Search

The photoproduction of P-wave doubly charmed baryon (Ξcc) is investigated in the context of future high-energy and high-luminosity e+e− colliders. The direct photoproduction via the sub-process γ + γ → Ξ cc + c ¯ + c ¯ and the resolved channel γ + g → Ξ cc + c ¯ + c ¯ are considered. Within the framework of non-relativistic QCD, the calculation encompasses four P-wave (cc)-diquark configurations: cc 3 ¯ [1P1], (cc)6[3P0], (cc)6[3P1] and (cc)6[3P2]. The two S-wave states, cc 3 ¯ [3S1] and (cc)6[1S0], are also included for comparison. The cross sections, as well as the differential distributions involving transverse momentum, rapidity, and angular variables, have been computed. Numerical results reveal that the resolved photoproduction process plays a significant role and can provide dominant contributions. The photoproduction rate of the P-wave Ξcc is approximately one order of magnitude lower than that of the S-wave. [ABSTRACT FROM AUTHOR]

Based on the non-relativistic quantum chromodynamics factorization framework, we study the inclusive J/ψ photoproduction at the future high energy e+e− collider, International Linear Collider(ILC), where the initial photons come from the back-scattering of laser and electron (positron). The intermediate states, c c ¯ (3 S 1 1 ,1 S 0 8 ,3 S 1 8 , 3 P 0 , 1 , 2 8 ), and resolved photoproduction processes are considered. Numerical results show that the cross section of J/ψ photoproduction at the ILC could be very large, and the single resolved pro- cess via c c ¯ (3 S 0 8 ) intermediate state dominates primarily the production. We also present various kinematic distributions for J/ψ photoproduction. Combining the high luminosity of the collision, J/ψ photoproduction at the ILC shall provide a good platform to test the NRQCD factorization. [ABSTRACT FROM AUTHOR]

In the paper, we calculate the fragmentation functions for g → Bc and g → B c ∗ . The ultraviolet divergences in the calculation are removed through the renormalization of the operator definition of the fragmentation functions under the modified minimal subtrac- tion scheme. We then obtain the fragmentation functions D g → B c (z, μF) and D g → B c ∗ (z, μF), which are presented as figures and fitting functions. The obtained fragmentation functions are complementary to the previous work on the next-to-leading order fragmentation functions for b ¯ → Bc( B c ∗ ) and c → Bc( B c ∗ ). [ABSTRACT FROM AUTHOR]

In this paper, we make a detailed study on the production of the B c , B c ∗ , B c (2 1 S 0) , and B c ∗ (2 3 S 1) mesons via the three planned running modes (Z, W, and H) at the future Circular Electron–Positron Collider (CEPC). The fragmentation-function and full nonrelativistic QCD approaches are adopted to calculate the production cross sections. Considering the excited states shall decay to the ground B c state (e.g. 1 1 S 0 -state) with almost 100 % probability, our numerical results show that up to next-to-leading order QCD corrections, there are about 1.4 × 10 8 B c events to be accumulated via the Z mode ( s = m Z ) of the CEPC, but only about 1.6 × 10 4 and 1.1 × 10 4 B c events to be accumulated via the W ( s = 160 GeV ) and H ( s = 240 GeV ) modes, respectively. Since the Z mode is the best mode among the three planned modes of the CEPC for studying the production of the B c , B c ∗ , B c (2 1 S 0) , and B c ∗ (2 3 S 1) mesons and the differential distributions of these mesons may be measured precisely at this mode, we further present the differential cross sections d σ / (d z d cos θ) and d σ / d z via the Z mode of the CEPC. [ABSTRACT FROM AUTHOR]

In the paper, we calculate the fragmentation functions for c → ηc and b → ηb up to next-to-leading-order (NLO) QCD accuracy. The ultraviolet divergences in the real corrections are removed through operator renormalization under the modified min- imal subtraction scheme. We then obtain the fragmentation functions D c → η c (z, μF) and D b → η b (z, μF) up to NLO QCD accuracy, which are presented as figures and fitting functions. The numerical results show that the NLO corrections are significant. The sensitives of the fragmentation functions to the renormalization scale and the factorization scale are analyzed explicitly. [ABSTRACT FROM AUTHOR]

In this paper, we present a new analysis on the P-wave charmonium annihilation into two photons up to next-to-next-to-leading order (NNLO) QCD corrections by using the principle of maximum conformality (PMC). The conventional perturbative QCD prediction shows strong scale dependence and deviates largely from the BESIII measurements. After applying the PMC, we obtain a more precise scale-invariant pQCD prediction, which also agrees with the BESIII measurements within errors, i.e. R = Γ γ γ (χ c 2) / Γ γ γ (χ c 0) = 0.246 ± 0.013 , where the error is for Δ α s (M τ) = ± 0.016 . By further considering the color-octet contributions, even the central value can be in agreement with the data. This shows the importance of a correct scale-setting approach. We also give a prediction for the ratio involving χ b 0 , b 2 → γ γ , which could be tested in future Belle II experiment. [ABSTRACT FROM AUTHOR]