Date

Version 2
Searches for hidden sectors using $K^+\toπ^+X$ decays

The NA62 collaboration Cortina Gil, Eduardo ; Jerhot, Jan ; Minucci, Elisa ; et al.
JHEP 11 (2025) 143, 2025.
Inspire Record 2953428 DOI 10.17182/hepdata.160245

Results from the study of the rare decays $K^+\toπ^+ν\barν$, $K^{+}\rightarrowπ^{+}μ^{+}μ^{-}$ and $K^{+}\rightarrowπ^{+}γγ$ at the NA62 experiment at CERN are interpreted in terms of improved limits for $\rm{B}(K^+\toπ^+X)$ and coupling parameters of hidden-sector models, where $X$ is a mediator. World-leading limits are achieved for dark photon, dark scalar and axion-like particle models.

50 data tables

Number of expected and observed events as a function of squared missing mass.

Number of expected and observed events as a function of squared missing mass.

Single Event Sensitivity (SES) for the $K^{+}\rightarrow\pi^{+}X$ search as a function of X mass.

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Cross sections of $\eta$ mesons in $p$ $+$ $p$ collisions at forward rapidity at $\sqrt{s}=500$ GeV and central rapidity at $\sqrt{s}=510$ GeV

The PHENIX collaboration Abdulameer, N.J. ; Acharya, U. ; Adare, A. ; et al.
2025.
Inspire Record 2943245 DOI 10.17182/hepdata.166316

We present the first measurements of the forward and midrapidity $η$-meson cross sections from $p$$+$$p$ collisions at $\sqrt{s}=500$ and $510$~GeV, respectively. We also report the midrapidity $η/π^0$ ratio at 510 GeV. The forward cross section is measured differentially in $η$-meson transverse momentum ($p_T$) from 1.0 to 6.5~GeV/$c$ for pseudorapidity $3.0<|η|<3.8$. The midrapidity cross section is measured from 3.5 to 44 GeV/$c$ for pseudorapidity $|η|<0.35$. Both cross sections serve as critical inputs to an updated global analysis of the $η$-meson fragmentation functions.

5 data tables

The invariant differential cross section of $\eta$ mesons at forward rapidity in pp collisions at center-of-mass energy 500 GeV.

The invariant differential cross section of $\eta$ mesons at central rapidity in pp collisions at center-of-mass energy 510 GeV.

The ratio of $\eta$ to $\pi^0$ cross sections at central rapidity in pp collisions at center-of-mass energy 510 GeV.

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Revealing the microscopic mechanism of deuteron formation at the LHC

The ALICE collaboration Acharya, S. ; Agarwal, A. ; Aglieri Rinella, G. ; et al.
Nature 648 (2025) 306-311, 2025.
Inspire Record 2907586 DOI 10.17182/hepdata.165804

The formation of light (anti)nuclei with mass number A of a few units (e.g., d, $^3$He, and $^4$He) in high-energy hadronic collisions presents a longstanding mystery in nuclear physics [1,2]. It is not clear how nuclei bound by a few MeV can emerge in environments characterized by temperatures above 100 MeV [3-5], about 100,000 times hotter than the center of the Sun. Despite extensive studies, this question remained unanswered. The ALICE Collaboration now addresses it with a novel approach using deuteron-pion momentum correlations in proton-proton (pp) collisions at the Large Hadron Collider (LHC). Our results provide model-independent evidence that about 80% of the observed (anti)deuterons are produced in nuclear fusion reactions [6] following the decay of short-lived resonances, such as the $\Delta (1232)$. These findings resolve a crucial gap in our understanding of nucleosynthesis in hadronic collisions. Beyond answering the fundamental question on how nuclei are formed in hadronic collisions, the results can be employed in the modeling of the production of light and heavy nuclei in cosmic rays [7] and dark matter decays [8,9].

7 data tables

Measured $\pi^{+}$–d$\oplus\pi^{-}$–$\overline{\mathrm{d}}$ (left panel) correlation function.

