Search

The semi-leptonic decay of the neutral K meson $K^{0}_{L} \to \pi^{\pm}e^{\mp}\nu (K_{e3})$, was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector $(f_{+}(q^{2}))$, scalar $(f_{S})$ and tensor $(f_{T})$ interactions were measured. The linear slope of the vector form factor $\lambda_{+} = 0.0284 \pm 0.0007 \pm 0.0013$ and values for the ratios $|f_{S}/f_{+}(0)|=0.015^{+0.007}_{-0.010} \pm 0.012$ and $|f_{T}/f_{+}(0)|=0.05^{+0.03}_{-0.04} \pm 0.03$ were obtained. The values for $f_{S}$ and for $f_{T}$ are consistent with zero. Assuming only vector-axial vector couplings, $\lambda_{+} = 0.02888 \pm 0.0004 \pm 0.0011$ and a good fit consistent with pure V-A couplings were obtained. Alternatively a fit to a dipole form factor yields a pole mass of $M = 859 \pm 18$ MeV, consistent with the $K^{*}(892)$ mass. The semileptonic decay of the neutral K meson, KL0→π±e∓ν ( Ke3 ), was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector (f+(q2)) , scalar ( fS ) and tensor ( fT ) interactions were measured. The linear slope of the vector form factor λ+=0.0284±0.0007±0.0013 and values for the ratios |fS/f+(0)|=0.015−0.010+0.007±0.012 and |fT/f+(0)|=0.05−0.04+0.03±0.03 were obtained. The values for fS and fT are consistent with zero. Assuming only vector–axial-vector couplings, λ+=0.0288±0.0004±0.0011 and a good fit consistent with pure V–A couplings were obtained. Alternatively, a fit to a dipole form factor yields a pole mass of M=859±18 MeV , consistent with the K*(892) mass. The semileptonic decay of the neutral K meson, KL -> pi e nu (Ke3), was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector (f_+(q^2)), scalar (f_S) and tensor (f_T) interactions were measured. The linear slope of the vector form factor lambda_+ = 0.0284+-0.0007+-0.0013 and values for the ratios |f_S/f_+(0)| = 0.015^{+0.007}_{-0.010}+-0.012 and |f_T/f_+(0)| = 0.05^{+0.03}_{-0.04}+-0.03 were obtained. The values for f_S and f_T are consistent with zero. Assuming only Vector-Axial vector couplings, lambda_+ = 0.0288+-0.0004+-0.0011 and a good fit consistent with pure V-A couplings were obtained. Alternatively, a fit to a dipole form factor yields a pole mass of M = 859+-18 MeV, consistent with the K^*(892) mass.

With the E731 apparatus at Fermilab, we have simultaneously collected 6859 ${\mathit{K}}_{\mathit{L}}$ and ${\mathit{K}}_{\mathit{S}}$ decays into ${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\gamma}. Using our sample of over 370 000 ${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ decays for normalization we have determined that the ratio \ensuremath{\Gamma}(${\mathit{K}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\gamma})/\ensuremath{\Gamma}(${\mathit{K}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$) is (23.0\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ for ${\mathit{K}}_{\mathit{L}}$ and (7.10\ifmmode\pm\else\textpm\fi{}0.22)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ for ${\mathit{K}}_{\mathit{S}}$, for photon energies greater than 20 MeV in the kaon center of mass. After removing the inner-bremsstrahlung contribution, we find that the photon energy spectrum of the direct emission decay of the ${\mathit{K}}_{\mathit{L}}$ is consistent with the presence of a vector meson propagator in the form factor.

