Search

A partial wave analysis of the centrally produced π 0 π 0 channel has been performed in pp collisions using an incident beam momentum of 450 GeV/c. An unambiguous physical solution has been found. Evidence is found for the f 0 (980), f 0 (1300) and f 0 (1500) in the the S -wave. and the f 2 (1270) is observed dominantly in the D 0 − -wave. In addition, there is evidence for a broad enhancement in the D -wave below 1 GeV.

A study of the reactions pp -> pfps(K+K-pi+pi-) and pp -> pfps(K+K-pi+pi-pi0) shows evidence for the K*K* and phi omega channels respectively. The K*K* mass spectrum shows a broad distribution with a maximum near threshold and an angular analysis shows that it is compatible with having JP = 2+. The behaviour of the cross-section as a function of centre of mass energy, and the four momentum transfer dependence, are compatible with what would be expected if the K*K* system was produced via double Pomeron exchange. The dPT behaviour of the phi omega channel is similar to what has been observed for all the undisputed qqbar states. In contrast, the dPT behaviour of the K*K* final state is similar to what has been observed for the phi phi final state and for previously observed glueball candidates.

A study has been made of pseudoscalar mesons produced centrally in pp interactions. The results show that the eta and etaprime appear to have a similar production mechanism which differs from that of the pi0. The production properties of the eta and etaprime are not consistent with what is expected from double Pomeron exchange. In addition the production mechanism for the eta and etaprime is such that the production cross section are greatest when the azimuthal angle between the pT vectors of the two protons is 90 degrees., 11 pages, Latex, 3 Figures

The reaction pp -> pf (pi+pi-pi0) ps has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dPT filter applied. The analysis confirms the previous observation that all undisputed qqbar states are suppressed at small dPT. In addition, a clear difference is observed in the production mechanism for the eta and omega. The reaction pp → p f ( π + π − π 0 ) p s has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dP T filter applied. The analysis confirms the previous observation that all undisputed q q states are suppressed at small dP T . In addition, a clear difference is observed in the production mechanism for the η and ω . The reaction pp -> pf (pi+pi-pi0) ps has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dPT filter applied. The analysis confirms the previous observation that all undisputed qqbar states are suppressed at small dPT. In addition, a clear difference is observed in the production mechanism for the eta and omega.

The lead tungstate (PWO) heavy crystal calorimeter is tested in a GAMS-type experiment detecting 50 000 π 0 -mesons produced in a 32.5 GeV/ c intensive π − beam of the 70 GeV IHEP accelerator. In spite of a huge beam load of the calorimeter cells (up to 10 6 π − /s), a clean π 0 → 2 γ signal is observed. The measured PWO spectrometer mass resolution is in good accordance with previous electron beam tests and GEANT calculations. A high precision of the real-time PWO spectrometer calibration, using the π 0 signal during the physics run, is achieved. The results of these very first spectrometric beam tests demonstrate a high performance of multicell PWO spectrometers in heavy-load high energy physics experiments of both fixed target and collider types.

Central \pipi events produced in pp interactions are studied in terms of correlations between the outgoing protons. It is observed there is more $\rho^{0}$(770) and \fmeson production in reactions where the outgoing protons %fastest and slowest particles in the laboratory frame are on opposite sides of the beam. This effect is not attributable to the trigger or the experimental acceptance, and suggests that the vertices do not factorise.

A high-statistics study of the π0π0-system produced in the π-p→π0π0n reaction at 38GeV/c has been carried out at the IHEP accelerator using the GAMS-2000 multiphoton spectrometer. A partial-wave analysis which includesS, D0, D− andD+ waves has been performed in the |t|-range up to 1 (GeV/c)2. TheS*/f0(980) resonance is seen as a dip in theS-wave amplitude at small |t|. A distinct peak with a mass of 997±5MeV and a width of 48±10MeV is observed in theS-wave at |t|>0.3 (GeV/c)2. The production cross sections are measured.