Measured $\pi^{-}$–d$\oplus\pi^{+}$–$\overline{\mathrm{d}}$ (right panel) correlation function.

The extracted kinetic decoupling temperature is derived from $\pi^{+}$–d correlation functions.

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Observation of WZ$\gamma$ production and constraints on new physics scenarios in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration Chekhovsky, V. ; Hayrapetyan, A. ; Makarenko, V. ; et al.
Phys.Rev.D 112 (2025) 012009, 2025.
Inspire Record 2905870 DOI 10.17182/hepdata.157601

A measurement of the WZ$γ$ triboson production cross section is presented. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis focuses on the final state with three charged leptons, $\ell^\pmν\ell^+\ell^-$, where $\ell$ = e or $μ$, accompanied by an additional photon. The observed (expected) significance of the WZ$γ$ signal is 5.4 (3.8) standard deviations. The cross section is measured in a fiducial region, where events with an $\ell$ originating from a tau lepton decay are excluded, to be 5.48 $\pm$ 1.11 fb, which is compatible with the prediction of 3.69 $\pm$ 0.24 fb at next-to-leading order in quantum chromodynamics. Exclusion limits are set on anomalous quartic gauge couplings and on the production cross sections of massive axion-like particles.

6 data tables

The distributions of the variables used in the simultaneous fit for the nonprompt $l$ CR. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The last bin of each plot has been extended to include the overflow contribution.

The distributions of the variables used in the simultaneous fit for the nonprompt $\gamma$ CR. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The last bin of each plot has been extended to include the overflow contribution.

The distributions of the variables used in the simultaneous fit for the ZZ CR. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The last bin of each plot has been extended to include the overflow contribution.

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Search for hadronic decays of feebly-interacting particles at NA62

The NA62 collaboration Cortina Gil, Eduardo ; Jerhot, Jan ; Lurkin, Nicolas ; et al.
Eur.Phys.J.C 85 (2025) 571, 2025.
Inspire Record 2877075 DOI 10.17182/hepdata.156981

The NA62 experiment at CERN has the capability to collect data in a beam-dump mode, where 400 GeV protons are dumped on an absorber. In this configuration, New Physics particles, including dark photons, dark scalars, and axion-like particles, may be produced in the absorber and decay in the instrumented volume beginning approximately 80 m downstream of the dump. A search for these particles decaying in flight to hadronic final states is reported, based on an analysis of a sample of $1.4 \times 10^{17}$ protons on dump collected in 2021. No evidence of a New Physics signal is observed, excluding new regions of parameter spaces of multiple models.

66 data tables

90% CL upper limit in dark photon coupling vs mass parameter space for combined di-lepton and hadronic final states, using bremsstrahlung production without the time-like form factor.

90% CL upper limit in dark photon coupling vs mass parameter space for combined di-lepton and hadronic final states, including mixing and bremsstrahlung production with a time-like form factor.

90% CL upper limit in dark scalar coupling vs mass parameter space for combined di-lepton and hadronic final states.

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Measurement of $J/\psi$ and $\psi\left(2S\right)$ production in $p+p$ and $p+d$ interactions at 120 GeV

The SeaQuest collaboration Leung, C.H. ; Nagai, K. ; Nakano, K. ; et al.
Phys.Lett.B 858 (2024) 139032, 2024.
Inspire Record 2799214 DOI 10.17182/hepdata.167075

