A t-channel isospin analysis of the chew-low plot for NN → N(Nπ) interactions at 5.7 GeV/c

A new approach to the t-channel isospin analysis of ZN → Z′(Nπ) reactions is presented. This approach, useful for $\text{Z = N,}\text{N}\text{, K}{}^{\mathrm{?}}$ when only five independent sets of data are availables, is used to analyse data of $\text{N}\text{N →}\text{N}\text{(Nπ)}$ reactions obtained in a $\text{p}\text{p →}\text{N}\text{N}\text{π}$ experiment at $\text{5.7}\text{GeV}\text{/c}\text{and a}\text{p}\text{d →}\text{N}\text{Nπp}{}_{\mathrm{s}}$ experiment at 5.5 GeV/c. the t behaviour of the different isospin exchange amplitudes, suggests their exchange mechanism production. The mass spectrum, M_πN, of the contributions produced by exchanged isospin I_ex = 1, shows enhancements corresponding to N(1490) N(1670) and Δ(1230) isobars, while the mass spectrum for I_ex = 0 presents only a large bump at ～1350 MeV commonly identified as N¹(1400).     

Isospin analysis of NN → NNπ reactions at 5.7 GeV/c

A cross-channel isospin analysis has been performed on the channels $\text{p}\text{N}\text{→}\text{N}\text{(}\text{N}\text{π)}\text{and}\text{p}\text{N}\text{→}\text{N}\text{(}\text{N}\text{π)}$ in terms of three isospin amplitudes $\text{M}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^0\text{, M}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^1$, and $\text{M}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^1$ where the upper index is the isospin of the exchanged “object” in the t-channel and the lower index is the isospin of the $\text{(}\text{N}\text{π)}\text{or}\text{(}\text{N}\text{π)}$ system. Enhancements are observed in the low Nπ) invariant mass region for an $\text{I =}\text{1}\text{2}$ final state when the isospin of the exchanged object in cross channel is I_E = 0 and 1.     

Possible heavy lepton signals at pp colliders

If a new sequential heavy lepton L exists with mass below that of the W boson, it will give rise to the following decay chains: W → Lν_Lwith $\text{L}\text{→}\text{e}\text{ν}{}_{\mathrm{<mtext>e</mtext>}}\text{ν}{}_{\mathrm{<mtext>L</mtext>}}$ or $\text{L}\text{→}\text{Q}\text{qν}{}_{\mathrm{<mtext>L</mtext>}}$. We critically study, and quantify, the possibility of identifying this heavy lepton signal against the various backgrounds in high energy p?p collision. We find that the leptonic decay signal is plagued by serious b?b, W → eν, and W → τν backgrounds, whereas the hadronic decay mode leads to a distinctive signature, after selected cuts are applied. We discuss how the mass of such a lepton may be determined.     

Superconducting properties of ZnCr and ZnMn alloys

Measurements on the superconducting critical temperature T_c and critical field, H_c, of $\text{Zn}$Cr and $\text{Zn}$Mn alloys, down to 0.037°K are presented.The variation of T_c with increasing concentration depends strongly on T_cp/θ, with θ a characteristic temperature, while effects of H_c are similar to previously studied alloys.     

Nonrelativistic distorted wave born approximation predictions for 500 MeV (p, p') spin-rotation observables

We discuss couplings of scalar gluonium σ on the basis of the low energy theorems of broken chiral symmetry and the anomalous trace of the energy—momentum tensor, implemented using a phenomenological lagrangian. Taking the ITEP value of the gluon consensate as input, we find $\text{Γ(σ → ππ) ? 0.6}\text{GeV}\text{× (}\text{m}{}_{\mathrm{\sigma }}\text{1}\text{GeV}\text{)}{}^5$ and $\text{Γ(σ → γγ) ? 90}\text{eV}\text{× (}\text{m}{}_{\mathrm{\sigma }}\text{1}\text{GeV}\text{)}{}^5$, while m_σ is undetermined. These results suggest that if the scalar gluonium mass is above 1 GeV, it is probably unobservably wide, while production in γγ collisions is probably too small to be detectable if m_σ < 1.5 GeV. We comment on the observability of J/ψ → σ + γ and on the relevance of our results to other gluonia.     

Coupled channel study on the S-wave ππ → KK interaction

We perform a dispersion relation type calculation of the I = 0 S-wave amplitude g₀⁺ (t) for the process $\text{ππ →}\text{K}\text{K}$, in the region from t = 4μ² to t = (1100 MeV)². Crossing is imposed by generalizing the newly developed hyperbolic partial-wave relations to our reaction and by imposing them on our amplitude using experimental Kπ phase-shift information as input. Analyticity and unitarity is imposed by generalizing the formalism of BFP [1] for parametrizing partial-wave amplitudes. This readily allows us to impose the experimental $\text{ππ →}\text{K}\text{K}$ cross section. Finally the low energy behaviour is constrained to lie within certain limits recently deduced from fixed-tKπ dispersion relation studies [2] and including the current algebra prediction as a special case. We are able to resolve a previous controversy regarding the sign of Im g₀⁽⁺⁾ (t).     