A planar version of the BAYAN electromagnetic calorimeter is tested with 10, 25, 50 and 100 GeV electrons at CERN SPS beam. The BAYAN energy resolution shows a very low constant term: σ E E=7.7% E ⊕ 0.2% . In the range E ≥ 100 GeV it drops well below 1%.

Recent results on ωπ0 partial-wave analysis from the GAMS Collaboration are presented. A partial-wave analysis of the 38 GeV/c π-p charge exchange data confirmed the existence of theρ(2200) radial-orbital excitation of theρ(770) ground-state observed earlier in the same experiment. A new 5−− state,π5(2350), was also observed in this analysis. Masses, widths and production cross-sections for these states are given.

Recent results on ωπ0 partial-wave analysis from the GAMS Collaboration are presented. A partial-wave analysis of the 38 GeV/c π-p charge exchange data confirmed the existence of theρ(2200) radial-orbital excitation of theρ(770) ground-state observed earlier in the same experiment. A new 5−− state,π 5(2350), was also observed in this analysis. Masses, widths and production cross-sections for these states are given.

The branching ratio of the rare radiative decay ω→ηγ has been measured: BR(ω→ηγ)=(8.3±2.1)·10−4. The experiment was performed at the IHEP (Serpukhov) accelerator with 38 GeV/c incident pions in the chargeexchange reaction π-p→ωn the photons from the ω→ηγ→3γ decay being detected with the multiphoton spectrometer GAMS-2000. The influence of ω-ρ mixing, which was a source of ambiguity in the interpretation of previous experiments, has been much reduced by measuring the ω produced at large momentum transfer.

The rare ηγ decay width of the ω-meson has been measured in a model-independent way, with ω produced in 38 GeV/c π−p charge-exchange. Large momentum transfer events have been selected in order to eliminate ω-ρ interference contribution. BR (ω→ηγ) =(8.3±2.1)·10−4. The gammas from ω→ηγ→3γ decay have been detected with the multiphoton spectrometer GAMS-2000 at the IHEP 70 GeV proton accelerator.

New data from π-p charge-exchange at 38 GeV/c confirm the existence of the narrow X (1740) meson, observed in its ηη decay mode. The upper limit on its width is 80 MeV. It is not observed decaying into either η′η, or π0π0. This meson is produced in charge-exchange by a mechanism other than OPE with a nucleon isobar (probably Δ(1232)), and not with a neutron., SCOPUS: ar.j, info:eu-repo/semantics/published

The inclusive cross sections of backward proton production in π − ( K − , p ) -Be, Al, Cu, Pb interactions at 40 GeV/ c are presented. Protons have been detected in the angular range 150°–165° and kinetic energy region 0.1–0.3 GeV. The invariant cross-section ratios for various beam particles are independent of the values of kinetic energy and of the nuclear target type: 〈ƒ K − /ƒ π − 〉= 0.87 ± 0.03 stat ± 0.03 syst , 〈ƒ p /ƒ π − 〉 = 1.82 ± 0.10 stat ± 0.05 syst . The A -dependence of the cross-section slope parameter for A ⩾27 is less than ∼2%.

We present results on the production of jets and "jetlike" clusters in 800-GeV/c proton-nucleus (pA ) collisions. Events with high values of transverse energy in the central kinematic region were selected for nuclear targets of H, Be, C, Cu, and Pb. A jet-finding algorithm was used in analyzing the data. The A dependence of the jet and dijet cross sections was parametrized as Aα. The values of α for events with "jetlike" cluster pairs found by the algorithm without any additional kinematic cuts reach a plateau of approximately 1.5 at dijet transverse energies > GeV. The collimation of observed "jetlike" clusters decreases with A, and the fragmentation is softer for heavier target nuclei. However, nuclear effects become less pronounced with the increasing cluster or cluster-pair transverse energy. We argue that the observed nuclear enhancement for the production of "jetlike" clusters is due to underlying event or/and soft-scattering contributions to the heavy-nuclei data. We show that the nuclear enhancement becomes consistent with a value of α within 0.10 from unity once the data are corrected for the underlying event or kinematic cuts enhancing clear jet structure are applied.

