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Search for narrow trijet resonances in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration Hayrapetyan, Aram ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
Phys.Rev.Lett. 133 (2024) 011801, 2024.
Inspire Record 2713513 DOI 10.17182/hepdata.144165

The first search for singly produced narrow resonances decaying to three well-separated hadronic jets is presented. The search uses proton-proton collision data corresponding to an integrated luminosity of 138 fb$^{-1}$ at $\sqrt{s}$ = 13 TeV, collected at the CERN LHC. No significant deviations from the background predictions are observed between 1.75-9.00 TeV. The results provide the first mass limits on a right-handed boson Z$_{\mathrm{R}}$ decaying to three gluons and on an excited quark decaying via a vector boson to three quarks, as well as updated limits on a Kaluza-Klein gluon decaying via a radion to three gluons.

35 data tables

Observed and expected (background-only fitted) invariant mass spectra of trijet events. Data spectra from three years are fitted separately and the sum is shown in the figure. The fitting function used is ${ d N}/{ d m} = p_{0}(1-x)^{p_{1}}/x^{\sum_{i=2}^{3} p_{i}\log^{i-2}(x)}$. The fitted parameters are $p_{1} = 7.350, p_{2} = 6.926, p_{3} = 0.388$ for 2016, $p_{1} = 8.308, p_{2} = 5.931, p_{3} = 0.167$ for 2017 and $p_{1} = 8.770, p_{2} = 5.617, p_{3} = 0.106$ for 2018. $p_{0}$ is the normalization parameter and its exact value is irrelevant.

Expected and observed limits at 95% CL on $\sigma \mathcal{B} (X \to ggg) \mathcal{A}$ for a 3-body decay trijet resonance with $\Gamma_{X}\sim 3\% m_{X}$. The acceptance $\mathcal{A}$ is defined as $\mathcal{A} = N$(events with $m_{X}^{GEN} > 85\% m_{X}^{input}$) / $N$(events generated in the full phase space defined by the CMS default generator settings). Only 2016 data are used to derive limits below 2.0 TeV because of higher trigger thresholds in 2017 and 2018. Theoretical predictions assuming SM-like couplings are depicted with the red curve.

Expected and observed limits at 95% CL on $\sigma \mathcal{B} (X \to ggg) \mathcal{A}$ for a 3-body decay trijet resonance with $\Gamma_{X}\sim 0.01\% m_{X}$. The acceptance $\mathcal{A}$ is defined as $\mathcal{A} = N$(events with $m_{X}^{GEN} > 85\% m_{X}^{input}$) / $N$(events generated in the full phase space defined by the CMS default generator settings). Only 2016 data are used to derive limits below 2.0 TeV because of higher trigger thresholds in 2017 and 2018. Theoretical predictions are depicted with the red curve.

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Estimate of Background Baseline and Upper Limit on the Chiral Magnetic Effect in Isobar Collisions at $\sqrt{s_{\text{NN}}}=200$ GeV at the Relativistic Heavy-Ion Collider

The STAR collaboration Abdulhamid, M.I. ; Aboona, B.E. ; Adam, J. ; et al.
Phys.Rev.C 110 (2024) 014905, 2024.
Inspire Record 2713075 DOI 10.17182/hepdata.145133

For the search of the chiral magnetic effect (CME), STAR previously presented the results from isobar collisions (${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$, ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) obtained through a blind analysis. The ratio of results in Ru+Ru to Zr+Zr collisions for the CME-sensitive charge-dependent azimuthal correlator ($\Delta\gamma$), normalized by elliptic anisotropy ($v_{2}$), was observed to be close to but systematically larger than the inverse multiplicity ratio. The background baseline for the isobar ratio, $Y = \frac{(\Delta\gamma/v_{2})^{\text{Ru}}}{(\Delta\gamma/v_{2})^{\text{Zr}}}$, is naively expected to be $\frac{(1/N)^{\text{Ru}}}{(1/N)^{\text{Zr}}}$; however, genuine two- and three-particle correlations are expected to alter it. We estimate the contributions to $Y$ from those correlations, utilizing both the isobar data and HIJING simulations. After including those contributions, we arrive at a final background baseline for $Y$, which is consistent with the isobar data. We extract an upper limit for the CME fraction in the $\Delta\gamma$ measurement of approximately $10\%$ at a $95\%$ confidence level on in isobar collisions at $\sqrt{s_{\text{NN}}} = 200$ GeV, with an expected $15\%$ difference in their squared magnetic fields.