Interference between ${\mathrm{K}}_{\mathrm{S}}$ and ${\mathrm{K}}_{\mathrm{L}}$ decays into the final state ${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\gamma} has been observed in experiment 731 at Fermilab. By fitting the distribution of decays downstream of a regenerator, a new CP-violation parameter${\mathrm{\ensuremath{\eta}}}_{+\mathrm{\ensuremath{-}}\ensuremath{\gamma}}$, analogous to ${\mathrm{\ensuremath{\eta}}}_{+\mathrm{\ensuremath{-}}}$, has been measured, with its magnitude equal to(2.15\ifmmode\pm\else\textpm\fi{}0.26\ifmmode\pm\else\textpm\fi{}0.20)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$, and ${\mathrm{\ensuremath{\varphi}}}_{+\mathrm{\ensuremath{-}}\ensuremath{\gamma}}$, the associated phase angle, equal to(72\ifmmode\pm\else\textpm\fi{}23\ifmmode\pm\else\textpm\fi{}17)\ifmmode^\circ\else\textdegree\fi{}. Assuming that any difference between this fit value for ${\mathrm{\ensuremath{\eta}}}_{+\mathrm{\ensuremath{-}}\ensuremath{\gamma}}$ and the previously measured value for${\mathrm{\ensuremath{\eta}}}_{+\mathrm{\ensuremath{-}}}$ can be attributed to direct CP violation in this decay, a limit of|${\mathrm{\ensuremath{\epsilon}}}_{+\mathrm{\ensuremath{-}}\ensuremath{\gamma}}^{\ensuremath{'}}$|/\ensuremath{\epsilon}0.3 at the 90% confidence level has been made. \textcopyright{} 1993 The American Physical Society

A study of prompt neutrino events from 400 GeV protons on a beam-dump is presented. The ratio of electron- to muon-neutrino rates is 0.86±0.14, in agreement withe−μ universality. The anti-neutrino to neutrino flux ratio is $$\bar v_\mu /v_\mu = 0.81 \pm 0.19$$ . The absolute rates and distributions observed are shown to be in quantitative agreement with the known properties of charmedquark production in hadron collisions.

Using the complete Fermilab E371 data set, we find {Gamma}({ital K}{sub {ital L}}{r arrow}{pi}{sup 0}{gamma}{gamma},+{ital m}{sub {gamma}{gamma}}{ge}0.280 GeV)/{Gamma}({ital K}{sub {ital L}}{r arrow}all) =(1.86{plus minus}0.60{plus minus}0.60){times}10{sup {minus}6}, in good agreement with a recent report of the first observation of this decay. For the low {gamma}{gamma} mass region we find {Gamma}({ital K}{sub {ital L}}{r arrow}{pi}{sup 0}{gamma}{gamma},{ital m}{sub {gamma}{gamma}}{lt}0.264 GeV)/{Gamma}({ital K}{sub {ital L}}{r arrow}all){lt} 5.1{times}10{sup {minus}6} (90% confidence).

Data collected by the E731 experiment at Fermilab were used to search for {ital CPT} violation in {ital K}{sup 0}{r arrow}{pi}{pi} decays by measuring the difference {Delta}{phi} between the phases of the {ital CP}-violating parameters {eta}{sub 00} and {eta}{sub +{minus}}. Our result, {Delta}{phi}={minus}0.3{degree}{plus minus}2.4{degree}{plus minus}1.2{degree}, where the first error is statistical and the second systematic, is consistent with {ital CPT} symmetry.

A new beam line and detector were constructed to increase statistical precision and greatly reduce systematic uncertainty on the ratio of the CP-nonconserving parameters epsilon'/epsilon. Major improve- ments are discussed together with a result from a first run: epsilon'/epsilon = 0.0032 +- 0.0028 (statistical) +- 0.0012 (systematic). The precision is better than earlier measurements yet the result is still consistent with the superweak mechanism (which predicts zero) and that due to Kobayashi and Maskawa. Significantly more data are being collected.

The authors report on the analysis of inclusive neutral current events produced in neutrino and antineutrino narrow band beams. One finds for incident neutrino energies in the range 12-200 GeV and for hadron energies above 12 GeV a neutral charged current cross-section ratio of R/sub nu /=0.293+or-0.010 for incident neutrinos, and R/sub anti nu /=0.35+or-0.03 for antineutrinos. These ratios are consistent with the Weinberg-Salam model, with sin/sup 2/ theta /sub w/=0.24+or-0.02. (6 refs).

Results of an experiment to measure the cross section for production of the D*/sup +/(D*/sup -/) in 200-GeV/c r/sup -/N interactions are reported. 78 +- 26 events are observed, corresponding to a D* production cross section ds/dy = 1.6 +- 0.5 mb at y = 0.

