Using the ARGUS detector at DORIS, we have observed the production of F ± mesons in e + e − annihilation at a centre of mass energy of 10 GeV through their subsequent decays into φπ ± and φπ + π − π ± . The values obtained for [ R (e + e − →FX). Branching Ratio] are (1.47 ± 0.32 ± 0.20)% and (1.63 ± 0.42 ± 0.41)% respectively. The observed mass is (1973.6 ± 2.6 ± 3.0) MeV c 2 . The F momentum spectrum is as expected for the fragmentation of c quarks into charmed mesons, but is somewhat softer than for fragmentation into D ∗ mesons. The relevant angular distributions are consistent with a spin-zero assignment of the F meson.
RESULTS OF FITS FOR SPECIFIED DECAY CHANNELS.
ACCEPTANCE CORRECTED FRAGMENTATION FUNCTION FOR THE TWO DECAY CHANNELS COMBINED. X IS PF/PMAX. DATA HAVE BEEN READ FROM THE GRAPH.
Using the ARGUS detector at DORIS we have obtained evidence for a resonance which decays into an F meson and a photon. The observed mass is 2109 ± 9 ± 7 MeV, which is 144 ± 9 ± 7 MeV greater than the F meson mass. Its properties are consistent with those of the F ∗ meson with J P = 1 − .
No description provided.
New data for the reaction e + e − →ϒ(9.46) have been obtained using the DASP detector at the DORIS storage ring. The electronic width Γ ee is (1.5±0.4) keV. The branching ratio for the decay into muon pairs is (2.5 ± 2.1)%. Energy spectra for inclusive production of hadrons are given.
VISIBLE HADRONIC TOTAL CROSS SECTION.
INVARIANT INCLUSIVE PRODUCTION CROSS SECTION E*D3(SIG)/DP**3 BOTH ON AND OFF THE UPSILON(9.46) RESONANCE. NO SIGNIFICANT DIFFERENCE IN EXPONENTIAL SLOPE AS A FUNCTION OF PARTICLE ENERGY E(P=3).
Results on hyperon production are reported for data accumulated at 10 GeV centre-of-mass energy with the ARGUS detector. Signals for both the octet states Λ, Σ 0 and Ξ − and the decuplet states Σ ± (1385), Ξ 0 (1530) and Ω − are observed 1 (references to a specific state are to be interpreted as also implying the charge conjugate state), some for the first time in e + e − annihilation. Baryon rates from γ dir (1S) decays are enhanced by a factor of about 3 over the continuum.
No description provided.
No description provided.
The final state K + K − π + π − has been studied in γγ interactions using the ARGUS detector at the e + e − storage ring DORIS II at DESY. Production of the vector meson pair K ∗0 (892) K ∗0 (892) is observed for the first time. The cross section for K + K − π + π − , K ∗0 K − π + +c.c. and K ∗0 K ∗0 are all found to be of the order of a few nb. In the W γγ range accessible, a mean upper limit of 0.5 nb at 95% CL is derived for φϱ 0 production.
TOPOLOGICAL CROSS SECTION.
(K*0 K*BAR0) cross section.
(K*0 K- PI+ + CC) CROSS SECTION WITH (K*0 K*BAR0) REMOVED.
A study is presented of the inclusive production cross sections of K ∗± (892) vector mesons in pp interactions at 12 and 24 GeV/ c and in π + p interactions at 16 GeV/ c . The K ∗± inclusive cross section is ∼0.9 mb for both pp at 24 GeV/ c and π + p interactions at 16 GeV/ c . For pp interactions, σ( K ∗+ ) and σ( K ∗− ) are seen to rise with energy, showing a threshold behaviour. In both pp and π + p interactions, σ( K ∗+ ) largely exceeds σ( K ∗− ) at these energies and this excess is interpreted as K ∗+ production by beam and target fragmentations. The decays of K ∗±0 yield ∼30% of the K 0 observed in the final states. The p T 2 dependence of both K ∗+ and K ∗ − cross sections is described by an exponential with slope of ∼3.3 (GeV/ c ) −2 . The longitudinal momentum spectra for K ∗+ in 16 GeV/ c π + p and 24 GeV/ c pp interactions are similar in shape in the target hemisphere. The K ∗− spectra are similar over the whole kinematic region when viewed in the quark c.m.s. and point to a central production mechanism. Comparing K ∗+ and ρ 0 production, striking similarities are found.
No description provided.
ASSUMED SIG(KS)=SIG(KL).
No description provided.