39 data tables

Figure 1a, upper panel, full-event

Figure 1a, lower panel, full-event

Figure 1b, upper panel, subevent

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Studies of new Higgs boson interactions through nonresonant $HH$ production in the $b\bar{b}\gamma\gamma$ final state in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 01 (2024) 066, 2024.
Inspire Record 2712676 DOI 10.17182/hepdata.144918

A search for nonresonant Higgs boson pair production in the $b\bar{b}\gamma\gamma$ final state is performed using 140 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. This analysis supersedes and expands upon the previous nonresonant ATLAS results in this final state based on the same data sample. The analysis strategy is optimised to probe anomalous values not only of the Higgs ($H$) boson self-coupling modifier $\kappa_\lambda$ but also of the quartic $HHVV$ ($V=W,Z$) coupling modifier $\kappa_{2V}$. No significant excess above the expected background from Standard Model processes is observed. An observed upper limit $\mu_{HH}<4.0$ is set at 95% confidence level on the Higgs boson pair production cross-section normalised to its Standard Model prediction. The 95% confidence intervals for the coupling modifiers are $-1.4<\kappa_\lambda<6.9$ and $-0.5<\kappa_{2V}<2.7$, assuming all other Higgs boson couplings except the one under study are fixed to the Standard Model predictions. The results are interpreted in the Standard Model effective field theory and Higgs effective field theory frameworks in terms of constraints on the couplings of anomalous Higgs boson (self-)interactions.

45 data tables

Observed (solid line) value of $-2\ln\Lambda$ as a function of $\kappa_{\lambda}$, when all other coupling modifiers are fixed to their SM predictions.

Expected (dashed line) value of $-2\ln\Lambda$ as a function of $\kappa_{\lambda}$, when all other coupling modifiers are fixed to their SM predictions.

Observed (solid line) value of $-2\ln\Lambda$ as a function of $\kappa_{2V}$, when all other coupling modifiers are fixed to their SM predictions.

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Search for dark matter particles in W$^+$W$^-$ events with transverse momentum imbalance in proton-proton collisions at $\sqrt{s}$ = 13 TeV

The CMS collaboration Hayrapetyan, Aram ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
JHEP 03 (2024) 134, 2024.
Inspire Record 2712865 DOI 10.17182/hepdata.139719

A search for dark matter particles is performed using events with a pair of W bosons and large missing transverse momentum. Candidate events are selected by requiring one or two leptons ($\ell =$ electrons or muons). The analysis is based on proton-proton collision data collected at a center-of-mass energy of 13 TeV by the CMS experiment at the LHC and corresponding to an integrated luminosity of 138 fb$^{-1}$. No significant excess over the expected standard model background is observed in the $\ell\nu$qq and 2$\ell$2$\nu$ final states of the W$^+$W$^-$ boson pair. Limits are set on dark matter production in the context of a simplified dark Higgs model, with a dark Higgs boson mass above the W$^+$W$^-$ mass threshold. The dark matter phase space is probed in the mass range 100-300 GeV, extending the scope of previous searches. Current exclusion limits are improved in the range of dark Higgs masses from 160 to 250 GeV, for a dark matter mass of 200 GeV.

61 data tables

Leading lepton $p_T$ pre-fit distribution for selected events in SR1 of the di-leptonic channel for the full dataset. The error bars on the data points represent the statistical uncertainty of the data, and the error bars on the predicted yields represent the combined systematic and statistical uncertainty in each bin. The signal prediction represents the mass point: $m_s = 160 GeV, m_{\chi} = 100 GeV, m_{Z'} = 500 GeV$. The last bin includes the overflow.

