text{K}\text{?}\text{°}\text{p}\text{→ π}{}^{\mathrm{+}}\text{Λ°}$, $\text{K}\text{?}\text{°}\text{p}\text{→ π}{}^{\mathrm{+}}\text{Σ°}$ and K_L°p → K_S°p in the momentum interval 1.0 to 7.5 GeV/c. The energy dependences of these cross sections are found to be equally well described by the parameterization: $\text{(}\text{d}\text{σ}\text{d}\text{Ω}\text{)}{}_{\mathrm{90°}}\text{∞ s}{}^{\mathrm{?2}}$ or $\text{(}\text{d}\text{σ}\text{d}\text{Ω}\text{)}{}_{\mathrm{90°}}\text{∞}\text{exp}\text{(? bp}{}_{\mathrm{\perp }}\text{)}$.     

Search for parity-nonconservation effects in deep-inelastic μ-N interaction

The difference of the cross sections for deep inelastic scattering of muons with average momenta 21 GeV/c with right and left helicity at large angles, i.e., with large momentum transfer, has been measured. No statistically-significant dependence of cross sections on the longitudinal polarization of muons has been found, i.e. no parity-nonconservation effects in deep inelastic μN interaction have been observed. The magnitude of the cross-section asymmetry $\text{R =}\text{[〈σ}{}_{\mathrm{<mtext>R</mtext>}}\text{〉 ? 〈σ}{}_{\mathrm{<mtext>L</mtext>}}\text{〉]}\text{[〈σ}{}_{\mathrm{<mtext>R</mtext>}}\text{〉+ + 〈σ}{}_{\mathrm{<mtext>L</mtext>}}\text{〉]}$ may be represented as R = β〈Q²〉 = (? 4 ± 6) × 10^?3 〈Q², (GeV/c)²〉. The limitations G_o^(μ) = (+ 6 ± 10)G have been obtained for the constant G_o^(μ) of vector-axial interaction $\text{(}\text{G}{}_{\mathrm{<mtext>o</mtext>}}{}^{\mathrm{(\mu )}}\text{2}\text{) [}\text{μ}\text{γα(1 + γ}{}_5\text{)μ] J}{}_{\mathrm{\alpha }}{}^{\mathrm{<mtext>o</mtext>}}$ (hadron, V-A).     

Baryon-antibaryon annihilations,unitarity and the pomeron

We show that baryon-antibaryon annihilations into mesons contribute, via unitarity, mainly to the pomeron term in the total $\text{B}$B cross section. The meson-exchange term is mainly built by non-annihilation processes. These results are contrary to previous ideas according to which $\text{B}$B annihilations are responsible for the difference between $\text{σ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(}\text{B}\text{B}\text{)}$ and σ_tot(BB) and contribute to the meson exchange term. Our conclusions are based on an explicit duality diagram model which we discuss in some detail. However, a much wider class of models give similar results. Experimental tests of our ideas are proposed.     

Activation cross section for 27Al(π+,π0)27Si at 100 MeV

The activation cross section for ${}^{27}\text{Al}\text{(π}{}^{\mathrm{+}}\text{,π}{}^0\text{)}{}^{27}\text{Si at}\text{E}{}_{\mathrm{\pi }}\text{= 99 ± 9}\text{MeV}$ was determined to be 5.1 ± 2.2 mb by counting the residual β⁺ activity of ²⁷Si. This result is compared with other pion-nucleus cross sections. A value for the elementary pion-nucleon cross section inside the nucleus is derived from this result and compared with an estimate from a phenomenological expression.