An energy-independent phase-shift analysis ofπ+p-scattering has been carried out at 16 energies in the region 194–600 MeV. The new data on elastic polarization, obtained in LNPI up to 1983, were included.
No description provided.
No description provided.
No description provided.
We report a new measurement of the differential cross section for π−p→π0n from pπ=649 to 752 MeV/c, which is around the opening of the η channel (685 MeV/c). Our data support the main features of the π−p charge-exchange differential cross sections generated by the SAID πN partial-wave analysis. The opening of the η channel has a clear effect on the shape of the excitation function for dσ(π−p→π0n), which is most noticeable in the backward direction.
Differential cross section for incident pion momentum 649, 654 and 657 MeV.
Differential cross section for incident pion momentum 661, 666 and 669 MeV.
Differential cross section for incident pion momentum 673, 678 and 681 MeV.
Measured values of the differential cross section for pion-nucleon charge exchange are presented at momenta 148, 174, 188, 212, 238, 271, 298, and 323 MeV/c, a region dominated by the Delta resonance. Complete angular distributions were obtained using the Crystal Ball detector at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL). Statistical uncertainties of the differential cross sections are typically 2-6%, exceptions being the results at the lowest momentum and at the most forward measurements of the five lowest momenta. We estimate the systematic uncertainties to be 3-6%.
The errors shown are statistical only.
The errors shown are statistical only.
The total charge-exchange reaction cross section as a function of pion momentum obtained by integrating the differential cross sections. The errors shown are the total and statistical errors.
No description provided.
No description provided.
No description provided.
The ITEP-PNPI collaboration presents the first results of the spin rotation parameter A + measurements in the second resonance region. The experiment was performed at the ITEP accelerator at a positive pion beam momentum 1.43 GeV/c for scattering angles θ cm = 127° and 133°. The setup was based on a polarized proton target and a carbon-plate polarimeter. The obtained data is compared with the predictions of the existing partial-wave analyses.
No description provided.
We report a new measurement of the π−p→3π0n total cross section from threshold to pπ=0.75GeV/c. The cross section near the N(1535)12− resonance is only a few μb after subtracting the large η→3π0 background associated with π−p→ηn. A simple analysis of our data results in the estimated branching fraction B[S11→πN(1440)12+]=(8±2)%. This is the first such estimate obtained with a three-pion production reaction.
Total cross section from threshold to 750 MeV. Only statistical errors are given in the table.
The π − p→K 0 λ polarization has been measured at 5 GeV/ c in the range 0<− t <1.4 (GeV/ c ) 2 . The polarization is small for − t ⪅0.4 (GeV/ c ) 2 , becoming negative at the higher values of − t .
No description provided.
Based on a sample of 22 four-prong D 0 / D 0 decays produced in hydrogen by 360 GeV/ c π − , we present the following new results: mean lifetime τ = (3.5 −0.9 +1.4 ) x 10 −13 s ; production cross section for x F > 0.0, σ = (10.3 ± 3.5) ωb ; the D → K ± π ± π + π − branching ratio = (7.1 ± 2.5)%.
No description provided.
We have analyzed the two-prong final states in π+p interactions at 3.9 GeVc. Our result for elastic scattering is σ (elastic) = 6.50±0.1 mb (statistical error only). We find the elastic slope to be 6.61±0.14 (GeVc)−2. We find the elastic forward cross section to be 40.0±1.4 mb(GeVc)2. We have applied a longitudinal-momentum analysis to the one-pion-production channel. We find the cross section for the reaction π++p→π++π0+p to be 2.30±0.06 mb and that for π++p→π++π++n to be 1.45±0.05 mb. For resonance-production cross sections in these channels we find Δ(1236)=0.60±0.07 mb, ρ(760)=0.86±0.06 mb, and diffraction dissociation = 1.69±0.11 mb. We find that we can satisfactorily fit all distributions in the one-pion-production channel without assuming any phase-space production. In the missing-mass channel we observe dominant Δ++(1236) production plus evidence for A2+ production.
No description provided.
No description provided.
No description provided.