Trailing lepton $p_T$ pre-fit distribution for selected events in SR1 of the di-leptonic channel for the full dataset. The error bars on the data points represent the statistical uncertainty of the data, and the error bars on the predicted yields represent the combined systematic and statistical uncertainty in each bin. The signal prediction represents the mass point: $m_s = 160 GeV, m_{\chi} = 100 GeV, m_{Z'} = 500 GeV$. The last bin includes the overflow.

Missing $p_T$ pre-fit distribution for selected events in SR2 of the di-leptonic channel for the full dataset. The error bars on the data points represent the statistical uncertainty of the data, and the error bars on the predicted yields represent the combined systematic and statistical uncertainty in each bin. The signal prediction represents the mass point: $m_s = 160 GeV, m_{\chi} = 100 GeV, m_{Z'} = 500 GeV$. The last bin includes the overflow.

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Search for central exclusive production of top quark pairs in proton-proton collisions at $\sqrt{s}$ = 13 TeV with tagged protons

The CMS & TOTEM collaborations Tumasyan, Armen ; Adam, Wolfgang ; Andrejkovic, Janik Walter ; et al.
JHEP 06 (2024) 187, 2024.
Inspire Record 2140837 DOI 10.17182/hepdata.127701

A search for the central exclusive production of top quark-antiquark pairs ($\mathrm{t\bar{t}}$) is performed for the first time using proton-tagged events in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 29.4 fb$^{-1}$. The $\mathrm{t\bar{t}}$ decay products are reconstructed using the central CMS detector, while forward protons are measured in the CMS-TOTEM precision proton spectrometer. An observed (expected) upper bound on the production cross section of 0.59 (1.14) pb is set at 95% confidence level, for collisions of protons with fractional momentum losses between 2 and 20%.

1 data table

Expected and observed 95% confidence level (CL) upper limits for the cross section of $\mathrm{pp} \rightarrow \mathrm{p t \bar{t} p}$, for the dilepton and $\ell+$jets channels separately and combined. The green and yellow bands show the 68 and 95% intervals, respectively, for the expected upper limit.


Study of $Z \to ll\gamma$ decays at $\sqrt s~$= 8 TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abbott, Dale ; et al.
Eur.Phys.J.C 84 (2024) 195, 2024.
Inspire Record 2712353 DOI 10.17182/hepdata.131524

This paper presents a study of $Z \to ll\gamma~$decays with the ATLAS detector at the Large Hadron Collider. The analysis uses a proton-proton data sample corresponding to an integrated luminosity of 20.2 fb$^{-1}$ collected at a centre-of-mass energy $\sqrt{s}$ = 8 TeV. Integrated fiducial cross-sections together with normalised differential fiducial cross-sections, sensitive to the kinematics of final-state QED radiation, are obtained. The results are found to be in agreement with state-of-the-art predictions for final-state QED radiation. First measurements of $Z \to ll\gamma\gamma$ decays are also reported.

77 data tables

Unfolded $M(l^{+}\gamma)$ distribution for $Z \to ee\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 63717.4 $\pm$ 252.4, NPowHeg truth =338714.

Unfolded $M(l^{-}\gamma)$ distribution for $Z \to ee\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 63855.8 $\pm$ 252.7 , NPowHeg truth =338708.

Unfolded $M(l^{+}\gamma)$ distribution for $Z \to \mu\mu\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 64809.8 $\pm$ 254.6, NPowHeg truth =634285.

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Search for non-resonant Higgs boson pair production in the $2b + 2\ell + E_\mathrm{T}^\mathrm{miss}$ final state in $pp$ collisions at $\sqrt{s} = 13\mathrm{TeV}$ with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
JHEP 02 (2024) 037, 2024.
Inspire Record 2711979 DOI 10.17182/hepdata.144917

