Isobar channels and nucleon resonances in π + π − electroproduction on protons

Acomprehensive set of differential cross sections for the reaction γ _ν p → π ^? π ⁺ p at the square of the photon 4-momentum in the range 0.2 < Q ² < 0.6 GeV² and the invariant mass of final-state hadrons in the range 1.3 < W < 1.6 GeV was first obtained with the CLAS detector at the Thomas Jefferson Laboratory. An analysis of these data on the basis of the phenomenological model developed by physicists from the Institute of Nuclear Physics at Moscow State University (INP MSU) and Thomas Jefferson Laboratory (INP MSU-Hall B at Jefferson Lab Collaboration) made it possible to determine, for the first time, the contributions of all isobar channels to the differential cross sections in question. The possibility of extracting the Q ² dependences of the electromagnetic form factors for the P ₁₁(1440) and D ₁₃(1520) resonances in a kinematical region that is the most sensitive to the contribution of the meson-baryon cloud to the structure of nucleon resonances is demonstrated.     

About radiative kaon decay K + → π + π 0 γ

With usage of the Low theorem, the general expression for the amplitude of radiative kaon decay K ⁺ → π ⁺ π ⁰ γ is determined. The possible reason of suppression for the branching ratio of kaon decay K ⁺ → π ⁺ π ⁰ is considered. The text was submittedby the authors in English.     

π+p and K+p elastic scattering at 250 GeV/c

Results are presented on π⁺p and K⁺p elastic scattering at 250 GeV/c, the highest momentum so far reached for positive meson beams. The experiment (NA22) was performed with the european hybrid spectrometer. The π⁺p elastic cross section stays constant with energy while the K⁺p cross section increases.     

Elastic and inelastic positron-helium scattering

Elastic and inelastic positron--helium scatterings have been investigated with the coupled-channel optical method (CCO). Ionization continuum and positronium formation channels are included via a complex equivalent-local optical potential. Calculations are reported of cross sections of elastic scattering, total excitation and n=2, 3, and 4 excitations of ground-state helium for incident energies from 30~eV to 400~eV. The present calculation shows that the ionization and Ps-formation channels significantly affect the cross sections of elastic and inelastic positron--helium scatterings.     

Diffraction at the LHC – antishadow scattering?

Numerical predictions for the global characteristics of proton–proton interactions are given for the LHC energy. Possibilities for the discovery of the antishadow scattering mode and its physical implications are discussed. Received: 18 August 2000 / Revised version: 9 July 2001 / Published online: 7 September 2001     

Elastic scattering of π−, K− and p̄ from protons at 9.8 and 13.6 GeV/c

Measurements have been made of the differential cross section for π⁻−p elastic scattering at 9.8 GeV/c in the angular range 25°–120° c.m.s. Together with existing data, an almost complete angular distribution has now been obtained at this momentum. Measurements have also been made over more restricted angular ranges for 9.7 GeV/c K⁻−p and −p-p elastic scattering and 13.6 GeV/c π⁻−p and K⁻ −p elastic scattering.     

Antiproton-proton annihilation at rest intoπ + π − η ′ andπ + π − η from atomicS andP states

We have measured the branching ratios for (bar pp) annihilation at rest intoπ ⁺ π ^? η andπ ⁺ π ^? η′ in hydrogen gas in two data samples that have different fractions ofS-wave andP-wave initial states. The branching ratios are derived from a comparison with the topological branching ratio for (bar pp) annihilations into four charged pions of (49±4)% and the branching ratio intoπ ⁺ π ^? π ⁺ π ^? π ⁰ of (18.7±1.6)%. We find a significant reduction of the branching ratios fromP-states for (bar pp to pi ^ + pi ^ - eta ) andπ ⁺ π ^? η′ in comparison toS-state annihilation. $$begin{gathered} BR(S - wave to pi ^ + pi ^ - eta ) = (13.7 pm 1.46) cdot 10^{ - 3} hfill BR(P - wave to pi ^ + pi ^ - eta ) = (3.35 pm 0.84) cdot 10^{ - 3} hfill BR(S - wave to pi ^ + pi ^ - eta ') = (3.46 pm 0.67) cdot 10^{ - 3} hfill BR(P - wave to pi ^ + pi ^ - eta ') = (0.61 pm 0.33) cdot 10^{ - 3} . hfill end{gathered} $$ In a partial wave analysis of theπ ⁺ π ^? η Dalitz plot we find the following contributions: Phase space, (a_2^ + (1320)pi ^ mp ) ,ηρ⁰ andf ₂(1270)η: $$begin{gathered} BR(S - wave to pi ^ + pi ^ - eta PS) = (6.31 pm 1.22) cdot 10^{ - 3} hfill BR(P - wave to pi ^ + pi ^ - eta PS) = (0.47 pm 0.26) cdot 10^{ - 3} hfill BR(^1 S_0 to a_2^ pm (1320)pi ^ mp ) = (2.59 pm 0.73) cdot 10^{ - 3} hfill BR(^3 S_1 to a_2^ pm (1320)pi ^ mp ) = (1.31 pm 0.48) cdot 10^{ - 3} hfill BR(P - wave to a_2^ pm (1320)pi ^ mp ) = (1.31 pm 0.69) cdot 10^{ - 3} hfill BR(^3 S_1 to rho eta ) = (3.29 pm 0.90) cdot 10^{ - 3} hfill BR(^1 P_1 to rho eta ) = (0.94 pm 0.53) cdot 10^{ - 3} hfill BR(^1 S_0 to f_2 (1270)eta ) = (0.083 pm 0.086) cdot 10^{ - 3} hfill BR(P - wave to f_2 (1270)eta ) = (0.64 pm 0.26) cdot 10^{ - 3} . hfill end{gathered} $$ We find a 2 σ effect for the reaction (bar pp to a_0^ pm (980)pi ^ mp ) , (a_0^ pm to eta pi ^ pm ) , with a branching ratio of (0.13±0.07)·10^?3. For η' production we give a branching ratio of (bar pp to rho eta ') of (1.81±0.44)·10^?3 from³ S ₁. We estmate a contribution of about 0.3·10^?3 for ρη' fromP-states. The ratio of ρη and ρη' rpoduction is used to test the validity of the quark line rule. In theπ ⁺ π ^? π ⁺ π ^? γ final state we do not observe the reaction (bar pp to pi ^ + pi ^ - omega ) , ω→π ⁺ π ^? λ and derive an upper limit of 3·10^?3 for decay modeω→π ⁺ π ^? λ.     