Primakoff production of the K/sup 0asterisk/(896) by incident K/sub L/'s was observed in the energy range 100--200 GeV. Production from Cu and Pb targets was measured simultaneously leading to a new value for the K/sup 0asterisk/(896) radiative width GAMMA(K/sup 0asterisk/(896)..-->..K/sup 0/+..gamma..) of 116.5 +- 9.9 keV. The result agrees with a previous determination while being considerably more precise and allows for more stringent tests of quark-model relations among the radiative widths of the low-lying vector mesons.

The properties of 76 neutrino-initiated μ − μ − μ + events observed in the CDHS detector in the 350 GeV and 400 GeV wide-band beams at CERN are discussed. For neutrino energies 30 GeV and muon momenta ≳4.5 GeV, the average trimuon rate is (3.0 ± 0.4) × 10 −5 of the single-muon event rate. The experimental distributions are compared with predictions from various models. The data cannot be understood in terms of either heavy-lepton or heavy-quark cascades; no evidence is found for such processes and upper limits for the two possibilities are established. The data can be understood in terms of the normal charged-current process with the additional production of a muon pair by both hadronic and electromagnetic processes.

Data taken in a Fermilab experiment designed to measure to CP-violation parameter epsilon/epsilonfrom a study of K..-->..2..pi.. decays were used to look for the as yet unseen decay modes K/sub L//sub ,//sub S/..--> pi../sup 0/e/sup +/e/sup -/. The detector was optimized for the detection of kaon decays with four electromagnetic showers in the final state. The results (90% confidence) are branching ratios pi../sup 0/e/sup +/e/sup -/ and K/sub S/..--> pi../sup 0/e/sup +/e/sup -/, respectively.

The scaling violations of the structure functionsF 2,xF 3, and $$\bar q$$ , as measured in deep-inelastic neutrino-nucleon scattering at high hadron massW, have been compared with the predictions of QCD and other candidate field theories of strong interactions. Non-asymptotically free theories with scalar and vector gluons are incompatible with the data. This leaves QCD as the only field theory that gives a consistent description of all the observed scaling violations. The data do not, however, permit a sensitive test of the existence of the gluon self-coupling.

We describe the design, construction and performance of a large mass detector used at CERN to study high-energy neutrino interactions in iron. This detector combines magnetic spectrometry and hadron calorimetry techniques.

An upper limit GAMMA(K/sup 0//sup */(1430)..-->..K/sup 0/..gamma..)

The ratio R-italic/sub ..nu../ of the neutral- to charged-current cross sections of neutrinos in iron has been measured in an exposure of the CERN-Dortmund-Heidelberg-Saclay neutrino detector to a 160-GeV/c-italic neutrino narrow-band beam at the CERN Super Proton Synchrotron. The result is R-italic/sub ..nu../ = 0.3072 +- 0.0025(stat) +- 0.0020(syst), for hadronic energy greater than 10 GeV. The electroweak mixing parameter is sin/sup 2/theta/sub W/ = 0.225 +- 0.005(expt ) +- 0.003(theor)+0.013(m-italic/sub c-italic/-1. 5 GeV/c-italic/sup 2/), where m-italic/sub c-italic/ is the charm-quark mass.

The energy resolution and response of a segmented iron-scintillator total absorption calorimeter has been measured for pion energies from 10 to 140 GeV and for electron energies up to 50 GeV. A procedure has been found to weight individual counter responses for hadron showers which results in improved energy resolution at high energies and a nearly linear dependence of response on hadron energy above 30 GeV. There is evidence in the data that this weighting procedure compensates for fluctuations in energy deposition due to the electromagnetic component of the hadronic shower. For an iron sampling thickness of 2.5 cm the hadron energy resolution follows a 0.58 E law, while the resolution for electromagnetic showers is 0.23 E .

A measurement of the ratio of the CP-nonconservation parameters, epsilon'/epsilon, in the K/sup 0/K /sup 0/ system was performed through a study of two-pion decays with and without a regenerator. To reduce systematic effects, K/sub L/ and K/sub S/ decays were recorded simultaneously with a double beam. Over 3100 K/sub L/..-->..2..pi../sup 0/ events were reconstructed leading to the result epsilon'/epsilon = -0.0046 +- 0.0053 +- 0.0024 (the first error is statistical, the second systematic). The measurement agrees with previous less precise determinations but, because of theoretical uncertainties, is not able to test decisively the Kobayashi-Maskawa mechanism.

