CMS-PAS-HIG-21-016

CMS-PAS-HIG-21-016
Search for exotic Higgs boson decays H $\rightarrow \mathcal{A}\mathcal{A} \rightarrow 4\gamma$ with events containing two merged photons in proton-proton collisions at $\sqrt{s} =$ 13 TeV
CMS Collaboration
March 2022

Abstract: The result of a direct search for the exotic Higgs boson decay $\mathrm{H}\rightarrow\mathcal{A}\mathcal{A}$ , $\mathcal{A}\rightarrow\gamma\gamma$ is presented, using events with a final state containing two photons. The hypothetical particle $\mathcal{A}$ is a low-mass, boosted scalar decaying promptly to two highly merged photons, misreconstructed as a single photon-like object. The data were collected by the CMS experiment at the CERN LHC from proton-proton collisions at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 136 fb $^{-1}$ . No excess of events above the estimated background is found. Upper limits on the branching fraction $\mathcal{B}(\mathrm{H} \rightarrow \mathcal{A}\mathcal{A} \rightarrow 4\gamma)$ of 0.9--3.3 $\times$ 10 $^{-3}$ are set at the 95% confidence level for masses of $\mathcal{A}$ in the range 0.1 $< m_{\mathcal{A}} <$ 1.2 GeV.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRL 131 (2023) 101801. The superseded preliminary plots can be found here.

