750 GeV标量共振：单态解与双光子过量的探究

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本文主要探讨了单重态标量共振与最近ATLAS和CMS在13 TeV质子-质子碰撞实验中观察到的约750 GeV双光子（diphoton）过量现象之间的关系。《物理快报B》的一篇论文分析了这一新发现，并指出单重态标量共振模型作为一种可能的解释，能够在很大程度上解释这个异常信号，同时又不违反现有的理论约束。作者Samuel D. McDermott、Patrick Meade和Harikrishnan Ramani C. N. Yang来自美国斯托尼 Brook的理论物理研究所，他们对这一模型进行了深入探讨。他们注意到，尽管单重态标量共振本身作为解释750 GeV信号的一个候选，其大总宽度可能需要超越仅仅通过环路级（loop-level）衰变来解释。这暗示着可能存在其他物理机制或者额外的粒子贡献，这将为模型带来新的边界和信号特征。文章还强调了实验结果中750 GeV共振的特征对于模型的重要性，特别是当它涉及到大总宽度时。如果这一特征得到进一步证实，它可能会对标准模型之外的新物理领域提供线索，比如潜在的超对称性粒子或额外维度效应。此外，文中提到了研究过程中伴随的稳健Zγ（Z玻色子与光子的混合）信号，这是一个独特的模型预言，可能在未来的实验中被检测到，从而进一步验证或排除这种理论。这篇论文不仅关注了单重态标量共振模型如何解释双光子过量，还讨论了其与实验数据的兼容性，以及可能带来的理论挑战和未来研究方向。这对于理解当前高能物理学领域的热点问题——750 GeV异常，具有重要的学术价值。

Physics Letters B 755 (2016) 353–357

Contents lists available at ScienceDirect

Physics Letters B

www.elsevier.com/locate/physletb

Singlet scalar resonances and the diphoton excess

Samuel D. McDermott

∗

, Patrick Meade, Harikrishnan Ramani

C. N. Yang Institute for Theoretical Physics, Stony Brook, NY 11794, United States

a r t i c l e i n f o a b s t r a c t

Article history:

Received

17 December 2015

Received

in revised form 4 February 2016

Accepted

15 February 2016

Available

online 23 February 2016

Editor:

A. Ringwald

ATLAS and CMS recently released the ﬁrst results of searches for diphoton resonances in 13 TeV data,

revealing a modest excess at an invariant mass of approximately 750 GeV. We ﬁnd that it is generically

possible that a singlet scalar resonance is the origin of the excess while avoiding all other constraints.

We highlight some of the implications of this model and how compatible it is with certain features of

the experimental results. In particular, we ﬁnd that the very large total width of the excess is diﬃcult to

explain with loop-level decays alone, pointing to other interesting bounds and signals if this feature of

the data persists. Finally we comment on the robust Zγ signature that will always accompany the model

we investigate.

(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP

1. Introduction

The excess found in diphoton ﬁnal states in the 13 TeV ATLAS

and CMS data at 750 GeV [1,2] presents an interesting model-

building

challenge. (While this paper was in preparation a number

of attempts at explaining the diphoton excess appeared [3].) ATLAS

and CMS both characterize the events that make up their signal to

have the same composition as the background in sidebands [1,2].

Therefore, we assume that this peak in the event spectrum comes

from the direct production of a resonance rather than a cascade

decay.

the signal is caused by a resonance that decays to diphotons,

the Landau–Yang theorem [4] restricts the spin of the resonance

to 0 or 2. The spin 2 possibility was preliminarily investigated by

CMS [2], and, though interesting, it is diﬃcult to construct a model

that satisﬁes all constraints. However, an example of a scalar res-

onance

which decays to diphotons is already provided by the SM

Higgs, illustrating that it is straightforward to construct a “cousin”

of the Higgs to explain this excess.

Models

of a scalar resonance which explain the excess can

come from sectors with a wide variety of ﬁeld content and quan-

tum

number assignments [3]. The simplest possibility which avoids

many correlated bounds is a resonance that is a singlet under the

Standard Model gauge group. This implies that the coupling to

protons and photons is generated by loops of new non-Standard

Model particles that are colored and charged.

Corresponding author.

E-mail

address: samuel.mcdermott@stonybrook.edu (S.D. McDermott).

As discussed in more detail below, the width of the excess

preferred by ATLAS and CMS [1,2] immediately implies additional

constraints on singlet models. The preferred ﬁt from ATLAS has a

width of 45 GeV [1] with a local signiﬁcance of 3.9σ , although

this represents only a marginal improvement over a narrow-width

model. CMS slightly prefers a narrow width [2], but overall has

a smaller number of events, which can be partially attributed to

their lower luminosity. The model point favored by CMS data has

a width of O(100 MeV), with an excess of 2.6σ . However, CMS

is compatible at a similar level of conﬁdence with a width of

42 GeV. It should be noted that ATLAS, while compatible with

narrow width, prefers a larger width for several reasons. In the

narrow width model, ATLAS ﬁnds a pull based on marginalizing

over the width. This indicates a resonance width larger than the

experimental resolution of 5.3GeV(we estimate this by a linear

interpolation on the diphoton invariant mass resolution parameter

listed in section 5 of [1]). Additionally, when comparing the excess

between 13 TeV and 8TeV, ATLAS ﬁnds that the narrow width

is only compatible at the 2.2σ level whereas the larger width is

compatible with a smaller 1.4σ tension. Given the limited data it

is therefore still possible to have a narrow width (indicative, as we

discuss below, of strictly loop-induced processes), but it is more

experimentally favored to have a larger width.

This

brings singlet models under some tension. The number of

observed photons is given by

γγ

= σ

prod



γγ



tot

×L ×  × A, (1)

http://dx.doi.org/10.1016/j.physletb.2016.02.033

0370-2693/

SCOAP

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