The nuclear ({ital A}) dependence of the event structure in the central and forward (projectile fragmentation) regions has been studied for highly inelastic proton-nucleus ({ital pA}) collisions at an incident momentum of 800 GeV/{ital c}. Events with high values of transverse energy ({ital E}{sub {ital t}}) were selected using the large-acceptance Fermilab multiparticle spectrometer. The multiplicity distributions and energy flows in different regions of phase space are presented for six nuclear targets: H, Be, C, Al, Cu, and Pb. The event structure for highly inelastic {ital pA} collisions is strongly dependent on the transverse energy observed in the central region. However at a fixed {ital E}{sub {ital t}}, there is only a weak nuclear dependence of event structure in the central and forward fragmentation regions. This observation is consistent with a thermodynamical description of inelastic {ital pA} interactions and suggests that the observed {ital E}{sub {ital t}} is a good measure of the inelasticity of the reaction. The nuclear dependence of event structure on the particle density and the energy in the forward fragmentation region is also discussed. In contrast with {ital E}{sub {ital t}} as a variable, the particle density and the forward missing energy provide measures of eventmore » inelasticity that are {ital A} dependent.« less

A study of the centrally produced ppbar, ppbarpi, ppbarpipi and lambda lambda channels has been performed in pp collisions using an incident beam momentum of 450 GeV/c. No significant new structures are observed in the mass spectra, however, important new information on the production dynamics is obtained. A systematic study of the production properties of these systems has been performed and it is found that these systems are not produced dominantly by double Pomeron exchange., Comment: 13 pages, Latex, 4 Figures

A partial wave analysis of the centrally produced pi+pi- channel has been performed in pp collisions using an incident beam momentum of 450 GeV/c. An unambiguous physical solution has been found. Evidence is found for the f0(980), f0(1300), f0(1500) and fJ(1710) with J = 0 in the the S-wave. The rho(770) is observed dominantly in the P0-wave and the f2(1270) is observed dominantly in the D0-wave. In addition, there is evidence for a broad enhancement in the D-wave below 1 GeV., Comment: 12 pages, Latex, 4 Figures

A partial wave analysis of the centrally produced K+K- and K0K0 channels has been performed in pp collisions using an incident beam momentum of 450 GeV/c. An unambiguous physical solution has been found in each channel. The striking feature is the observation of peaks in the S-wave corresponding to the f0(1500) and fJ(1710) with J = 0. The D-wave shows evidence for the f2(1270)/a2(1320), the f2(1525) and the f2(2150) but there is no evidence for a statistically significant contribution in the D-wave in the 1.7 GeV mass region., Comment: 15 pages, Latex, 5 Figures

A study of the f1(1285) and f1(1420) produced in central pp interactions has been performed. For the first time in a single experiment the branching fractions of both mesons in all major decay modes have been determined. Both the f1(1285) and f1(1420) are consistent with being produced by double Pomeron exchange., Comment: 15 pages, Latex, 5 Figures, submitted to Physics Letters B

The reaction pp to pfps(K+K-K+K-) in which the K+K-K+K- system is centrally produced has been studied at 450 GeV/c. Phi phi production has been found to dominate this reaction and is compatible with being produced by double Pomeron exchange. An angular analysis of the phi phi system favours JPC = 2++ and its dPT dependence is similar to that observed for glueball candidates., Comment: 11 pages, Latex, 4 Figures

Results are presented of an analysis of the reactions pp -> pf(k0k+pi-)ps and pp -> pf(K0K0pi0)ps at 450 GeV/c. Clear f1(1285) and f1(1420) signals are seen and a spin parity analysis shows that both have IG JPC=0+ 1++. The f1(1285) decays to a0(980)pi and the f1(1420) decays to K* Kbar. Both states have a similar dependence as a function of dPT consistent with what has been observed for other qqbar states. Evidence is also presented for a K*Kbar decay mode of the eta2(1620)., 13 pages, Latex, 4 Figures

The effective mass spectrum of π0 pairs produced in pp central collisions (pp → pfπ0π0ps) at 450 GeV/c, s = 29 GeV , below 1 GeV differs from that observed in peripheral charge exchange reactions. In particular, there is a large number of events between ππ-threshold and 1 GeV, that interfere with f0(980) destructively. The possible existence of a broad S-wave state is suggested.