π+p elastic scattering at 3.6 GeV/c

The elastic scattering of 3.6 GeV/c π⁺ mesons by protons has been studied in a hydrogen bubble chamber experiment. The elastic cross section has a measured value of 7.07 ± 0.20 mb. The forward diffraction peak has been fitted in the region 0.05 ≦ −t ≦ 0.6 (GeV/c)² by a form (dσ/dt) = Ae^Bt, where A = 46.5 ± 1.8 mb/(GeV/c)² and B = 6.85 ± 0.20 (GeV/c)⁻². From this fit and the optical theorem, the magnitude of the ratio of real to imaginary forward amplitude is 0.39 ± 0.06, in reasonable agreement with dispersion relation calculations and simple Regge model predictions.     

A study ofK + p elastic scattering and reactionK + p→K + pπ+π− at 70 GeV/c

Results are presented onK ⁺ p elastic scattering and on the reactionK ⁺ p→K ⁺ pπ⁺π^? at 70 GeV/c. For the elastic channel, we measured the total ((2.29±0.04)mb) and differentialdσ/dt cross sections. The reactionK ⁺ p→K ⁺ pπ⁺π^? has a total cross section of (470±23) μb and is shown to be dominated by diffractive dissociation processes. The contributions of the quasi-two-body channels $$K^ + p \to K*^0 (890)\Delta ^{ + + } (1,236)$$ and $$K^ + p \to K*^0 (1,430)\Delta ^{ + + } (1,236)$$ and of the Double-Pomeron Exchange (DPE) processes are estimated.     

Measurements of π+p,K+p and pp elastic scattering)

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.Presented by F. A. Yotch at the Symposium on Hadron-Hadron Scattering at High Energies, Liblice, Czechoslovakia, June 16–21, 1975.The authors would like to express their gratitude to A. A.Logunov, Yu. D.Prokoshkin, L. D.Soloviev and V. A.Yarba for their support of this experiment. We are indebted to CERN Administration for giving us a permission to use a part of equipment of the CIBS spectrometer and to W.Kienzle for useful discussions.     

Production of γγ+2 jets from double parton scattering in proton-proton collisions at the LHC

Cross sections for the production of pairs of photons plus two additional jets produced from double parton scattering in high-energy proton-proton collisions at the LHC are calculated for the first time.The estimates are based on the theoretical perturbative QCD predictions for the productions of γγ at next-to-next-to-leading-order,jet+jet and γ+jet at next-to-leading-order,for their corresponding single-scattering cross sections.The cross sections and expected event rates for γγ+2 jets from double parton scattering,after typical acceptance and selections,are given for proton-proton collisions with the collision energy s~(1/2)=13 TeV and integrated luminosity of 100 fb~(-1) planned for the following years,and also s~(1/2)=14 TeV with 3000 fb~(-1) of integrated luminosity as the LHC design.     

D* meson production cross sections in e − p and e + p scattering processes at the HERA collider

The cause of the D* meson production cross sections in e ^? p and e ⁺ p deep inelastic scattering processes in the ZEUS experiment at the HERA collider that are anomalously different is determined.     

Kp and πp backward elastic scattering at 5.2 and 6.9 GeV/c

The angular distributions of K⁺p and π⁺p backward elastic scattering have been measured at 5.2 and 6.9 GeV/c. Backward π^-p and K^-p elastic scattering were studied at 6.9 GeV/c. Backward peaks are observed in K⁺p scattering with an energy dependence of the form s⁻⁴.     

High Energy Elastic p and p p Differential Cross Sections

<正>(Updated September 2013.COMPAS group.IHEP,Protvino)Using new results from FNAL-COLLIDER-D0 experiment in pp elastic collisions at s~(1/2)=1.96 TeV[1],CERN-LHC-TOTEM experiment in p p elastic collisions at s~(1/2)=7,8 TeV[2-3]and PAO experiment in proton-air collisions at 57 TeV[4]the amplitudes of the elastic p p and p p collisions are investigated in a most broad region in s~(1/2)and t via three observables da/dt(s,t).σ~(tot)(s),and p(s).The summary of the database for dσ/dt(s,t)is presented in Figure 50.10.where projection of the dσ/dt(s~(1/2),t)to the(da/dt,—t)plane orthogonal to the s~(1/2)axis is displayed.