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SELEX Collaboration

Publications and source records attributed to SELEX Collaboration.

13 recordsLinked to original sources
arXiv2015

The transverse momentum dependence of charged kaon Bose-Einstein correlations in the SELEX experiment

We report on the measurement of the one-dimensional charged kaon correlation functions using 600~GeV/{\it c} $\Sigma^-$, $\pi^-$ and 540~GeV/{\it c} $p$ beams from the SELEX~(E781) experiment at the Fermilab Tevatron. $K^{\pm}K^{\pm}$ correlation functions are studied for three transverse pair momentum, $k_T$, ranges and parameterized by a Gaussian form. The emission source radii, $R$, and the correlation strength, $\lambda$, are extracted. The analysis shows a decrease of the source radii with increasing kaon transverse pair momentum for all beam types.

hep-ex↗
arXiv2008

First Observation of the Cabibbo-suppressed Decays Xi_c+ -> Sigma+ pi- pi+ and Xi_c+ -> Sigma- pi+ pi+ and Measurement of their Branching Ratios

We report the first observation of two Cabibbo-suppressed decay modes, Xi_c+ -> Sigma+ pi- pi+ and Xi_c+ -> Sigma- pi+ pi+. We observe 59+/-14 over a background of 87, and 22+/-8 over a background of 13 events, respectively, for the signals. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600GeV/c Sigma- beam. The branching ratios of the decays relative to the Cabibbo--favored Xi_c+ -> Xi- pi+ pi+ are measured to be B(Xi_c+ -> Sigma+ pi- pi+)/B(Xi_c+ -> Xi- pi+ pi+) = 0.48+/-0.20, and B(Xi_c+ -> Sigma- pi+ pi+)/B(Xi_c+ -> Xi- pi+ pi+) = 0.18+/-0.09, respectively. We also report branching ratios for the same decay modes of the Lambda_c+ relative to Lambda_c+ -> p K- pi+.

hep-ex↗
arXiv2007

Polarization of Lambda0 and antiLambda0 inclusively produced by 610GeV/c Sigma- and 525GeV/c proton beams

We have measured the polarization of Lambda0 and antiLambda0 inclusively produced by 610GeV/c Sigma- and 525GeV/c proton beams in the experiment SELEX during the 1996/7 fixed target run at Fermilab. The polarization was measured as a function of the Lambda longitudinal momentum fraction xF and transverse momentum pt. For the Lambda0 produced by Sigma- the polarization is increasing with xF, from slightly negative at x_F~0 to about 15% at large xF; it shows a non-monotonic behavior as a function of pt. For the proton beam, the Lambda0 polarization is negative and decreasing as a function of xF and pt. The antiLambda0 polarization is compatible with 0 for both beam particles over the full kinematic range. The target dependence was examined but no statistically significant difference was found.

hep-ex↗
arXiv2007

Measurement of the Omega_c^0 lifetime

We report a precise measurement of the Omega_c^0 lifetime. The data were taken by the SELEX (E781) experiment using 600 GeV/c Sigma-, pi- and p beams. The measurement has been made using 83+/-19 reconstructed Omega_c^0 in the Omega- pi- pi+ pi+ and Omega- pi+ decay modes. The lifetime of the Omega_c^0 is measured to be 65 +/- 13(stat) +/- 9(sys) fs.

hep-ex↗
arXiv2002

First Observation of a Family of Double-Charm Baryons

The SELEX experiment (E781) at Fermilab has candidates for high mass states decaying to Lambda_c+ K- pi+ and Lambda_c+ K- pi+ pi+, Cabibbo-allowed decay modes of doubly-charmed baryons Xi_cc+ and Xi_cc++. The masses are consistent with theoretical considerations, but the spectroscopy is surprising. Limited lifetime information suggests that tau_{Xi_cc++} \sim tau_{Xi_cc+}.