The production of η(550) and ω(780) mesons is studied in π ± p interactions at 16 GeV/ c and K − p interactions at 10 and 16 GeV/ c . Cross sections for exclusive channels are presented, and for the π + p data differential cross sections are given for quasi-inclusive production where the η or ω is required to be accompanied by charged particles only. Close similarities are observed between η, ω and also ϱ 0 (770) production in terms of longitudinal and transverse variables. By a rough estimate, the η, ω and ϱ 0 inclusive yields are found to be in the ratio 0.32 : 0.85 : 1, respectively, for 16 GeV/ c π + p collisions. For non-peripheral production we estimate this same ratio to be 0.34 : 0.9 : 1.
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
DATA SUPPLIED BY A.A. LEBEDEV.
The production cross sections for the Λ, Σ0, Ξ−, Σ0 (1385), Ξ0 (1530) and Ω− hyperons have been measured, both in the continuum and in direct ϒ decays. Baryon rates in direct ϒ decays are enhanced by a factor of 2.5 or more compared to the continuum. Such a large baryon enhancement cannot be explained by standard fragmentation models. The strangeness suppression for baryons and mesons turns out to be the same. A strong suppression of spin 3/2 states is observed.
Hyperon rates per multihadronic event in direct UPSILON decays.
Hyperon rates per multihadronic event in the continuum.
LAMBDA spectrum (1/SIG(had))*D(SIG)/D(X) for UPSILON (1S) direct decays, with X = P/Pmax.
The reaction γγ→K + K − π + π − π 0 has been observed for the first time, using the ARGUS detector at the e + e − storage ring DORIS II at DESY. The cross section shows an enhancement for W γγ close to 3 GeV/ c 2 . Searches for γγ→ωφ and for γγ→φφ leading to this final state, as well as for γγ→φφ→2K + 2K − , have been performed. The derived upper limits for ωφ and φφ production are compatible with q q q q model predictions.
TOPOLOGICAL CROSS SECTION.
95 PCT CL UPPER LIMITS.
We report the first direct observation of B meson decays into Λ c + baryons using the decay channel Λ c + → pK − π + . The product of branching ratios Br(B→Λ c + X)·Br(Λ c + →pK − π + = (0.30±0.12±0.06)% is derived from an observed signal of 208±89 events. Using previous measurements of inclusive baryon rates we find a branching ratio for Λ c + → pK − π + of (4.1±2.4)%. The measured Λ c + momentum spectrum indicates that the multi-particle final states dominate the decay B→Λ c + X.
ACCEPTANCE CORRECTED.
Using the ARGUS detector at DORIS, we observe the production of D ∗+ s mesons in e + e − annihilation through their subsequent decays to a D + s and a photon. Photons which convert in the beam pipe or drift chamber inner wall are used to obtain a high precision measurement of the D ∗+ s -D + s mass difference, while photons detected in the shower counters are used to determine the production cross section, and to provide an independent measurement of the D ∗+ s -D + s mass difference. The observed D ∗+ s - D + s mass difference is 142.5±0.8±1.5 MeV/ c 2 , and σ(e + e − →D ∗+ s X)·BR(D ∗+ s →D + s γ)(·BR(D + s →φπ + ) is 4.4±1.1±1.0 pb at 10.2 GeV. The width of the D ∗+ s is less than 4.5 MeV/ c 2 at 90% confidence level.
Cross sections uncorrected for branching ratios.
We report the first observation of an orbitally excited baryon, the Λ(1520), in quark and gluon fragmentation. The production rate is found to be (1.15±0.21±0.16)×10 −2 and (0.80±0.17 −0.13 +0.10 )×10 −2 Λ (1520) hyperons per event in direct ϒ decays and in the continuum, respectively. In contrast to the observed situation for ground state baryons, the production of the Λ(1520) in direct ϒ decays shows little or no enhancement with respect to continuum production.
Full X range uses extrapolation from fit to dsig/dz distribution.
No description provided.
UPSI(1S) DECAYS.
The final states K S 0 K S 0 π + π − and K S 0 K ∓ π 0 π ± , produced in two-photon reactions, have been studied using the ARGUS detector at the e + e − storage ring DORIS II at DESY. The reaction γγ→ K ∗+ K ∗− has been observed for the first time. Its cross section is about eight times larger than that for γγ→ K ∗0 K ∗0 , but it has a similar W γγ dependence.
No description provided.
Topological cross section.
Topological cross section.
