NN¯annihilation at the open charm threshold

Abstract

We discuss the pp annihilation into a pair of charmed D mesons not far from the threshold of the reaction. An interesting interference pattern in the differential cross section is predicted to arise from the existence of both t-channel charmed-baryon exchange and s-channel qii charmonium resonance amplitudes. We argue that the experimental study of this process would provide new and valuable information about the unknown ppP" and A , N D couplings. These are important to know to solve the long-standing puzzle of the heavy flavor content of baryons and to test the semilocal duality. PACS number(s): 13.85.Ni, 14.20.Lq, 14.40.LbThere exist many meson states which couple to the NN system. These states then appear as the poles in the amplitudes of the NN interaction and this, in principle, can lead to observable effects. However, the common situation in the light quark sector is that the widths of the resonances are large; they therefore overlap and interfere. The necessity to account, in addition, for a n interference with the (generally unknown) t-channel exchange amplitudes further complicates the situation, making a clean and detailed analysis an extremely difficult task.In this sense a rather uncommon situation is encountered in the pp annihilation into a pair of D mesons close to the threshold. The s-channel resonance here is the k1'(3770) charmonium state with a relatively small width of I? ~2 3 . 6 MeV. The nearest charmonia are too far and narrow to cause any appreciable interference effects, so the pole corresponding to 9" can, to a good accuracy, be considered as isolated. In addition, there exist of course nonresonant t-channel amplitudes, corresponding to the exchange of the states with the quantum numbers of charmed baryon(s). The relation between the strengths of the resonant and nonresonant amplitudes depends on two couplings, N N~I I and N,ND. Almost nothing is known at present about the values of the corresponding coupling constants, apart from a few rather controversial predictions 11-51. A possible admixture of the light-quark-antiquark pairs in the wave function of the 9'' can further complicate the situation, giving rise to a nonperturbative contribution to the pp + k" amplitude. Another interesting issue concerning the N,ND coupling is that the knowledge of its value is desirable to solve the problem of the intrinsic heavy flavor content of the baryons [6,7]. The arguments listed above indicate that the study of the pp + DD reaction is interesting, but at the same time leave seemingly little chance to 'On leave of absence from Moscow State University, Moscow, Russia. make a reliable prediction for the relative importance of s-and t-channel exchange amplitudes.There exists, however, an attractive theoretical scheme which, when applied to our situation, gives a definite answer-the (semilocal) duality 18-1 11. Namely, the senlilocal duality implies that the averages (over a finiteenergy segment) of cross sections corresponding to the sum of all possible amplitudes in s and t channels, respectively,...

ψ(3770)resonance and its production inp¯p→DHaidenbauer1, Krein2 2015Phys. Rev. D101152View full textAdd to dashboardCite

“…The cross section was found to be in the order of 10 -100 nb and it turned out to be comparable to those predicted by other model calculations in the literature [2][3][4][5][6][7].…”

Production of charmed pseudoscalar mesons in antiproton-proton annihilation

“…This allows us to shed light on the model dependence of our results. Furthermore, we compare our predictions with the ones of other model calculations of thē pp → DD reaction from the literature [29][30][31][32][33][34]. In some of those studies a quark-gluon description based on a factorization hypothesis of hard and soft processes [29,34] is employed, while in others a non-perturbative quark-gluon string model is used, based on secondary Regge pole exchanges including absorptive corrections [30,32,33].…”

Charmed meson rescattering in the reaction $$ \bar pd \uparrow \bar DDN $$

“…Unfortunately, so far there is no experimental information about this reaction and even theoretical studies are rather scarce [54,55,56]. In Ref.…”