We report the $p+p$ and $p+d$ differential cross sections measured in the SeaQuest experiment for $J/\psi$ and $\psi\left(2S\right)$ production at 120 GeV beam energy covering the forward $x$-Feynman ($x_F$) range of $0.5 < x_F <0.9$. The measured cross sections are in good agreement with theoretical calculations based on the nonrelativistic QCD (NRQCD) using the long-distance matrix elements deduced from a recent global analysis of proton- and pion-induced charmonium production data. The $\sigma_{\psi\left(2S\right)} / \sigma_{J/\psi}$ cross section ratios are found to increase as $x_F$ increases, indicating that the $q \bar{q}$ annihilation process has larger contributions in the $\psi\left(2S\right)$ production than the $J/\psi$ production. The $\sigma_{pd}/2\sigma_{pp}$ cross section ratios are observed to be significantly different for the Drell-Yan process and $J/\psi$ production, reflecting their different production mechanisms. We find that the $\sigma_{pd}/2\sigma_{pp}$ ratios for $J/\psi$ production at the forward $x_F$ region are sensitive to the $\bar{d}/ \bar{u}$ flavor asymmetry of the proton sea, analogous to the Drell-Yan process. The transverse momentum ($p_T$) distributions for $J/\psi$ and $\psi\left(2S\right)$ production are also presented and compared with data collected at higher center-of-mass energies.

12 data tables

The differential cross sections per nucleon, $d\sigma/dx_{F}$ (in nb), for $J/\psi$ production in $p+p$ collision at 120 GeV for different $x_F$ bins.

The differential cross sections per nucleon, $d\sigma/dx_{F}$ (in nb), for $J/\psi$ production in $p+d$ collision at 120 GeV for different $x_F$ bins.

The differential cross sections per nucleon, $d\sigma/dx_{F}$ (in nb), for $\psi(2S)$ production in $p+p$ collision at 120 GeV for different $x_F$ bins.

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Jet modification via $\pi^0$-hadron correlations in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

The PHENIX collaboration Abdulameer, N.J. ; Acharya, U. ; Adare, A. ; et al.
Phys.Rev.C 110 (2024) 044901, 2024.
Inspire Record 2797343 DOI 10.17182/hepdata.159378

High-momentum two-particle correlations are a useful tool for studying jet-quenching effects in the quark-gluon plasma. Angular correlations between neutral-pion triggers and charged hadrons with transverse momenta in the range 4--12~GeV/$c$ and 0.5--7~GeV/$c$, respectively, have been measured by the PHENIX experiment in 2014 for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$~GeV. Suppression is observed in the yield of high-momentum jet fragments opposite the trigger particle, which indicates jet suppression stemming from in-medium partonic energy loss, while enhancement is observed for low-momentum particles. The ratio and differences between the yield in Au$+$Au collisions and $p$$+$$p$ collisions, $I_{AA}$ and $\Delta_{AA}$, as a function of the trigger-hadron azimuthal separation, $\Delta\phi$, are measured for the first time at the Relativistic Heavy Ion Collider. These results better quantify how the yield of low-$p_T$ associated hadrons is enhanced at wide angle, which is crucial for studying energy loss as well as medium-response effects.

29 data tables

Per-trigger jet-pair yield as a function of $\Delta\phi$ for selected $\pi^0$ trigger and charged-hadron-associated $p_T$ combinations (${{p_{T,\pi^0}} \otimes p_{T,h}}$) in Au$+$Au collisions. Systematic uncertainties for background subtraction and global scale uncertainties are given.

Integrated away-side $I_{AA}$ as a function of $p_T^h$. Systematic uncertainties for background subtraction and global scale uncertainties are given.

Differential away-side a function of Deltaphi 0%-20% collisions. Systematic uncertainties for background subtraction and global scale uncertainties are given.

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Improved measurements of the Dalitz decays $\eta/\eta'\rightarrow\gamma e^{+}e^{-}$

The BESIII collaboration Ablikim, M. ; Achasov, M.N. ; Adlarson, P. ; et al.
Phys.Rev.D 109 (2024) 072001, 2024.
Inspire Record 2747714 DOI 10.17182/hepdata.157334