hep-ex↗
arXiv2001

Measurement of the Sigma^- Charge Radius by Sigma^- Electron Elastic Scattering

The Sigma^- mean squared charge radius has been measured in the space-like Q^2 range 0.035-0.105 GeV^2/c^2 by elastic scattering of a Sigma^- beam off atomic electrons. The measurement was performed with the SELEX (E781) spectrometer using the Fermilab hyperon beam at a mean energy of 610 GeV/c. We obtain = (0.61 +/- 0.12 (stat.) +/- 0.09 (syst.)) fm^2. The proton and pi^- charge radii were measured as well and are consistent with results of other experiments. Our result agrees with the recently measured strong interaction radius of the Sigma^-.

hep-ex↗
arXiv2001

Hadronic Production of Lambda_c from 600 GeV/c pion, sigma and proton beams

We present data from Fermilab experiment E781 (SELEX) on the hadroproduction asymmetry for anti-Lambda_c compared to Lambda_c+ as a function of xF and pt2 distributions for Lambda_c+. These data were measured in the same apparatus using incident pi-, sigma- beams at 600 GeV/c and proton beam at 540 GeV/c. The asymmetry is studied as a function of xF. In the forward hemisphere with xF >= 0.2 both baryon beams exhibit very strong preference for producing charm baryons rather than charm antibaryons, while the pion beam asymmetry is much smaller. In this energy regime the results show that beam fragments play a major role in the kinematics of Lambda_c formation, as suggested by the leading quark picture.

hep-ex↗
arXiv2000

Recent Results on Charm and Hyperon Physics from SELEX

The SELEX experiment (Fermilab E781) is a 3-stage magnetic spectrometer for the study of charm hadroproduction at large x_F using 600GeV/c Sigma-, pi-, and p beams. New precise measurements of the Lambda_c, D0, and Ds lifetimes are presented. Results on Lambda_c and D_s production for x_F>0.2 are reported as well. The spectrometer was also used for hyperon physics, where we will show measurements of the Sigma- charge radius, the polarization of inclusive produced Lambda's, and the polarization of beam Sigma+.

hep-ex↗
arXiv2000

Recent results from SELEX

Preliminary results on asymmetry for Lc produced by Sigma-,pi- and p beams at xf>0.2 and precise measurements of the Lc,D0 and Ds lifetimes are presented.

hep-ex↗
arXiv1999

Observation of the Cabibbo-suppressed decay Xi_c+ -> p K- pi+

We report the first observation of the Cabibbo-suppressed charm baryon decay Xi_c+ -> p K- pi+. We observe 150 +- 22 events for the signal. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Sigma- beam. The branching fractions of the decay relative to the Cabibbo-favored Xi_c+ -> Sigma+ K- pi+ and Xi_c+ -> X- pi+ pi+ are measured to be B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> Sigma+ K- pi+) = 0.22 +- 0.06 +- 0.03 and B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> X- pi+ pi+) = 0.20 +- 0.04 +- 0.02, respectively.

hep-ex↗
arXiv1999

First Charm Baryon Physics from SELEX (E781)

We present preliminary results on various aspects of charm baryon studies at the 1996-1997 fixed target experiment of Fermilab studying charm produced from incident Sigma, proton, and pion beams at 600 GeV. First results include the comparison of hadroproduction asymmetries for $Lambda_c^+$ production from the 3 beams as well x_F distributions and the first observation of the Cabbibo-suppressed decay $Ξ_c^+ \to p K^- π^+$. The relative branching fraction of the Cabbibo-suppressed mode to the 3-body Cabbibo-favored modes is also presented.

hep-ex↗
arXiv1998

First Charm Hadroproduction Results from SELEX

The SELEX experiment (E781) at Fermilab is a 3-stage magnetic spectrometer for the high statistics study of charm hadroproduction out to large x_F using 600 GeV Sigma^-, p and pi beams. The main features of the spectrometer are: high precision silicon vertex system, broad-coverage particle identification with TRD and RICH, 3-stage lead glass photon detector. Preliminary results on differences in hadroproduction characteristics of charm mesons and Lambda_c^+ for x_F>0.3 are reported. For baryon beams there is a striking asymmetry in the production of baryons compared to antibaryons. Leading particle effects for all incident hadrons are discussed.

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