The reaction π−+p→π−+p has been studied in the 15-in. bubble chamber at the Princeton-Pennsylvania Accelerator. The elastic scattering cross section was determined to be 8.5 ± 0.2 mb. The forward peak fits to an exponential in t with a slope of 8.1 ± 0.2 (GeV/c)−2. The forward differential cross section dσdΩ(0)=17.9±0.7 mb/sr. A fit of the center-of-mass angular distribution to Legendre polynomials needed terms up to the 12th order, corresponding to the highest nonzero partial wave of L=6.
No description provided.
FORWARD D(SIG)/DOMEGA IS 17.9 +- 0.7 MB/SR. SLOPE IS 8.1 +- 0.2 GEV**-2 (-T = 0.1 TO 0.4 GEV**2).
OTHER 2.27 GEV/C DATA ALSO QUOTED.
Measurements were made of the cross section of the reactions π − p → ν ′(958)n, η ′ → 2 γ at momenta at 15, 20, 25, 30 and 40 GeV/c. The experiment was carried out on the IHEP 70 GeV accelerator using the 648 channel hodoscope spectrometer NICE for γ-ray detection. A total of 6000 η′ mesons were recorded. A sharp drop is seen in the differential cross section for t → 0. The dependences of the differential cross sections for the π − p → η ′n and π − p → η n on t are identical. On the basis of the ratio of the cross sections for these reactions at t = 0, i.e. R( η′ n ) t=0 = 0.55 ± 0.06 , the singlet-octet mixing angle for pseudoscalar mesons was determined to be β = −(18.2 ± 1.4)°.
DATA AT 20, 25 AND 30 GEV/C SUMMED AND NORMALIZED TO THE CROSS SECTION AT 25 GEV/C.
DATA AT 20, 25 AND 30 GEV/C SUMMED AND NORMALIZED TO THE CROSS SECTION AT 25 GEV/C.
We have studied the reactionspp→ppπ+π-,K+p→K+pπ+π−π, π+p→ π+,pπ+π− and π−p →π+π− at 147 GeV/c using the 30-inch Fermilab hybrid system. All four reactions were detected with the same apparatus and analyzed in the same way. The energy dependence of the channel cross section was found to beAp−0.6+B for thepp reaction andAp−1+B for the other three. About 90% of the cross section at 147 GeV/c can be accounted for by either beam or target diffraction. Some of the remaining cross section may come from double Pomeron exchange reactions which we tried to isolate. We have tested the hypothesis of a factorizable Pomeron and our data indicates a violation of this hypothesis. We show that the 3π mass enhancement in the mass region 1.2–1.4 GeV is diffractively produced in the π± beam reactions. Fourprong, four-constraint and six-prong, four-constraint cross sections are reported.
No description provided.
No description provided.
CROSS SECTIONS FOR DIFFRACTION DISSOCIATION OF BEAM. FEYNMAN X OF OUTGOING PROTON <-0.96.
A study of π − p → K ∗ Λ and π − p → K ∗ Σ° at 3.9 GeV /c indicates that the main features of both reactions can be interpreted in terms of simple exchange processes, the first involving both natural and unnatural exchange, the second showing evidence for natural parity exchange only.
A description is given of an experimental study of exchange degeneracy (EXD) in hypercharge-exchange reactions using the line-reversed partners π + p→K + Σ + (K − p→ π − Σ + ) and π + p→ K + Σ + (1385) (K − p→ π − Σ + (1385)) at incident momenta of 7.0 and 10.1 GeV/ c . Both pairs of reaction were measured in the same apparatus, with particular care being taken to minimize relative normalization errors. For the Σ production reactions we present high statistics measurements of the differential cross sections and polarizations from t ′=0 to large t . The general trends of the data agree with naive expectations from weak EXD. The cross-section difference in the extreme forward direction at the higher momentum is consistent with zero and there is a general reduction in the cross-section differences going from the lower to the higher momentum. The polarizations are approximately equal in magnitude and of opposite sign between the two reactions. On the other hand, the data do not agree with the detailed predictions of EXD. The slope for the positive reaction is systematically steeper in the forward region than for the negative reaction and there is a complex s and t dependence for the cross-section differences including a cross-over at t ⋍ −0.8( GeV /c) 2 . For the Σ(1385) production reactions, we present differential cross-section measurements in the forward region (| t |<0.3(GeV/ c ) 2 ). The cross-section differences are substantial and essentially constant over the s and t ranges studied.