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Simulated $m_{\Gamma,1}$ vs. $m_{\Gamma,2}$ 2D distributions for $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events passing the selection criteria for masses $m_{{\mathcal {A}}}=$ 0.1 (left), 0.4 (center), and 1 GeV (right). The distributions are normalized to the total integrated luminosity in the studied data set, assuming a total signal cross section times branching fraction of 1 pb. The color scales to the right of each plot give the number of events per bin.
png pdf	Figure 1-a: Simulated $m_{\Gamma,1}$ vs. $m_{\Gamma,2}$ 2D distributions for $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events passing the selection criteria for masses $m_{{\mathcal {A}}}=$ 0.1 (left), 0.4 (center), and 1 GeV (right). The distributions are normalized to the total integrated luminosity in the studied data set, assuming a total signal cross section times branching fraction of 1 pb. The color scales to the right of each plot give the number of events per bin.
png pdf	Figure 1-b: Simulated $m_{\Gamma,1}$ vs. $m_{\Gamma,2}$ 2D distributions for $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events passing the selection criteria for masses $m_{{\mathcal {A}}}=$ 0.1 (left), 0.4 (center), and 1 GeV (right). The distributions are normalized to the total integrated luminosity in the studied data set, assuming a total signal cross section times branching fraction of 1 pb. The color scales to the right of each plot give the number of events per bin.
png pdf	Figure 1-c: Simulated $m_{\Gamma,1}$ vs. $m_{\Gamma,2}$ 2D distributions for $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events passing the selection criteria for masses $m_{{\mathcal {A}}}=$ 0.1 (left), 0.4 (center), and 1 GeV (right). The distributions are normalized to the total integrated luminosity in the studied data set, assuming a total signal cross section times branching fraction of 1 pb. The color scales to the right of each plot give the number of events per bin.
png pdf	Figure 2: Observed mass distributions from signal candidate events. Center: the observed $m_{\Gamma,1}$ vs. $m_{\Gamma,2}$ 2D plot for candidate events in the $m_{\mathrm{H}}$ -SR region. The color scale on the right of the plot gives the number of events per bin. The contours of simulated $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events for $m_{{\mathcal {A}}} =$ 0.4 GeV are plotted at 75% (dashed contour) and $50%$ (dotted contour) of their maximum. The corresponding $m_{\Gamma,1}$ and $m_{\Gamma,2}$ projections for the overlap of the $m_{\mathrm{H}}$ -SR and $m_{{\mathcal {A}}}$ -SR regions are shown in the left and right figures, respectively. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The spectra of simulated $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events for $m_{{\mathcal {A}}}=$ 0.1 (yellow dashed curve), 0.4 (gray dotted curve), and 1.0 GeV (red dash-dotted curve) normalized to their respective expected upper limits times 10 $^3$ are also provided. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure 2-a: Observed mass distributions from signal candidate events. Center: the observed $m_{\Gamma,1}$ vs. $m_{\Gamma,2}$ 2D plot for candidate events in the $m_{\mathrm{H}}$ -SR region. The color scale on the right of the plot gives the number of events per bin. The contours of simulated $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events for $m_{{\mathcal {A}}} =$ 0.4 GeV are plotted at 75% (dashed contour) and $50%$ (dotted contour) of their maximum. The corresponding $m_{\Gamma,1}$ and $m_{\Gamma,2}$ projections for the overlap of the $m_{\mathrm{H}}$ -SR and $m_{{\mathcal {A}}}$ -SR regions are shown in the left and right figures, respectively. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The spectra of simulated $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events for $m_{{\mathcal {A}}}=$ 0.1 (yellow dashed curve), 0.4 (gray dotted curve), and 1.0 GeV (red dash-dotted curve) normalized to their respective expected upper limits times 10 $^3$ are also provided. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure 2-b: Observed mass distributions from signal candidate events. Center: the observed $m_{\Gamma,1}$ vs. $m_{\Gamma,2}$ 2D plot for candidate events in the $m_{\mathrm{H}}$ -SR region. The color scale on the right of the plot gives the number of events per bin. The contours of simulated $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events for $m_{{\mathcal {A}}} =$ 0.4 GeV are plotted at 75% (dashed contour) and $50%$ (dotted contour) of their maximum. The corresponding $m_{\Gamma,1}$ and $m_{\Gamma,2}$ projections for the overlap of the $m_{\mathrm{H}}$ -SR and $m_{{\mathcal {A}}}$ -SR regions are shown in the left and right figures, respectively. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The spectra of simulated $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events for $m_{{\mathcal {A}}}=$ 0.1 (yellow dashed curve), 0.4 (gray dotted curve), and 1.0 GeV (red dash-dotted curve) normalized to their respective expected upper limits times 10 $^3$ are also provided. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure 2-c: Observed mass distributions from signal candidate events. Center: the observed $m_{\Gamma,1}$ vs. $m_{\Gamma,2}$ 2D plot for candidate events in the $m_{\mathrm{H}}$ -SR region. The color scale on the right of the plot gives the number of events per bin. The contours of simulated $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events for $m_{{\mathcal {A}}} =$ 0.4 GeV are plotted at 75% (dashed contour) and $50%$ (dotted contour) of their maximum. The corresponding $m_{\Gamma,1}$ and $m_{\Gamma,2}$ projections for the overlap of the $m_{\mathrm{H}}$ -SR and $m_{{\mathcal {A}}}$ -SR regions are shown in the left and right figures, respectively. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The spectra of simulated $\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma$ events for $m_{{\mathcal {A}}}=$ 0.1 (yellow dashed curve), 0.4 (gray dotted curve), and 1.0 GeV (red dash-dotted curve) normalized to their respective expected upper limits times 10 $^3$ are also provided. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure 3: Observed (black solid curve with points) and median expected (blue dashed curve) 95% CL upper limits on $\mathcal {B}(\mathrm{H} \rightarrow {\mathcal {A}} {\mathcal {A}} \rightarrow 4\gamma)$ as a function of $m_{{\mathcal {A}}}$ . The 68 and 95% CIs around the expected limits are shown by the green and yellow bands, respectively. The upper limit from a previous CMS measurement [1] of $\mathcal {B}(\mathrm{H} \rightarrow \gamma \gamma)$ is shown in red, where the width of the red band represents the uncertainty in the measurement. It is accurate for $m_{{\mathcal {A}}}\approx 0.1 GeV$ where the acceptance is comparable to that for the CMS SM $\mathrm{H} \rightarrow \gamma \gamma$ selection criteria and increases approximately twofold toward $m_{{\mathcal {A}}} =$ 1.0 GeV as the relative acceptance diverges.
png pdf	Figure A1: Observed 2D- $m_{\Gamma}$ distribution from candidate events in the orthogonal, signal-depleted data sample in the $m_{\mathrm{H}}$ -SR. The color scale on the right of the plot gives the number of events per bin.
png pdf	Figure A2: Observed vs. predicted $m_{\Gamma,1}$ (left) and $m_{\Gamma,2}$ (right) distributions in the $m_{{\mathcal {A}}}$ -SB (upper) and $m_{{\mathcal {A}}}$ -SR (lower) from candidate events in the orthogonal, signal-depleted data sample (inv. sel.) in the $m_{\mathrm{H}}$ -SR. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure A2-a: Observed vs. predicted $m_{\Gamma,1}$ (left) and $m_{\Gamma,2}$ (right) distributions in the $m_{{\mathcal {A}}}$ -SB (upper) and $m_{{\mathcal {A}}}$ -SR (lower) from candidate events in the orthogonal, signal-depleted data sample (inv. sel.) in the $m_{\mathrm{H}}$ -SR. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure A2-b: Observed vs. predicted $m_{\Gamma,1}$ (left) and $m_{\Gamma,2}$ (right) distributions in the $m_{{\mathcal {A}}}$ -SB (upper) and $m_{{\mathcal {A}}}$ -SR (lower) from candidate events in the orthogonal, signal-depleted data sample (inv. sel.) in the $m_{\mathrm{H}}$ -SR. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure A2-c: Observed vs. predicted $m_{\Gamma,1}$ (left) and $m_{\Gamma,2}$ (right) distributions in the $m_{{\mathcal {A}}}$ -SB (upper) and $m_{{\mathcal {A}}}$ -SR (lower) from candidate events in the orthogonal, signal-depleted data sample (inv. sel.) in the $m_{\mathrm{H}}$ -SR. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure A2-d: Observed vs. predicted $m_{\Gamma,1}$ (left) and $m_{\Gamma,2}$ (right) distributions in the $m_{{\mathcal {A}}}$ -SB (upper) and $m_{{\mathcal {A}}}$ -SR (lower) from candidate events in the orthogonal, signal-depleted data sample (inv. sel.) in the $m_{\mathrm{H}}$ -SR. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure A3: Predicted 2D- $m_{\Gamma}$ distribution for signal candidate events in the $m_{\mathrm{H}}$ -SR. The color scale on the right of the plot gives the number of events per bin.
png pdf	Figure A4: Observed vs. predicted $m_{\Gamma,1}$ (left) and $m_{\Gamma,2}$ (right) distributions in the $m_{{\mathcal {A}}}$ -SB from signal candidates events in the $m_{\mathrm{H}}$ -SR. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure A4-a: Observed vs. predicted $m_{\Gamma,1}$ (left) and $m_{\Gamma,2}$ (right) distributions in the $m_{{\mathcal {A}}}$ -SB from signal candidates events in the $m_{\mathrm{H}}$ -SR. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.
png pdf	Figure A4-b: Observed vs. predicted $m_{\Gamma,1}$ (left) and $m_{\Gamma,2}$ (right) distributions in the $m_{{\mathcal {A}}}$ -SB from signal candidates events in the $m_{\mathrm{H}}$ -SR. The observed distributions are given by the black points and the predicted background distributions by the blue curves. The vertical bars on the points represent the statistical uncertainties in the data, and the green bands show the total uncertainties in the background predictions. The lower panels give the ratios of the observed to the predicted distributions, with the green bands representing the total uncertainty in the ratios.