The reaction pp -> pf (pi+pi-pi+pi-) ps has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dPT filter applied. In addition to the well known f1(1285) there is evidence for two JPC=2-+ states called the eta2(1620) and eta2(1875) and a broad scalar called the f0(2000). The production of these states as a function of the dPT kinematical filter shows the behaviour expected for qqbar states. In contrast, there is evidence for two states at 1.45 GeV and at 1.9 GeV which do not show the behaviour observed for qqbar states. The reaction pp → p f ( π + π − π + π − ) p s has been studied at 450 GeV/c in an experiment designed to search for gl states. A spin analysis has been performed and the dP T filter applied. In addition to the well know f 1 (1285) there is evidence for two J PC = 2 −+ states called the η 2 (1620) and η 2 (1875) and a broad scalar called the f 0 (2000). The production of these states as a function of the dP T kinematical filter shows the behaviour expected for q q states. In contrast, there is evidence for two states at 1.45 GeV and at 1.9 GeV which do not show the behaviour observed for q q states. The reaction pp -> pf (pi+pi-pi+pi-) ps has been studied at 450 GeV/c in an experiment designed to search for gluonic states. A spin analysis has been performed and the dPT filter applied. In addition to the well known f1(1285) there is evidence for two JPC=2-+ states called the eta2(1620) and eta2(1875) and a broad scalar called the f0(2000). The production of these states as a function of the dPT kinematical filter shows the behaviour expected for qqbar states. In contrast, there is evidence for two states at 1.45 GeV and at 1.9 GeV which do not show the behaviour observed for qqbar states.

A study of central meson production as a function of the difference in transverse momentum ($dP_T$) of the exchanged particles shows that undisputed $q \overline q$ mesons are suppressed at small $dP_T$ whereas the glueball candidates are enhanced.

The mass spectra of the ωπ0 system, produced in π-p charge-exchange reactions at 38 GeV/c and 100 GeV/c, show a new neutral state with a mass of 2200±20 MeV and a width of 260±50 MeV. Like ρ3(1690), this meson, X(2200), is produced through one-pion-exchange. X(2200)JPC is likely 1--. It might be a 23D1 radial-orbital excitation of ρ0. Its production cross section falls with energy quadratically, in agreement with one-pion-exchange. The cross sections for b1(1235) and ρ3(1690) production have also been measured; their energy dependences have been determined. © 1992 Springer-Verlag., SCOPUS: ar.j, info:eu-repo/semantics/published

The production of η′π0 system in π-p charge-exchange interactions at π- momenta 38 GeV/c and 100 GeV/c has been studied. The 2γ and ηπ0π0 decay modes of η′ leading to 4γ and 8γ final states respectively have been detected. No statistically significant peak is observed in the η′π0 mass spectrum in the range of 1.2 GeV÷2.1 GeV. An upper limit of 6·10-3 has been established for the a20(1320)→η′π0 branching ratio. © 1992 Springer-Verlag., SCOPUS: ar.j, info:eu-repo/semantics/published

New data on the ν′ν system produced in the π−p charge exchange at 38 GeV c momentum confirm the existence of the narrow ν′ν resonance X(1910). The hypothesis of the X(1910) quantum numbers being a JPC = 1−+, forbidden for the q[ovbar|q] meson, is proposed to explain the extremely low limits obtained for X(1910) decays through π0π0, νν and K0sK0s channels and the flat t-dependence of the X(1910) production cross section.

The reaction π − + p → π − + π − + π + + p at 25 GeV/ c was studied in the mass region M 3 π ⩾ 1.8 GeV with leading π + . The mass spectrum of the π + π − system shows peaks corresponding to the ϱ 0 , f and g 0 resonances and an enhancement around 1.9 GeV. Evidence is presented for a J P = 3 + s-wave g 0 π − state (A 4 ) similar to the ϱ 0 π − (A 1 ) and fπ − (A 3 ) threshold enhancements.