The properties of 76 neutrino‐initiated μ−μ−μ+ events observed in the CDHS detector in the 350 GeV and 400 GeV wide‐band beams at the CERN SPS are discussed. For neutrino energies ≳30 GeV and muon momenta ≳4.5 GeV, the average trimuon rate is (3.0±0.4) ×10−5 of the single‐muon event rate. The data are in agreement with normal charged‐current interactions with the additional production of a muon pair by both hadronic and radiative processes. No evidence is found for either heavy‐lepton or heavy‐quark cascades. Upper limits for these two possibilities are established.

An experiment on the decay K/sup +/ ..-->.. ..pi../sup +/..pi../sup -/e/sup +/..nu.. was performed at the CERN proton synchrotron with spark-chamber and counter techniques. The K/sub e//sub 4/ branching ratio has been measured relative to the tau decay. The ..pi pi.. phase-shift difference delta/sup 0//sub 0/ - delta/sup 1//sub 1/ and the form factors of the hadronic current have been determined as functions of the ..pi pi.. energy. The ..pi pi.. scattering length a/sup 0//sub 0/ has been evaluated from the phase shifts with a phenomenological model. The results are compared with the theoretical predictions of current-algebra and other models.

In the interactions of 400 GeV/c protons with copper nuclei, a flux of prompt neutrinos is observed. The reactions produced by these neutrinos in our apparatus appear consistent with those of electron- and muon-neutrinos. The prompt neutrino fluxes are interpreted as being due to associated production and subsequent semileptonic decay of charmed hadrons. The prompt flux ratio $$\bar v_\mu /v_\mu = 0.46_{ - 0.16}^{ + 0.21} $$ suggests a sizeable production of charmed baryons near the forward direction. The ratio of prompte −+e + toµ −+µ + event rates is 0.64 −0.15 +0.22 , where unity is expected frome-μ universality.

We have calibrated a magnetized iron-scintillator sandwhich calorimeter in a hadron beam, finding an energy resolution equal to 16% fwhm at 140 GeV with 5 cm sampling. The hadron energy resolution (fwhm/mean) improves as E − 1 2 between 15 and 140 GeV. No effect due to the magnetic field was observed. Longitudinal and lateral shower containment were also investigated.

Results are presented of a measurement of the production of ${D}^{\mathrm{*}+}$ (${D}^{\mathrm{*}\mathrm{\ensuremath{-}}}$) in 250-GeV/c ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$N interactions. We observe 2.1\ifmmode\pm\else\textpm\fi{}7.8 events corresponding to a charge-${D}^{\mathrm{*}}$ cross section \ensuremath{\sigma}(${D}^{\mathrm{*}}$) of 0.4\ifmmode\pm\else\textpm\fi{}1.5 \ensuremath{\mu}b/nucleon. When averaged with our previous measurement made at 200 GeV/c, the result is \ensuremath{\sigma}(${D}^{\mathrm{*}}$)=2.3\ifmmode\pm\else\textpm\fi{}1.0 \ensuremath{\mu}b/nucleon with (d\ensuremath{\sigma}/dx)${\ensuremath{\Vert}}_{x=0}$=4.6\ifmmode\pm\else\textpm\fi{}2.0 \ensuremath{\mu}b.

We have measured the ratio GAMMA(K/sub L/..--> pi../sup +/..pi../sup -/)/GAMMA(K/sub L/..--> pi..l..nu.. ) to be (3.13 +- 0.14) x 10/sup -3/ for K/sub L/ with a mean laboratory momentum of 65 GeV/c. This value corresponds to the CP-nonconservation parameter Vertical Bareta/sub +/-Vertical Bar = (2.28 +- 0.06) x 10/sup -/ 3, and is consistent with the world average Vertical Bareta/sub +/-Vertical Bar = (2.274 +- 0.022) x 10 /sup -3/ which is derived from measurements with K/sub L/ laboratory momenta less than 10 GeV/c. In this experiment we find no evidence for an energy dependence of Vertical Bareta/sub +/-Vertical Bar.