Based on a data sample of 10 billion $J/\psi$ events collected with the BESIII detector, improved measurements of the Dalitz decays $\eta/\eta'\rightarrow\gamma e^+e^-$ are performed, where the $\eta$ and $\eta'$ are produced through the radiative decays $J/\psi\rightarrow\gamma \eta/\eta'$. The branching fractions of $\eta\rightarrow\gamma e^+e^-$ and $\eta'\rightarrow\gamma e^+e^-$ are measured to be $(7.07 \pm 0.05 \pm 0.23)\times10^{-3}$ and $(4.83\pm0.07\pm0.14)\times10^{-4}$, respectively. Within the single pole model, the parameter of electromagnetic transition form factor for $\eta\rightarrow\gamma e^+e^-$ is determined to be $\Lambda_{\eta}=(0.749 \pm 0.027 \pm 0.007)~ {\rm GeV}/c^{2}$. Within the multi-pole model, we extract the electromagnetic transition form factors for $\eta'\rightarrow\gamma e^+e^-$ to be $\Lambda_{\eta'} = (0.802 \pm 0.007\pm 0.008)~ {\rm GeV}/c^{2}$ and $\gamma_{\eta'} = (0.113\pm0.010\pm0.002)~ {\rm GeV}/c^{2}$. The results are consistent with both theoretical predictions and previous measurements. The characteristic sizes of the interaction regions for the $\eta$ and $\eta'$ are calculated to be $(0.645 \pm 0.023 \pm 0.007 )~ {\rm fm}$ and $(0.596 \pm 0.005 \pm 0.006)~ {\rm fm}$, respectively. In addition, we search for the dark photon in $\eta/\eta^\prime\rightarrow\gamma e^{+}e^{-}$, and the upper limits of the branching fractions as a function of the dark photon are given at 90% confidence level.

2 data tables

The binned invariant mass spectrum of $e^+e^-$ pairs produced from the $\eta\to \gamma e^+e^-$ transition. The efficiency-corrected and background-subtracted data are binned in M($e^+e^-$) and the number of events in each bin is shown.

The binned invariant mass spectrum of $e^+e^-$ pairs produced from the $\eta^\prime\to \gamma e^+e^-$ transition. The efficiency-corrected and background-subtracted data are binned in M($e^+e^-$) and the number of events in each bin is shown.


Version 2
Search for leptonic decays of the dark photon at NA62

The NA62 collaboration Cortina Gil, Eduardo ; Jerhot, Jan ; Kleimenova, Alina ; et al.
Phys.Rev.Lett. 133 (2024) 111802, 2024.
Inspire Record 2738578 DOI 10.17182/hepdata.154438

The NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of $1.4\times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. The combined result for dark photon searches in lepton-antilepton final states is presented and a region of the parameter space is excluded at 90% CL, improving on previous experimental limits for dark photon mass values between 50 and 600 MeV$/c^2$ and coupling values in the range $10^{-6}$ to $4\times10^{-5}$. An interpretation of the $e^+ e^-$ search result in terms of the emission and decay of an axion-like particle is also presented.

6 data tables

90% CL upper limit in dark photon coupling vs mass parameter space for the $A^\prime \rightarrow e^+e^-$ analysis.

90% CL upper limit in dark photon coupling vs mass parameter space for the $A^\prime \rightarrow e^+e^-$ analysis.

90% CL upper limit in dark photon coupling vs mass parameter space for the $A^\prime \rightarrow l^+l^-$ analysis.

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Version 2
Measurement of the $K^+\to\pi^+\gamma\gamma$ decay

The NA62 collaboration Cortina Gil, Eduardo ; Minucci, Elisa ; Padolski, Sergey ; et al.
Phys.Lett.B 850 (2024) 138513, 2024.
Inspire Record 2718968 DOI 10.17182/hepdata.147259

A sample of 3984 candidates of the $K^+\to\pi^+\gamma\gamma$ decay, with an estimated background of $291\pm14$ events, was collected by the NA62 experiment at CERN during 2017-2018. In order to describe the observed di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be $(9.61\pm0.17)\times10^{-7}$. The first search for production and prompt decay of an axion-like particle with gluon coupling in the process $K^+\to\pi^+a$, $a\to\gamma\gamma$ is also reported.

10 data tables

See caption of Figure 6.

See caption of Figure 6.

Upper limits at 90% CL of $B(K^+\to\pi^+a)\times B(a\to\gamma\gamma)$ in the prompt ALP decay assumption.

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