Using the ARGUS detector at DORIS II, we have studied the production of the charmed baryon Λ c in e + e − annihilation at centre-of-mass energies near 10 GeV. The Λ c + was seen in the three decay modes pK − π + , Λπ + π − π + and K̄ 0 p, with products of normalized cross section times branching ratio [ R ·Br] of (10.8±1.4±1.2)×10 −3 , 6.6±1.5±0.9)×10 −3 and (6.7±1.4±0.8)×10 −3 respectively. The measured mass for the Λ c was (2283.1±1.7±2.0) MeV/ c 2 . A limit on the decay rates to Λπ + is reported. The fragmentation function of the Λ c was measured.
Data requested from authors.
No description provided.
Using the ARGUS detector at thee+e− storage ring DORIS II, we have investigated inclusive production of π±,K±,Ks0 and\(\bar p\) in multihadron events at 9.98 GeV and in direct decays of the ϒ(1S) meson, i.e. from quark and gluon fragmentation. The most pronounced difference is the rate of baryon production. The Lund Monte Carlo program gives a reasonable qualitative description, although it cannot reproduce our data in detail.
No description provided.
No description provided.
No description provided.
Two-photon production of the exclusive final statesp\(\bar p\)+nπ (n=0, 1, 2, and 3) has been investigated using the ARGUS detector at thee+e− storage ring DORIS II at DESY. The reactionsγγ→p\(\bar p\)π andγγ→p\(\bar p\)π+π−π0 have been observed for the first time, as have theΔ++ and\(\overline {\Delta ^{ ++ } } \) baryons in the final statep\(\bar p\)π+π−. No evidence was found forΔ++\(\overline {\Delta ^{ ++ } } \) production. Topological cross sections for two-photon production ofp\(\bar p\),p\(\bar p\)π0,p\(\bar p\)π+π− andp\(\bar p\)π+π−π0, as well as the crosssection forγγ→Δ++\(\bar p\)π+π−+c.c., have been measured. Upper limits are given for the cross section forγγ→Δ0\(\overline {\Delta ^0 } \),γγ→Δ++\(\overline {\Delta ^{ ++ } } \) andγγ→Λ\(\bar \Lambda \).
Data read from graph.. Additional overall systematic error 13% not included.
Data read from graph.. Additional overall systematic error 13% not included.
Data read from graph.. Additional overall systematic error 13% not included.
Three- and four-body final states with strange particles are studied in π + p and π − p interactions at 16 GeV/ c . We present cross sections and investigate their energy dependence. Production mechanism, resonance production and quantum number transfer are discussed. Strong Y ∗ (1385) production is found in the reaction π + p → Λ K + π + , while the corresponding π − p reaction is dominated by production of K ∗ (890). In the NK K π channels, the K and K are produced mainly at the same vertex, i.e. non-strangeness exchange ΔS = 0 is dominant (about 75% of the cases), whereas in the Λ K ππ channels, the Λ and K are more frequently produced at opposite vertices, i.e. | ΔS | = 1 exchange is important (about 60% of the cases). Results on the polarization of the lambdas produced in the π + p reactions are given.
No description provided.
In a selected sample of 6770 charged current (CC) events of νp interactions with 〈 E ν 〉 = 43 GeV and 〈W〉 = 4.6 GeV , 359 K 0 , 180 Λ and 13 Λ have been observed, which corresponds to a corrected production rate at least one neutral strange particle in (17.4±0.8)% of the CC events. The ratio of the inclusive Λ to K 0 production cross section is found to be 0.26±0.03. The number of CC events containing at least one K 0 increases with increasing E ν and Q 2 , while the CC events containing at least one Λ remain practically constant. The fractions of the total hadronic energy carried by K 0 and Λ are found to be approximately the same in νp as in ep and μp interactions. In the hadronic c.m.s., the K 0 are produced mostly forwards, the Λ mostly backwards, with asymmetry parameters of +0.32±0.02 and −0.45±0.06, respectively. The total strange particle production cross section is estimated to be (25±4)% of the cross section for production of CC events with W >1.5 GeV and that for charm production (10±2)% of the CC cross section well above charm threshold ( W >3 GeV). The production of the resonances K ∗+ (890) and Σ + (1385) has been observed. The production rate of K ∗+ (890) is comparable to that of D ∗+ (2009), above the corresponding thresholds.
No description provided.
Cross-section values or upper limits are presented for twenty-five two-body hypercharge-exchange reactions in K − p and π + p interactions at 10 and 16 GeV/ c . The 16 GeV/ c results are compared with some predictions of line-reversal plus exchange-degenerate Regge poles, of SU(3) and of the additive quark model. Agreement is found in all cases.
