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arXiv 1602.08100hep-phhep-ex
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750 GeV $\sim$对撞机上双光子过剩的重费米子束缚态和宇宙学约束$\sim$

Heavy Fermion Bound States for Diphoton Excess at 750GeV $\sim$ Collider and Cosmological Constraints $\sim$

Chengcheng Han, Koji Ichikawa, Shigeki Matsumoto, Mihoko M. Nojiri, Michihisa Takeuchi

摘要:

在大型强子对撞机(LHC)上产生的具有足够小宽度的有色重粒子可以形成非相对论束缚态,并湮灭为双光子末态。双光子的不变质量大约是有色粒子质量的两倍。本文研究了这种束缚态是否能解释ATLAS和CMS报道的750 GeV双光子过剩。我们发现SU(2)$_L$单重态色费米子$X$与$Y_X=4/3$的最佳拟合信号截面。有了这样一个奇异的超荷,粒子预计将通过一些更高维的运营商衰变,符合小宽度假设。如果$X$和$χ$在某些守恒的$Z_2$对称性下都是奇数,则$X$的衰变可能涉及稳定粒子$χ$。在这种情况下,粒子$X$受到喷流+丢失的$E_T$搜索ATLAS和CMS在8 TeV和13 TeV的约束。我们发现,如果$X$和$χ$之间的质量差大于$\sim$ 30 GeV(对于$m_X \sim 375$ GeV),这种情况仍然存在。即使假设$χ$的对湮灭很小,如果$X$和$χ$之间的质量差小于$\sim$ 40 GeV,则$χ$的残余密度足够小。

英文摘要:

A colored heavy particle with sufficiently small width may form non-relativistic bound states when they are produced at the large hadron collider\,(LHC), and they can annihilate into a diphoton final state. The invariant mass of the diphoton would be around twice of the colored particle mass. In this paper, we study if such bound state can be responsible for the 750 GeV diphoton excess reported by ATLAS and CMS. We found that the best-fit signal cross section is obtained for the SU(2)$_L$ singlet colored fermion $X$ with $Y_X=4/3$. Having such an exotic hypercharge, the particle is expected to decay through some higher dimensional operators, consistent with the small width assumption. The decay of $X$ may involve a stable particle $χ$, if both $X$ and $χ$ are odd under some conserved $Z_2$ symmetry. In that case, the particle $X$ suffers from the constraints of jets + missing $E_T$ searches by ATLAS and CMS at 8 TeV and 13 TeV. We found that such a scenario still survives if the mass difference between $X$ and $χ$ is above $\sim$ 30 GeV for $m_X \sim 375$ GeV. Even assuming pair annihilation of $χ$ is small, the relic density of $χ$ is small enough if the mass difference between $X$ and $χ$ is smaller than $\sim$ 40 GeV.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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