THE RESULTS AT 10.1 GEV WERE FIRST PUBLISHED IN A. BERGLUND ET AL., PL 60B, 117 (1975), THE RECORD OF WHICH INCLUDES THE TABULATED DATA.
We have measured in a single experimental setup the differential cross sections and polarizations of the Y*(1385) produced in the two line-reversed reactions π+p→K+Y*(1385) (260 eV/μb) and K−p→π−Y*(1385) (180 eV/μb) at 11.5 GeV/c. We compare these results to Σ+ production in the same experiment. The data have been derived from a triggered bubble-chamber experiment using the SLAC Hybrid Facility. We find that both helicity-flip-dominated (Y*) and helicity-nonflip-dominated (Σ) processes are consistent with weak-exchange-degeneracy predictions.
Axis error includes +- 10/10 contribution.
Axis error includes +- 10/10 contribution.
Axis error includes +- 10/10 contribution.
The differential cross section for η production in reaction π−p→ηn has been measured over the full angular range at seven incident π− beam momenta from threshold to pπ−=747 MeV/c using the Crystal Ball multiphoton spectrometer. The angular distributions are S wave dominated. At 10 MeV/c above threshold, a small D-wave contribution appears that interferes with the main S wave. The total η production cross section σtot is obtained by integration of dσ/dΩ. Starting at threshold, σtot rises rapidly, as expected for S-wave-dominated production. The features of the π−p→ηn cross section are strikingly similar to those of the SU(3) flavor-related process K−p→ηΛ. Comparison of the π−p→ηn reaction is made with η photoproduction.
Total cross sections.
Differential cross section for the 4 lowest beam momenta.
Differential cross section for the 3 highest beam momenta.
The polarization of the Σ+ has been measured for the line-reversed reactions π+p→K+Σ+ and K−p→π−Σ+ at 7 and 11.6 GeV/c using the SLAC Hybrid Facility. Since the Σ+ decay is observed in the bubble chamber, the trigger of the flash lamps on a fast K+(π−) did not bias the polarization measurements. We find that the Σ+ polarizations from the two reactions have opposite signs but similar magnitudes and are in much better agreement with the predictions of weak exchange degeneracy than previous lower-energy comparisons.
No description provided.
Reaction π−p→π0π0n has been measured with high statistics in the beam momentum range 270–750MeV∕c. The data were obtained using the Crystal Ball multiphoton spectrometer, which has 93% of 4π solid angle coverage. The dynamics of the π−p→π0π0n reaction and the dependence on the beam energy are displayed in total cross sections, Dalitz plots, invariant-mass spectra, and production angular distributions. Special attention is paid to the evaluation of the acceptance that is needed for the precision determination of the total cross section σt(π−p→π0π0n). The energy dependence of σt(π−p→π0π0n) shows a shoulder at the Roper resonance [i.e., the N(1440)12+], and there is also a maximum near the N(1520)32−. It illustrates the importance of these two resonances to the π0π0 production process. The Dalitz plots are highly nonuniform; they indicate that the π0π0n final state is dominantly produced via the π0Δ0(1232) intermediate state. The invariant-mass spectra differ much from the phase-space distributions. The production angular distributions are also different from the isotropic distribution, and their structure depends on the beam energy. For beam momenta above 550MeV∕c, the density distribution in the Dalitz plots strongly depends on the angle of the outgoing dipion system (or equivalently on the neutron angle). The role of the f0(600) meson (also known as the σ) in π0π0n production remains controversial.
Measured total cross section. Statistical errors only.
Differential angular distributions of the 2PI0 system for the LH2 data at beam momenta 355 to 472 MeV/c. Statistical errors only.
Differential angular distributions of the 2PI0 system for the LH2 data at beam momenta 550 to 678 MeV/c. Statistical errors only.