We present the results of an experimental investigation of the production in the nuclear Coulomb field of low-invariant-mass pions pairs by the reaction ..pi../sup -/Z..--> pi../sup -/..pi../sup 0/Z at 40 GeV. We have obtained for the first time the experimental value of the ..gamma -->..3..pi.. coupling constant F/sup 3pi/(0) = 13.0 +- 0.9 +- 1.3 GeV/sup -3/, where the first (second) error is statistical (systematic). This result is in agreement with calculations based on the theory of chiral anomalies.

Invariant mass spectrum of μ + μ − pairs produced by 70 GeV/ c protons in Be target are presented. Distinct enhancements in the mass regions of ϱ, ω mesons, φ meson and J/ψ particle are observed. For J/ψ production x and p ⊥ 2 distributions are given. The total cross section for the reaction p + Be → ( J ψ → μ + μ − ) + … is equal to 9.5 ± 2.5 nb/nucleus .

The vertex ..gamma -->..3..pi.. has been investigated in the reaction of pion pair production by pions in the nuclear Coulomb field, ..pi../sup -/+(Z,A)..--> pi../sup -/+..pi../sup 0/+(Z,A), in the region of low-invariant-mass ..pi../sup -/..pi../sup 0/ pairs. The experiment has been carried out in the 40-GeV pion beam of the IHEP accelerator (Serpukhov) with the SIGMA spectrometer. We have measured for the first time the cross section of the reaction in the region of momentum transfer squared q/sup 2/ ..3..pi.. coupling constant F/sup 3//sup ..pi../ = 12.9 +- 0.9 +- 0.5 GeV/sup -3/, where the first (second) error is statistical (systematic). The obtained result agrees with the calculations based on the Wess-Zumino-Witten effective Lagrangian. The hypothesis of chiral anomalies and the color-SU(3) quark symmetry are confirmed.

The paper presents the results on differential cross sections for elastic scattering of 7+-, K+-mesons and protons on protons in the 4-momentum transfer squared range 0·08 ≦¦t¦≦ ≦1·0 (GeV/c)2 and incident particle momentum of 29 and 43 GeV/c for pions and kaons and 29, 43, 50 and 65 GeV/c for protons. The measurements were taken with the spectrometer Sigma, installed in the positive beam of the IHEP accelerator.

About 7 × 10 3 events of Compton effect on pion in the reaction π − A → A π − γ st 40 GeV/ c were detected and for the first time the charged pion polarizability was obtained α π = (6.8 ± 1.4) × 10 −43 cm 3 .

Propertiea of eventa produced with high values of transverse energy (Et) in 800 GeV/c proton-nucleus collieions are presented. Both full-arimuth and limited aperture high Et triggers were wed to melect event6 from six targets (H, Be, C, Al, Cu, and Pb). The events were collected using the large acceptance Fermilab multiparticle spectrometer that recorded almost 95% of the incoming beam energy. The A dependence of the crow sectiona at a given Rt W(UI parameterixed M Aa . The value of a increases from 0.7 at low Et to a plateau at high Et of approximately 1.6. The high Et value of a is slightly amaller for the limited aperture triggers. A strong dependence of (1 on the event structure was observed; yet-like” events exhibit an A dependence consistent with a-1.0, while for more isotropic events a ia much larger. This observation is consistent with the expected behavior for jet production in pA colliaione. (a) Present address: Dept. of Physics, University of Michigan-Flint, Flint, MI 48502 (*) Present address: Inst. of Nucl. Physics, Novi Sad, Yugoslavia cc) Present address: Dept. of Physics, Univ. of Ariaona, Tucson AZ 85721 cd) Present address: A T & T Bell Laboratories, Naperville, IL, 80540 cc) Present address: Fermi National laboratory, Batavia, IL 60510 (f) Present address: Dept. of Physics, Univ. of Roeheater, NY 14267 (g) Present address: Tata Inst. of Fundamental Research, Bombay, India 400005

