论文标题
Pion质量差的晶格计算$ M_ {π^{+}} -M_ {π^{0}} $ at Order $ \ Mathcal {O}（α__{em}）$
Lattice calculation of the pion mass difference $M_{π^{+}}-M_{π^{0}}$ at order $\mathcal{O}(α_{em})$
论文作者
论文摘要
我们提出了一个晶格计算的晶格计算$ m_ {π^{+}} - m_ {π^{0}} $，按顺序$ \ nathcal {o}（α__{em} $）使用扩展的twist twist质量协作制作$ n quark $ n _ = 2+n_ _ {在晶格间距（$ a \ simeq 0.062，0.082，0.089〜 {\ rm fm} $）和pion质量范围内$m_π\ simeq 250-500〜 {\ rm mev} $。我们采用RM123方法，并在电磁耦合$α_{em} $中以领先顺序扩展Isospin对称点周围的路径综合点。利用最近提出的RTM方案，我们评估了整个$ \ Mathcal {o}（α__{em}）$贡献，并包含断开的图表。在物理点上，在执行连续和无限的音量外推后，我们获得了$ m_ {π^{+}}} -M_ {π^{0}} = 4.622〜（95）〜{\ rm mev} $，这是与实验结果$ [m_ _ {m _ {m _}} - m_ {π^{0}}]^{exp。} = 4.5936（5）〜{\ rm mev} $。
We present a lattice calculation of the charged/neutral pion mass difference $M_{π^{+}}-M_{π^{0}}$ at order $\mathcal{O}(α_{em})$ using the gauge configurations produced by the Extended Twisted Mass Collaboration with $N_{f}=2+1+1$ dynamical quark flavours at three values of the lattice spacing ($a \simeq 0.062, 0.082, 0.089~{\rm fm}$) and pion masses in the range $M_π \simeq 250-500~{\rm MeV}$. We employ the RM123 method and expand the path-integral around the isospin symmetric point at leading order in the electromagnetic coupling $α_{em}$. Making use of the recently proposed RTM scheme, we evaluate the full $\mathcal{O}(α_{em})$ contribution, with the inclusion of the disconnected diagram. At the physical point, after performing the continuum and infinite volume extrapolation, we obtain the value $M_{π^{+}}-M_{π^{0}}= 4.622~(95)~{\rm MeV}$ which is in good agreement with the experimental result $[ M_{π^{+}} - M_{π^{0}} ]^{exp.} = 4.5936(5)~{\rm MeV}$.