Summary

In summary, results of a search for the exotic Higgs boson decay H

$\rightarrow \mathcal{A}\mathcal{A} \rightarrow 4\gamma$ have been presented. Events reconstructed with two photons are used, where each photon is assumed to be a misreconstructed, merged

$\mathcal{A} \rightarrow \gamma\gamma$ candidate. The first direct probe of the invariant mass spectrum of merged

$\mathcal{A} \rightarrow \gamma\gamma$ candidates is performed to discriminate potential signal events from the SM background. No excess of events above the estimated background is found. Upper limits on the branching fraction

$\mathcal{B}(\mathrm{H} \rightarrow \mathcal{A}\mathcal{A} \rightarrow 4\gamma)$ of 0.9--3.3

$\times$ 10

$^{-3}$ are set at the 95% confidence level for masses of

$\mathcal{A}$ in the range 0.1

$< m_{\mathcal{A}} <$ 1.2 GeV, assuming prompt

$\mathcal{A}$ decays.

References
1	CMS Collaboration	Combined measurements of Higgs boson couplings in proton-proton collisions at $\sqrt{s}=$ 13 TeV	EPJC 79 (2019) 421	CMS-HIG-17-031 1809.10733
2	D. Curtin et al.	Exotic decays of the 125 GeV Higgs boson	PRD 90 (2014) 075004	1312.4992
3	D. Curtin, R. Essig, S. Gori, and J. Shelton	Illuminating dark photons with high-energy colliders	JHEP 02 (2015) 157	1412.0018
4	R. D. Peccei and H. R. Quinn	$\mathrm{CP}$ conservation in the presence of pseudoparticles	PRL 38 (1977) 1440
5	M. Bauer, M. Neubert, and A. Thamm	Collider probes of axion-like particles	JHEP 12 (2017) 044	1708.00443
6	R. D. Peccei	The strong CP problem and axions	in Axions, M. Kuster, G. Raffelt, and B. Beltran, eds Springer Berlin Heidelberg	hep-ph/0607268
7	CMS Collaboration	Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state of two muons and two $\tau$ leptons in proton-proton collisions at $\sqrt{s}=$ 13 TeV	JHEP 11 (2018) 018	CMS-HIG-17-029 1805.04865
8	CMS Collaboration	A search for pair production of new light bosons decaying into muons in proton-proton collisions at 13 TeV	PLB 796 (2019) 131	CMS-HIG-18-003 1812.00380
9	CMS Collaboration	Search for light pseudoscalar boson pairs produced from decays of the 125 GeV Higgs boson in final states with two muons and two nearby tracks in pp collisions at $\sqrt{s}=$ 13 TeV	PLB 800 (2020) 135087	CMS-HIG-18-006 1907.07235
10	CMS Collaboration	Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state with two muons and two b quarks in pp collisions at 13 TeV	PLB 795 (2019) 398	CMS-HIG-18-011 1812.06359
11	CMS Collaboration	Search for a light pseudoscalar Higgs boson in the boosted $\mu\mu\tau\tau$ final state in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JHEP 08 (2020) 139	CMS-HIG-18-024 2005.08694
12	B. A. Dobrescu, G. Landsberg, and K. T. Matchev	Higgs boson decays to $\mathrm{CP}$ -odd scalars at the Fermilab Tevatron and beyond	PRD 63 (2001) 075003	hep-ph/0005308
13	P. W. Graham et al.	Experimental searches for the axion and axion-like particles	Annu. Rev. Nucl. Part. Sci. 65 (2015) 485	1602.00039
14	I. G. Irastorza and J. Redondo	New experimental approaches in the search for axion-like particles	Prog. Part. NP 102 (2018) 89	1801.08127
15	Particle Data Group Collaboration	Review of particle physics	PTEP 2020 (2020) 083C01
16	GlueX Collaboration	Search for photoproduction of axion-like particles at GlueX	2021	2109.13439
17	S. Knapen, T. Lin, H. K. Lou, and T. Melia	Searching for axionlike particles with ultraperipheral heavy-ion collisions	PRL 118 (2017) 171801	1607.06083
18	G. G. Raffelt	Astrophysical axion bounds	in Axions, M. Kuster, G. Raffelt, and B. Beltran, eds Springer Berlin Heidelberg	hep-ph/0611350
19	P. Sikivie	Axion cosmology	in Axions, M. Kuster, G. Raffelt, and B. Beltran, eds Springer Berlin Heidelberg	astro-ph/0610440
20	D. J. E. Marsh	Axion cosmology	Phys. Rep. 643 (2016) 1	1510.07633
21	F. Chadha-Day, J. Ellis, and D. J. E. Marsh	Axion dark matter: What is it and why now?	2021	2105.01406
22	ATLAS Collaboration	Search for a Higgs boson decaying to four photons through light $\mathrm{CP}$ -odd scalar coupling using 4.9 fb $^{-1}$ of 7 TeV pp collision data taken with ATLAS detector at the LHC	ATLAS-CONF-2012-079