The ππ0 production in nuclear Coulomb field at threshold has been studied for the first time experimentally. The cross section of the reaction $$\pi ^ - + (A,Z) \to \pi ^ - + \pi ^0 + (A,Z)$$ at 40 GeV on C, Al, Fe nuclei has been determined for small 4-momentum transferst

The reaction π−A→Aπ− γ at 40 GeV/c was studied on “Sigma” spectrometer on six different nuclear targets in the region of four-momentum transfer |t

In the reaction of π- dissociation into a μ+μ-π- system on a Cu nucleus, a clear enhancement in the ρ0π- effective-mass distribution has been observed in the π2(1680) region. Partial-wave analysis shows that this enhancement is due to the P-wave and has a resonant nature. Coherent and incoherent cross-sections for this enhancement have been measured.

The pion radiative scattering πZ→πZγ at 40 GeV was investigated. Coulomb scattering-i.e. pion Compton-effect-dominates for small fourmomentum transfers in this reaction. In our previous paper we found the pion polarizability to beβ π =(−6.8±1.4)·10−43, cm3, where we assume following the theory that the sum of electrical and magnetic polarizabilities (α π +β π )≃0. More complete analysis of our data is done in order to test this assumption. The result for (α π +β π ) is in agreement with theoretical predictions.

The A -dependence of J/ψ inclusive production by 43 GeV/ c π − -mesons was measured to be σ = (18 ± 6) A (0.92±0.06) nb/nucleus for x > 0.

In the diffraction dissociation of π− into μ+μ−π− on a Cu nucleus at 50 GeV/c, the cross section $$\sigma _{\mu ^ + \mu ^ - \pi ^ - } $$ for the 1+S(ρ0π) wave was measured. The branching ratio of ρ0→μ+μ− could be calculated from the ratio of this and the corresponding cross sections in the diffraction dissociation of π− into π+π−π−. The obtained value $$BR_{\rho ^0 \to \mu ^ + \mu ^ - } = (4.6 \pm 0.2_{stat^ \pm } \pm 0.2_{syst} )10^{ - 5} $$ is in good agreement with the branching ratio $$BR_{\rho ^0 \to e^ + e^ - } $$ , as expected ifeμ universality holds.

Results of the experimental study of inclusive φ meson production off berillium nuclei by 70 GeV/ c protons in the beam fragmentation region x > 0.41 are presented. Fitting of the measured differential cross sections to the forms d σ d x ∼ (1 − x) n x and d σ d p 2 t ∼ exp (−bp 2 t ) gives the parameters n = 6.0 ± 1.7 and b = (2.4 ± 0.7) (GeV/ c ) −2 . In the framework of a quark-parton model the measured φ meson x -distribution suggests that in the region of x > 0.41 nearly 90% of the φ mesons are produced via a strange sea quark fusion. The ratio of the OZI-forbidden and OZI-allowed transition coupling constants has been found to be ten times smaller than the same ratio calculated from the partial decay widths. The total inclusive cross section is estimated to be σ (pN → φ X) = (0.7 ± 0.2) × 10 −27 cm 2 .

The E672/E706 Spectrometer, located in the MW beam at Fermilab, was used to collect data on events containing a pair of muons in the final state with large effective mass. The momentum of incident pions and protons was 530 GeV/c. Nuclear targets included Be, C, Al, Cu and Pb. We report on a preliminary measurement of the A‐dependence of the per nucleus cross section for forward J/ψ production. The apparatus also detected charged particles and γ’s produced in association with the muon pair. The expected physics results on the hadroproduction of χ states and beauty particles are discussed.

The differential cross sections d σ d x and d σ d p t 2 of inclusive J/ψ production by 43 GeV/ c π − off Be, Cu and W nuclei have been measured. Fitting d σ d p t 2 ∼ A α (p t 2 ) we observed the increase of α with p t 2 .