A search for non-resonant Higgs boson pair ($HH$) production is presented, in which one of the Higgs bosons decays to a b-quark pair ($b\bar b$) and the other decays to $WW^*$, $ZZ^*$, or $\tau^+\tau^-$, with in each case a final state with $\ell^+\ell^- +$ neutrinos ($\ell = e, \mu$). The analysis targets separately the gluon-gluon fusion and vector boson fusion production modes. Data recorded by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of $140\mathrm{fb}^{-1}$, are used in this analysis. Events are selected to have exactly two $b$-tagged jets and two leptons with opposite electric charge and missing transverse momentum in the final state. These events are classified using multivariate analysis algorithms to separate the $HH$ events from other Standard Model processes. No evidence of the signal is found. The observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 9.7 (16.2) times the Standard Model prediction at 95% confidence level. The Higgs boson self-interaction coupling parameter $\kappa_\lambda$ and the quadrilinear coupling parameter $\kappa_{2V}$ are each separately constrained by this analysis to be within the ranges ${[-6.2, 13.3]}$ and ${[-0.17, 2.4]}$, respectively, at 95% confidence level, when all other parameters are fixed.

7 data tables

Pre-fit yields of the $t\bar{t}$, $Z$+HF and $Wt$ CRs, both for the ggF and VBF event selection, as well as the highest-score bins, numbered from high (VBF-SR 1 and ggF-SR 1) to low score (VBF-SR 5 and ggF-SR 7), of the BDT and DNN output distribution in the VBF and ggF event categories, respectively, as used in the final result. The shaded bands include both statistical and systematic uncertainties.

Post-fit yields from the signal+background fit of the $t\bar{t}$, $Z$+HF and $Wt$ CRs, both for the ggF and VBF event selections, as well as the highest-score bins, numbered from high (VBF-SR 1 and ggF-SR 1) to low score (VBF-SR 5 and ggF-SR 7), of the BDT and DNN output distribution in the VBF and ggF event categories respectively as used in the final result. The fit is a conditional fit with the signal strength fixed to the observed upper limit of $\mu_{HH} = 9.7$. The shaded bands include both statistical and systematic uncertainties.

Observed and expected upper limits on the ratios of the Higgs boson pair production cross-section to the corresponding Standard Model prediction $\sigma_{HH}/\sigma^\mathrm{SM}_{HH}$ for the ggF $HH$ signal only (top row), the VBF $HH$ signal only while considering ggF $HH$ as background (second row) and the combined ggF+VBF $HH$ signal considering only the ggF SR (third row) and considering all SRs (bottom row) at a 95% confidence level. The relative ratio between the ggF and VBF production modes is fixed to the SM value.

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Light-flavor particle production in high-multiplicity pp collisions at $\mathbf{\sqrt{\textit{s}} = 13}$ TeV as a function of transverse spherocity

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Aglieri Rinella, Gianluca ; et al.
JHEP 05 (2024) 184, 2024.
Inspire Record 2711421 DOI 10.17182/hepdata.153642

Results on the transverse spherocity dependence of light-flavor particle production ($\pi$, K, p, $\phi$, ${\rm K^{*0}}$, ${\rm K}^{0}_{\rm{S}}$, $\Lambda$, $\Xi$) at midrapidity in high-multiplicity pp collisions at $\sqrt{s} = 13$ TeV were obtained with the ALICE apparatus. The transverse spherocity estimator ($S_{{\rm O}}^{{\it p}_{\rm T}=1}$) categorizes events by their azimuthal topology. Utilizing narrow selections on $S_{\text{O}}^{{\it p}_{\rm T}=1}$, it is possible to contrast particle production in collisions dominated by many soft initial interactions with that observed in collisions dominated by one or more hard scatterings. Results are reported for two multiplicity estimators covering different pseudorapidity regions. The $S_{{\rm O}}^{{\it p}_{\rm T}=1}$ estimator is found to effectively constrain the hardness of the events when the midrapidity ($\left | \eta \right |< 0.8$) estimator is used. The production rates of strange particles are found to be slightly higher for soft isotropic topologies, and severely suppressed in hard jet-like topologies. These effects are more pronounced for hadrons with larger mass and strangeness content, and observed when the topological selection is done within a narrow multiplicity interval. This demonstrates that an important aspect of the universal scaling of strangeness enhancement with final-state multiplicity is that high-multiplicity collisions are dominated by soft, isotropic processes. On the contrary, strangeness production in events with jet-like processes is significantly reduced. The results presented in this article are compared with several QCD-inspired Monte Carlo event generators. Models that incorporate a two-component phenomenology, either through mechanisms accounting for string density, or thermal production, are able to describe the observed strangeness enhancement as a function of $S_{{\rm O}}^{{\it p}_{\rm T}=1}$.

