201 research outputs found
Pseudorapidity Distribution of Charged Particles in PbarP Collisions at root(s)= 630GeV
Using a silicon vertex detector, we measure the charged particle
pseudorapidity distribution over the range 1.5 to 5.5 using data collected from
PbarP collisions at root s = 630 GeV. With a data sample of 3 million events,
we deduce a result with an overall normalization uncertainty of 5%, and typical
bin to bin errors of a few percent. We compare our result to the measurement of
UA5, and the distribution generated by the Lund Monte Carlo with default
settings. This is only the second measurement at this level of precision, and
only the second measurement for pseudorapidity greater than 3.Comment: 9 pages, 5 figures, LaTeX format. For ps file see
http://hep1.physics.wayne.edu/harr/harr.html Submitted to Physics Letters
A precision measurement of direct CP violation in the decay of neutral kaons into two pions
The direct CP violation parameter Re(epsilon'/epsilon) has been measured from
the decay rates of neutral kaons into two pions using the NA48 detector at the
CERN SPS. The 2001 running period was devoted to collecting additional data
under varied conditions compared to earlier years (1997-99). The new data yield
the result: Re(epsilon'/epsilon) = (13.7 +/- 3.1) times 10^{-4}. Combining this
result with that published from the 1997, 98 and 99 data, an overall value of
Re(epsilon'/epsilon) = (14.7 +/- 2.2) times 10^{-4} is obtained from the NA48
experiment.Comment: 19 pages, 5 figures, to be published in Physics Letters
Space charge in ionization detectors and the NA48 electromagnetic calorimeter
The subject of space charge due to positive ions slowly moving in parallel plate ionization chambers is considered. A model for the degradation of the detector response is developed, with particular emphasis on electromagnetic calorimeters. The topics discussed include: (a) the stationary and (b) the time dependent cases; (c) the limit of very large space charge; (d) the electric field dependence of the electron drift velocity; (e) the effect of longitudinal development of showers; (f) the behavior of the average reductions of response and (g) the non-uniformity of response for different positions of the shower axis inside the cell defined by the electrodes. The NA48 calorimeter is used as application and for comparison of results
A new measurement of direct CP violation in two pion decays of the neutral kaon
The NA48 experiment at CERN has performed a new measurement of direct CP
violation, based on data taken in 1997 by simultaneously collecting K_L and K_S
decays into pi0pi0 and pi+pi-. The result for the CP violating parameter
Re(epsilon'/epsilon) is (18.5 +/- 4.5(stat)} +/- 5.8 (syst))x10^{-4}.Comment: 18 pages, 6 figure
Measurement of the branching ratios of the decays Xi0 --> Sigma+ e- nubar and anti-Xi0 --> anti-Sigma+ e+ nu
From 56 days of data taking in 2002, the NA48/1 experiment observed 6316 Xi0
--> Sigma+ e- nubar candidates (with the subsequent Sigma+ --> p pi0 decay) and
555 anti-Xi0 --> anti-Sigma+ e+ nu candidates with background contamination of
215+-44 and 136+-8 events, respectively. From these samples, the branching
ratios BR(Xi0 --> Sigma+ e- nubar)= (2.51+-0.03stat+-0.09syst)E(-4) and
BR(anti-Xi0 --> anti-Sigma+ e+ nu)= (2.55+-0.14stat+-0.10syst)E(-4) were
measured allowing the determination of the CKM matrix element |Vus| =
0.209+0.023-0.028. Using the Particle Data Group average for |Vus| obtained in
semileptonic kaon decays, we measured the ratio g1/f1 = 1.20+-0.05 of the
axial-vector to vector form factors.Comment: 16 pages, 11 figures Submitted to Phys.Lett.
Measurement of the Ratio Gamma(KL -> pi+ pi-)/Gamma(KL -> pi e nu) and Extraction of the CP Violation Parameter |eta+-|
We present a measurement of the ratio of the decay rates Gamma(KL -> pi+
pi-)/Gamma(KL -> pi e nu), denoted as Gamma(K2pi)/Gamma(Ke3). The analysis is
based on data taken during a dedicated run in 1999 by the NA48 experiment at
the CERN SPS. Using a sample of 47000 K2pi and five million Ke3 decays, we find
Gamma(K2pi)/Gamma(Ke3) = (4.835 +- 0.022(stat) +- 0.016(syst)) x 10^-3. From
this we derive the branching ratio of the CP violating decay KL -> pi+ pi- and
the CP violation parameter |eta+-|. Excluding the CP conserving direct photon
emission component KL -> pi+ pi- gamma, we obtain the results BR(KL -> pi+ pi-)
= (1.941 +- 0.019) x 10^-3 and |eta+-| = (2.223 +- 0.012) x 10^-3.Comment: 20 pages, 7 figures, accepted by Phys. Lett.
Measurement of the branching ratio of the decay KL -> pi e nu and extraction of the CKM parameter |Vus|
We present a new measurement of the branching ratio R of the decay KL -> pi e
nu (Ke3), relative to all charged KL decays with two tracks, based on data
taken with the NA48 detector at the CERN SPS. We measure R = 0.4978 +- 0.0035.
From this we derive the Ke3 branching fraction and the weak coupling
parameter |Vus| in the CKM matrix. We obtain |Vus|f+(0) = 0.2146 +- 0.0016,
where f+(0) is the vector form factor in the Ke3 decay.Comment: 18 pages, 8 figures. accepted by Phys Lett.
Measurement of K^0_e3 form factors
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.Comment: 16 pages, 7 figures. submitted to Phys. Lett.
A measurement of the transverse polarization of Lambda-hyperons produced in inelastic pN-reactions at 450 GeV proton energy
A study of the polarization of Λ hyperons produced in inelastic pN reactions induced by the 450 GeV proton beam from the CERN SPS has been performed with the NA48 detector. The Λ hyperons were detected at a fixed angle of 4.2 mrad in the momentum range from 50 GeV/c to 200 GeV/c. The polarization changes from −0.053 ± 0.034 to −0.298 ± 0.074 for a transverse momentum range of the Λ between 0.28 GeV/c and 0.86 GeV/c. The antiΛ polarization is consistent with zero
Direct search for light gluinos
We present the results for a direct search for light gluinos through the appearance of with high transverse momentum in the vacuum tank of the NA48 experiment at CERN. We find one event within a lifetime range of s and another one between s. Both events are consistent with the expected background from neutrons in the beam, produced by 450 GeV protons impinging on the Be targets, which interact with the residual air in the tank. From these data we give limits on the production of the hypothetical bound state, the hadron, and its decay in the mass range between 1 and 5~GeV
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