arXiv subjects

G. B. Pontecorvo

Publications and source records attributed to G. B. Pontecorvo.

5 recordsLinked to original sources

arXiv2006

Resonant behaviour in double charge exchange reaction of π^+ mesons on the nuclear photoemulsion

The invariant mass spectra of the $ppπ^-$ and $pp$ systems produced in the double charge exchange (DCX) of positively charged pions on photoemulsion are analysed. A pronounced peak is observed in the $ppπ^-$ invariant mass spectrum, while the $M_{pp}$ spectrum exhibits a strong Migdal-Watson effect of the proton-proton final state interaction. These findings are in favor of the $NN$-decoupled $NNπ$ pseudoscalar resonance with T=0 called $d'$.

hep-ph↗

arXiv2000

$ϕ$ and $ω$ Meson Production in pp Reactions at $p_{lab}$=3.67 GeV/c

The exclusive production cross sections for $ω$ and $ϕ$ mesons have been measured in proton-proton reactions at $p_{lab}=3.67$ GeV/c. The observed $ϕ/ω$ cross section ratio is $(3.8\pm0.2^{+1.2}_{-0.9})\times 10^{-3}$. After phase space corrections, this ratio is enhanced by about an order of magnitude relative to naive predictions based upon the Okubo-Zweig-Iizuka (OZI) rule, in comparison to an enhancement by a factor $\sim 3$ previously observed at higher beam momenta. The modest increase of this enhancement near the production threshold is compared to the much larger increase of the $ϕ/ω$ ratio observed in specific channels of $\bar pp$ annihilation experiments. Furthermore, differential cross section results are also presented which indicate that although the $ϕ$ meson is predominantly produced from a $^3P_1$ proton-proton entrance channel, other partial waves contribute significantly to the production mechanism at this beam momentum.

nucl-ex↗

arXiv2000

Production of $η\prime$ Mesons in the $pp \to ppη\prime$ Reaction at 3.67 GeV/c

The ratio of the total exclusive production cross sections for $η\prime$ and $η$ mesons has been measured in the $pp$ reaction at $p_{beam}=3.67$ GeV/c. The observed $η\prime/η$ ratio is $(0.83\pm{0.11}^{+0.23}_{-0.18})\times 10^{-2}$ from which the exclusive $η\prime$ meson production cross section is determined to be $(1.12\pm{0.15}^{+0.42}_{-0.31})μb$. Differential cross section distributions have been measured. Their shape is consistent with isotropic $η\prime$ meson production.

nucl-ex↗

arXiv1999

K$^-$ Meson Production in the Proton-Proton Reaction at 3.67 GeV/c

The total cross section of the reaction $pp\to ppK^+K^-$ has been determined for proton--proton reactions with $p_{beam}=3.67 GeV/c$. This represents the first cross section measurement of the $pp \to ppK^-K^+$ channel near threshold, and is equivalent to the inclusive $pp\to ppK^-X$ cross section at this beam momentum. The cross section determined at this beam momentum is about a factor 20 lower than that for inclusive $pp\to ppK^+X$ meson production at the same CM energy above the corresponding threshold. This large difference in the $K^+$ and $K^-$ meson inclusive production cross sections in proton-proton reactions is in strong contrast to cross sections measured in sub-threshold heavy ion collisions, which are similar in magnitude at the same energy per nucleon below the respective thresholds.

nucl-ex↗

arXiv1999

Spin Transfer in Exclusive Lambda Production from pp Collisions at 3.67 GeV/c

We report the first polarization transfer measurements for exclusive hyperon production reactions. The normal spin transfer coefficient DNN for pp -> p K+ Lambda is large and negative for forward Lambda production at a beam momentum of 3.67 GeV/c, a result qualitatively consistent with expectations for a mechanism dominated by kaon-exchange and rescattering. The sign of DNN is opposite to that observed in the fragmentation regime for inclusive Lambda production at much higher energies.

nucl-ex↗