Pseudoscalar mesons in the c-c and b-b systems

It is shown that the pseudoscalar η_c and “η_c” (η_b and “η_b”) with M ≈ 2.80 and 3.51 GeV (9.17 and 9.88 GeV) can be predicted by using the radial mixing model, where the “η_c” and “η_b” are the excited 0^- states in the $\text{c-}\text{c}$ and $\text{b-}\text{b}$ systems, respectively, and the former would correspond to the observed 0^- meson with M ≈ 3.45 GeV in charmonium.     

Vector meson pole dominance in Jψ decays into mesons

The validity of the assumption that $\text{J}\text{ψ}$ decays into mesons proceed via ω, φ and ?⁰ poles followed by cascade decays is examined. $\text{Λ(}\text{J}\text{ψ}\text{→}\text{B}\text{π)}$ is well reproduced by using $\text{Λ(}\text{J}\text{ψ}\text{→ ?π), Λ(ω → ?π), Λ(}\text{B}\text{→ ωπ)}$ and the B → ωπ helicity structure. The structure of OZI-violating $\text{J}\text{ψ}\text{?}\text{V}{}^0$ transitions including the electromagnetic contribution is examined, and compared with the data on inclusive $\text{J}\text{ψ}$ decay.     

Evidence for high mass NN and NNπ enhancements observed in pd interactions at 5.55 GeV/c

Based on 4085 $\text{p}\text{n→Xπ}{}^{\mathrm{?}}$ events, X denoting a neutral $\text{N}$N or $\text{N}\text{Nπ}$ system, we present evidence for 5.1 and 3.1 standard deviation enhancements at the X mass of 2.85 and 3.05 GeV/c², respectively. The lower mass bump has a width of Λ ? 39 GeV/c² while the 3.05 GeV/c² is seen as a one bin accumulation (20 GeV/c² width). The relevance of these peaks is discussed.     

Magnetostriction of dilute AuYb and AuTb monocrystals

We have made magnetostriction measurements on dilute $\text{Au}$Yb and $\text{Au}$Tb monocrystals at low temperatures. The shape magnetostriction follows the sign of the quadrupolar Stevens factor α_J of the earth but, in contrast to our recent results on silver-rare earth dilute alloys, the 〈001〉 and 〈111〉 effects have opposite signs. We obtain very good agreement between experiment and calculations based on the known cubic crystal-field parameters and we estimate the ion-lattice coupling parameters. The volume magnetostriction is positive, but very small, about two orders of magnitude smaller than the shape effect.     

A study of ππ → NN partial-wave amplitudes using hyperbolic dispersion relations

We investigate $\text{ππ →}\text{N}\text{N}$ partial-wave amplitudes, using a spin separation method based on hyperbolic dispersion relations. Partial-wave amplitudes with J ? 3 are dominant in the pseudophysical region between the ππ and $\text{N}\text{N}$ thresholds, but we find clear evidence for J = 4 and J = 5 contributions from regions near and above the $\text{N}\text{N}$ threshold. We isolate J = 2 and J = 3 partial waves and determine the couplings of f₀(1270) and g (1680). Knowing the high-spin contributions, we are able to eliminate thse and to study s- and p-waves. We find evidence for small p-wave contributions above the ?, having the same sign as the ? contributions. We develop methods for determining the I = J = 0 ππ scattering length a₀⁰ and find a₀⁰ = 0.30 ± 0.15.     

Angular distributions and structure functions from two-jet events at the CERN SPS pp collider

The two-jet cross section measured in the UA1 apparatus at the CERN $\text{p}\text{p}$ Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x₁ and x₂. The angular distribution dσ/d cos σ rises rapidly as cos → 1, independent of x₂ and x₂, as expected in vector gluon theories (QCD). The differential cross section in x₁ and x₂ is consistent with factorization and provides a measurement of the proton structure function $\text{F(x) = G(x) +}\text{4}\text{9}\text{[Q(x) +}\text{Q}\text{(x)]}$ at values of the four-momentum transfer squared, -t? ≈ 2000 GeV². Over the range x = 0.10?0.80 the structure function shows an exponential x dependence and may be parametrized by the form F(x) = 6.2 exp (?9.5x).     