No description provided.
Neutral kaon to negative pion production ratios fromvp and\(\bar vp\) charged current interactions in BEBC are presented and compared with LUND fragmentation model predictions. Good agreement is obtained with a strangeness suppression factor λ=0.203±0.014(stat)±0.010(sys). No evidence is seen for an energy dependence of λ in our kinematic region.
No description provided.
No description provided.
Using the UA5 detector, the inclusive central production of Ks<sup loc="post">0</sup> and K<sup loc="post">±</sup> mesons has been measured in non-single-diffractive interactions at the CERN SPS <math altimg="si1.gif"><ovl type="bar" style="s">p</ovl>p</math> Collider at a c.m. energy of 540 GeV. The average transverse momentum is found to be 〈pT〉 = 0.57±0.03 GeV/c in the rapidity range |y|<2.5, which is an increase of about 30% over the top ISR energy. The K/π ratio has increased from about 8% at ISR energies to 9.5±0.9±0.7% (the last error is systematic) at 540 GeV. The average number of Ks<sup loc="post">0</sup> per non-single-diffractive event is 1.1±0.1 and the inclusive inelastic cross section is estimated at 49±5 mb.
No description provided.
No description provided.
No description provided.
Baryon resonance production in quasi-two-body reactions has been studied for the channels K + p→K°p π + , K + n π + and K + p π ° at beam momenta of 2.53, 2.76 and 3.20 GeV/ c . The production cross sections, four-momentum transfer distributions and density matrix elements are given for the Δ(1236), N ∗ (1400), N ∗ (1500) and N ∗ (1680) states. The reaction K + p→K° Δ ++ (1236) is compared to the line reversed reaction K − n → K °Δ − and the charge-exchange SU(3) sum rule for pseudo-scalar meson plus Δ(1236) is tested.
No description provided.
No description provided.
No description provided.
InclusiveKs0, Λ and\(\bar \Lambda\)-production has been investigated in\(\bar p\)p-interactions at 22.4 GeV/c. Total and topological cross sections and multiplicity characteristics of neutral strange particles have been determined. DifferentialKs0 and Λ-cross sections and also characteristics of annihilation processes with neutral kaon production have been studied. It is shown that the difference of the shapes of the invariantx-distributions forK-mesons in the fragmentation region for annihilation and non-annihilation processes can be described in the framework of the “dual” valon model, but not by considering the current (undressed) quark recombination mechanisms only. The polarization of Λ and\(\bar \Lambda\)-hyperons has been measured.
No description provided.
No description provided.
No description provided.
Inclusive and semi-inclusive production of Λ and\(\bar \Lambda\) inK+p interactions is studied at an incident momentum of 70 GeV/c. Cross sections and single particle distributions are presented and compared with data at lower energies. Scaling is observed between 32 and 70 GeV/c in the Feynmanx variable in the target and the beam fragmentation regions for Λ and\(\bar \Lambda\) inclusive production respectively. An increase of Λ (\(\bar \Lambda\)) production is observed in the beam (target) fragmentation regions, whereas the data at 70 and 32 GeV/c are reasonably close in the central region. The dependence of the Λ(\(\bar \Lambda\)) polarization as a function ofx is measured and found to be in general agreement with the results at 32 GeV/c. The (Λ\(\bar \Lambda\)) pair production cross section increases significantly from 32 to 70 GeV/c. The Λ and\(\bar \Lambda\) production associated with an identified proton is also studied.
No description provided.
No description provided.
No description provided.
The inclusive production of π± andK± mesons and of protons and antiprotons ine+e− annihilation has been measured at c.m. energies ofW=14, 22 and 34GeV. Using time of flight measurements and Cerenkov counters the full momentum range has been covered. Differential cross sections and total particle yields are given. At particle momenta of 0.4 GeV/c more than 90% of the charged hadrons are pions. With increasing momentum the fraction of pions among the charged hadrons decreases. AtW=34 GeV and a momentum of 5 GeV/c the particle fractions are approximately π±:K±:p,\(\bar p = 0.55:0.3:0.15\). On average an event atW=34 GeV contains 10.3±0.4π±, 2.0±0.2K± and 0.8±0.1p,\(\bar p\). In addition, we present results on baryon correlations using a sample of events where two or more protons and/or antiprotons are observed in the final state.
No description provided.
No description provided.
No description provided.
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