The reaction π − p→ π + π − n has been measured in a high-statistics experiment on a transversely polarized proton target at 17.2 GeV, and unexpectedly large nucleon polarization effects have been observed. Combining the results of this experiment with a measurement on a hydrogen target allows a model-independent partial-wave analysis in terms of the “nucleon transversity” amplitudes. Unique or at most twofold ambiguous solutions are obtained. In particular we find a high lower limit ( ⪆30% ) of the spin non-flip unnatural exchange amplitudes at low | t |. These amplitudes, interpreted as being due to the exchange of an object with the quantum numbers of the A 1 , have been assumed to be absent in previous analyses. In checking the consequences of this finding on the old results, we test the validity of the rank-two assumotions for the density matrix. We find a small but significant deviation, which shows the need for a new phase-shift analysis including the A 1 exchange contribution.
MASS DEPENDENCE OF NORMALIZED T-CHANNEL MOMENTS SCALED TO 100 PCT POLARIZED PROTONS.
T DEPENDENCE OF NORMALIZED T-CHANNEL MOMENTS IN THE RHO REGION SCALED TO 100 PCT POLARIZED PROTONS.
We present the results and the analysis of a high-statistics experiment to study A 2 and g production in the reaction π − p→K − K S 0 p at 10 GeV/ c . In each resonance region we perform a moment analysis of the data, and from the moments we determine the production amplitudes as a function of t . We find A 2 production proceeds dominantly by natural-parity (pomeron and f) exchange. We compare A 2 and diffractive K ∗ (1420) production. We find g production proceeds by π and ω exchanges; we determine the g → K K branching ratio.
No description provided.
No description provided.
Angular distributions for π+p→π+p were measured for 13 incident-pion momenta from 4.4 to 6.0 GeV/c and for −t less than ∼0.1 (GeV/c)2. This experiment was performed at the Zero Gradient Synchrotron of Argonne National Laboratory, where a focusing magnetic spectrometer and a scintillation-counter hodoscope were used. In fitting the angular distributions the strong-interaction contribution was parameterized by an exponential form exp(bt); the Coulomb interference was also included. The resulting values of the slope parameter for |t|<∼0.1 (GeV/c)2 are presented for each incident beam momentum.
SLOPE IS FROM FITTING EXP(SLOPE*T) TO FORWARD DIFFERENTIAL CROSS SECTION FOR -T < 0.1 GEV**2 APPROX AFTER ALLOWING FOR COULOMB INTERACTION.
We have performed the most comprehensive resonance-model fit of $\pi^-\pi^-\pi^+$ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction $\pi^- + p \to \pi^-\pi^-\pi^+ + p_\text{recoil}$ with a 190 GeV/$c$ pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, $0.5 < m_{3\pi} < 2.5$ GeV/$c^2$, and simultaneously in 11 bins of the reduced four-momentum transfer squared, $0.1 < t' < 1.0$ $($GeV$/c)^2$, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with $J^{PC} = 0^{-+}$, $1^{++}$, $2^{++}$, $2^{-+}$, $4^{++}$, and spin-exotic $1^{-+}$ quantum numbers. The model contains the well-known resonances $\pi(1800)$, $a_1(1260)$, $a_2(1320)$, $\pi_2(1670)$, $\pi_2(1880)$, and $a_4(2040)$. In addition, it includes the disputed $\pi_1(1600)$, the excited states $a_1(1640)$, $a_2(1700)$, and $\pi_2(2005)$, as well as the resonancelike $a_1(1420)$. We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 $t'$ bins. We extract the relative branching fractions of the $\rho(770) \pi$ and $f_2(1270) \pi$ decays of $a_2(1320)$ and $a_4(2040)$, where the former one is measured for the first time. In a novel approach, we extract the $t'$ dependence of the intensity of the resonances and of their phases. The $t'$ dependence of the intensities of most resonances differs distinctly from the $t'$ dependence of the nonresonant components. For the first time, we determine the $t'$ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances.