Jets in pp collisions: Radiation zeroes and the electric charges of colored quarks

Measurements involving more than one photon (e.g., γγ → hadrons, e⁺e^- → q$\text{q}$γ) can determine the electric charge of colored quarks rather than the color-averaged value measured, for example, by the R-value in e⁺e^- → hadrons. We draw attention to the fact that this measurement of the absolute quark charges can be performed in hadron collisions via the process qq → qqγ. The charge signature is dramatic due to the appearance of radiation zeroes whose position depends on the values of the electric charges. This can be exploited to perform such measurements with a detector lacking γ/π⁰ separation capability. Such experiments also study the interface of color and electromagnetic amplitudes and can further elucidate the QCD origin of jets.     

Features of diffractive scattering and the nature of the N1(1400) observed in NN→N(Nπ) reactions at 5.7 GeV/c

The results for the diffractive scattering contribution ($\text{F}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^0$) obtained in a cross channel isospin analysis of the $\text{N}\text{N}\text{→}\text{N}\text{(}\text{N}\text{π)}$ reactions at 5.7 GeV/c are compared with those obtained for other ZN → Z′(Nπ) reactions where Z stands for N, π and the carbon nucleus. The dependence of the diffractive scattering on the mass M_πN and the momentum transfer t seems very weakly related to the nature of Z and the incident momentum.A comparison between amplitudes of the isospin exchange I_ex = 0 and I_ex = 1 leading to $\text{N}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ production shows that $\text{N}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(1492)}$ and $\text{N}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(1670)}$ are produced essentialy through I_ex = 1.     

D-state effects in (d, t) and (d, 3He) reactions

The influence of the deuteron and triton [³He] D-state on the form factor required in the DWBA analyses of the ($\text{d}$, t) [($\text{d}$, ³He)] reactions has been studied. The wave functions of Phillips are used for three-nucleon systems because they are designed to yield the correct asymptotic form for the (d, t) and (d, ³He) overlaps. The zero-range parameters D₀ and D₂ which enter into the calculation of the cross section and the tensor analysing power in the DWBA with the local energy approximation are calculated and found to yield values consistent with experimental data.     

HD structural isotope effect in hydrogen-bonded 2-aminoethanol

The microwave spectra of the d₃ species of intramolecularly hydrogen-bonded 2-aminoethanol (ODCH₂CH₂ND₂) as well as the d₃-O¹⁸, d₃-N¹⁵ and three d₂ isotopic forms have been studied. The r_s O-(D)?N distance of 2.8027(5) Å in the d₃ species is 0.0058(7) Å shorter than the O-(H)?N distance found earlier for the d₀ species (R. E. Penn and R. F. Curl, Jr., J. Chem. Phys.55, 651–658 (1971)). The anomalous r_s structural parameters $\text{r}\text{OH = 1.14}\text{A}\text{?}$ and ∠COH = 103.7°, when corrected for the systematic error caused by the O?N “shrinkage” upon deuteration, become 1.00 Å and 108°, respectively.     

The impurity resistivity and resistivity minima in AlCr and AlMn alloys

The impurity resistivity of $\text{Al}$Cr between 1.5 and 50°K was determined with a characteristic temperature for the T² variation θ₁=960±40°K. The behaviour of the resistivity minimum both in $\text{Al}$Cr and $\text{Al}$Mn alloys with impurity concentration provides evidence that a T³ phonon resistivity is found also in aluminium with anomalous impurity resistivity.     

Observation of a KK enhancement at 1.85 GeV in the reaction K−p → KKΛ at 8.25 GeV/c

In a high statistics $\text{(}\text{～150 eV}\text{μb}\text{)}$ bubble chamber experiment on K^?p interactions at 8.25 $\text{GeV}\text{c}$, the study of the reaction K^?p → KKΛ provides evidence for an enhancement in the KK system with a mass of (1850 ± 10) MeV and a width of (80_?30⁺⁴⁰) MeV. Its possible identification with the missing isosinglet of the 3^? nonet is discussed. A K¹$\text{K}$ decay mode is also observed.     

Differential cross section zeros for the process NN → ππ

We describe a method for examining the differential cross section zeros for the process spin $\text{(}\text{1}\text{2}\text{+}\text{1}\text{2}\text{) →}\text{spin}\text{(0 + 0)}$. This is illustrated using the reaction $\text{p}\text{p}\text{→ π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$, where three dominant meson spin states are shown to exist in the mass range 2020 to 2580 MeV/c².     

A phenomenological investigation of ππ → KK partial-wave amplitudes from hyperbolic dispersion relations

We calculate the $\text{ππ →}\text{K}\text{K}$ partial-wave amplitude g_J^(+-), J = 0, 1, 2, 3, in the unphysical region below the $\text{K}\text{K}$ threshold using partial-wave relations derived from hyperbolic dispersion relations. For g₁^(?) the results are in agreement with earlier calculations and we confirm the current low-energy predictions. For g_o⁽⁺⁾ we favour a down-type solution with a large positive $\text{K}\text{K}\text{→}\text{K}\text{K}$ s-wave scattering length.