论文标题
关于$ T_ {4C}（6900）$ TETRAQUARK生产的机制
On the mechanism of $T_{4c}(6900)$ tetraquark production
论文作者
论文摘要
我们讨论了一种新状态的生产机制，即一种推定的完全魅力四夸克，LHCB最近在$ J/ψJ/ψ$通道中观察到M = 6.9 GEV。都考虑了单个Parton散射（SP）和双Parton散射（DPS）机制。我们计算了四夸克系统的不变质量分布，用于SPS的SPS和DPS生产$ c c \ bar c \ bar c \ bar c $在$ k_t $ - factorization方法中，具有现代未集成的Gluon分布功能（UGDFS）。 DPS的所谓贡献几乎比SPS大两个数量级，但目前未知Tetraquark形成机理。在共振位置周围施加一个质量窗口，我们计算出$ p_ {t，4c} $的相应分布 - 潜在的四夸克横向动量。此外还计算出$ j/ψj/ψ$连续体的横截面，包括SPS（框图）和大小相似的DPS贡献。估计形成概率试图重现LHCB信噪比的比率。假设不同的旋转方案（$ 0^+$和$ 0^ - $），在$ k_t $ -Factorization方法中执行SPS $ g g \ to t_ {4c}（6900）$融合机制的计算。 $ 0^+$分配优于$ 0^ - $一个，通过将信号和背景的横向动量分布与LHCB初步数据进行比较，假设SPS机制优势。目前，DPS形成机理没有可靠的方法，因为这是一个复杂的多体问题。
We discuss the production mechanism of a new state, a putative fully charm tetraquark, observed recently by the LHCb at M = 6.9 GeV in the $J/ψJ/ψ$ channel. Both single parton scattering (SPS) and double parton scattering (DPS) mechanisms are considered. We calculate the distribution in the invariant mass of the four-quark system $M_{4c}$ for SPS and DPS production of $c c \bar c \bar c$ in the $k_t$-factorization approach with modern unintegrated gluon distribution functions (UGDFs). The so-calculated contribution of DPS is almost two orders of magnitude larger than the SPS one, but the tetraquark formation mechanism is unknown at present. Imposing a mass window around the resonance position we calculate the corresponding distribution in $p_{t,4c}$ -- the potential tetraquark transverse momentum. The cross section for the $J/ψJ/ψ$ continuum is calculated in addition, again including SPS (box diagrams) and DPS contributions which are of similar size. The formation probability is estimated trying to reproduce the LHCb signal-to-background ratio. The calculation of the SPS $g g \to T_{4c}(6900)$ fusion mechanism is performed in the $k_T$-factorization approach assuming different spin scenarios ($0^+$ and $0^-$). The $0^+$ assignment is preferred over the $0^-$ one by the comparison of the transverse momentum distribution of signal and background with the LHCb preliminary data assuming the SPS mechanism dominance. There is no reliable approach for the DPS formation mechanism of tetraquarks at present as this is a complicated multi-body problem.