45 data tables

Spherocity distributions with respect to different multiplicity selections.

<pT> vs <dN_{#pi}/dEta> for different multiplicity and spherocity classes.

pT differential Phi spectra as a function of spherocity within 0-1% nTracklets.

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Positronium laser cooling via the $1^3S$-$2^3P$ transition with a broadband laser pulse

The AEḡIS collaboration Glöggler, L.T. ; Gusakova, N. ; Rienäcker, B. ; et al.
Phys.Rev.Lett. 132 (2024) 083402, 2024.
Inspire Record 2710590 DOI 10.17182/hepdata.157580

We report on laser cooling of a large fraction of positronium (Ps) in free-flight by strongly saturating the $1^3S$-$2^3P$ transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived $3^3P$ states. The second effect is the one-dimensional Doppler cooling of Ps, reducing the cloud's temperature from 380(20) K to 170(20) K. We demonstrate a 58(9) % increase in the coldest fraction of the Ps ensemble.

5 data tables

SSPALS spectra of positronium in vacuum without lasers, with the 205 nm and 1064 nm lasers, with the 243 nm laser only, and with all three lasers 243 nm, 205 nm and 1064 nm. The 243 nm laser is firing during the time window from −20 to 50 ns, while the 205 nm and 1064 nm are injected 75 ns after positron implantation time (t = 0 ns). Each curve is an average of 90 individual spectra. The statistical error is smaller than the linewidths. For analysis, the spectra were integrated between 150 and 400 ns.

Ps velocity distribution measured by SSPALS. Transverse Doppler profile measured by two-photon resonant ionization. A Gaussian fit yields an rms width of 44(1) pm, which translates to a Ps rms velocity of 5.3 $\pm$ 0.2 × 10$^4$ m/s after deconvoluting the laser bandwidth.

Ps velocity distribution measured by SSPALS. Velocity-resolved increase in the number of ground state Ps atoms, induced by the 243 nm transitory excitation to the 2$^3$P level. At resonance, the expected Lamb dip is observed. A 2-Gaussian fit yields an rms width of the enveloping Gaussian of 44(3) pm, which corresponds to a Ps rms velocity of 4.9 $\pm$ 0.4 × 10$^4$ m/s.

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Femtoscopic correlations of identical charged pions and kaons in pp collisions at $\sqrt{s}=13$ TeV with event-shape selection

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Aglieri Rinella, Gianluca ; et al.
Phys.Rev.C 109 (2024) 024915, 2024.
Inspire Record 2709104 DOI 10.17182/hepdata.146805

Collective behavior has been observed in high-energy heavy-ion collisions for several decades. Collectivity is driven by the high particle multiplicities that are produced in these collisions. At the CERN Large Hadron Collider (LHC), features of collectivity have also been seen in high-multiplicity proton-proton collisions that can attain particle multiplicities comparable to peripheral Pb-Pb collisions. One of the possible signatures of collective behavior is the decrease of femtoscopic radii extracted from pion and kaon pairs emitted from high-multiplicity collisions with increasing pair transverse momentum. This decrease can be described in terms of an approximate transverse mass scaling. In the present work, femtoscopic analyses are carried out by the ALICE Collaboration on charged pion and kaon pairs produced in pp collisions at $\sqrt{s}=13$ TeV from the LHC to study possible collectivity in pp collisions. The event-shape analysis method based on transverse sphericity is used to select for spherical versus jet-like events, and the effects of this selection on the femtoscopic radii for both charged pion and kaon pairs are studied. This is the first time this selection method has been applied to charged kaon pairs. An approximate transverse-mass scaling of the radii is found in all multiplicity ranges studied when the difference in the Lorentz boost for pions and kaons is taken into account. This observation does not support the hypothesis of collective expansion of hot and dense matter that should only occur in high-multiplicity events. A possible alternate explanation of the present results is based on a scenario of common emission conditions for pions and kaons in pp collisions for the multiplicity ranges studied.

74 data tables
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