Real and imaginary parts of the normalized transition amplitudes $\mathcal{T}_a$ of the 14 selected partial waves in the 1100 $(m_{3\pi}, t')$ cells (see Eq. (12) in the paper). The wave index $a$ represents the quantum numbers that uniquely define the partial wave. The quantum numbers are given by the shorthand notation $J^{PC} M^\varepsilon [$isobar$] \pi L$. We use this notation to label the transition amplitudes in the column headers. The $m_{3\pi}$ values that are given in the first column correspond to the bin centers. Each of the 100 $m_{3\pi}$ bins is 20 MeV/$c^2$ wide. Since the 11 $t'$ bins are non-equidistant, the lower and upper bounds of each $t'$ bin are given in the column headers. The transition amplitudes define the spin-density matrix elements $\varrho_{ab}$ for waves $a$ and $b$ according to Eq. (18). The spin-density matrix enters the resonance-model fit via Eqs. (33) and (34). The transition amplitudes are normalized via Eqs. (9), (16), and (17) such that the partial-wave intensities $\varrho_{aa} = |\mathcal{T}_a|^2$ are given in units of acceptance-corrected number of events. The relative phase $\Delta\phi_{ab}$ between two waves $a$ and $b$ is given by $\arg(\varrho_{ab}) = \arg(\mathcal{T}_a) - \arg(\mathcal{T}_b)$. Note that only relative phases are well-defined. The phase of the $1^{++}0^+ \rho(770) \pi S$ wave was set to $0^\circ$ so that the corresponding transition amplitudes are real-valued. In the PWA model, some waves are excluded in the region of low $m_{3\pi}$ (see paper and [Phys. Rev. D 95, 032004 (2017)] for a detailed description of the PWA model). For these waves, the transition amplitudes are set to zero. The tables with the covariance matrices of the transition amplitudes for all 1100 $(m_{3\pi}, t')$ cells can be downloaded via the 'Additional Resources' for this table.
Decay phase-space volume $I_{aa}$ for the 14 selected partial waves as a function of $m_{3\pi}$, normalized such that $I_{aa}(m_{3\pi} = 2.5~\text{GeV}/c^2) = 1$. The wave index $a$ represents the quantum numbers that uniquely define the partial wave. The quantum numbers are given by the shorthand notation $J^{PC} M^\varepsilon [$isobar$] \pi L$. We use this notation to label the decay phase-space volume in the column headers. The labels are identical to the ones used in the column headers of the table of the transition amplitudes. $I_{aa}$ is calculated using Monte Carlo integration techniques for fixed $m_{3\pi}$ values, which are given in the first column, in the range from 0.5 to 2.5 GeV/$c^2$ in steps of 10 MeV/$c^2$. The statistical uncertainties given for $I_{aa}$ are due to the finite number of Monte Carlo events. $I_{aa}(m_{3\pi})$ is defined in Eq. (6) in the paper and appears in the resonance model in Eqs. (19) and (20).
None
No description provided.
No description provided.
No description provided.
The production of KS, Λ, Λ¯, and γ in π−p collisions at 147 GeV/c is analyzed. Cross sections, rapidity, Feynman-x, and pT2 distributions are presented and compared to charged-particle production. The energy dependence of multiplicities in π−p and pp collisions is shown. A new scaling form for the correlation of neutral- and charged-particle multiplicities is presented for compilations of πp and pp data.
Axis error includes +- 0.0/0.0 contribution (?////ERRORS QUOTED ARE MAINLY STATISTICAL BUT INCLUDE CONTRIBUTIONS FROM ESTIMATES OF CONTAMINATION AND OF THE RELIABILITY OF WEIGHTING SCHEMES10 PCT OF ALAMBDA EVENTS COULD BE GAMMA CONTAMINATION, 0.5 PCT OF KS EVENTS COULD HAVE BEEN MISCLASSIFIED AS GAMMA'S).
Axis error includes +- 0.0/0.0 contribution (?////ERRORS QUOTED ARE MAINLY STATISTICAL BUT INCLUDE CONTRIBUTIONS FROM ESTIMATES OF CONTAMINATION AND OF THE RELIABILITY OF WEIGHTING SCHEMES10 PCT OF ALAMBDA EVENTS COULD BE GAMMA CONTAMINATION, 0.5 PCT OF KS EVENTS COULD HAVE BEEN MISCLASSIFIED AS GAMMA'S).
In this paper we present the results of an analysis of strange-particle production in π−p collisions leading to two charged final particles and at least one strange neutral decay. The sample consists
No description provided.
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