More Like this

1. Measurement of differential ZZ + jets production cross sections in pp collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP10(2024)209  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Escalante_Del_Valle, A; Hussain, P S; et al (October 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> Diboson production in association with jets is studied in the fully leptonic final states, pp → (Z/γ^*)(Z/γ^*) + jets → 2ℓ2ℓ′ + jets, (ℓ,ℓ′ = e orμ) in proton-proton collisions at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb⁻¹collected with the CMS detector at the LHC. Differential distributions and normalized differential cross sections are measured as a function of jet multiplicity, transverse momentump_T, pseudorapidityη, invariant mass and ∆ηof the highest-p_Tand second-highest-p_Tjets, and as a function of invariant mass of the four-lepton system for events with various jet multiplicities. These differential cross sections are compared with theoretical predictions that mostly agree with the experimental data. However, in a few regions we observe discrepancies between the predicted and measured values. Further improvement of the predictions is required to describe the ZZ+jets production in the whole phase space. 

   more » « less
2. Search for dark matter produced in association with a dark Higgs boson decaying into W+W− in the one-lepton final state at $$ \sqrt{s} $$ = 13 TeV using 139 fb−1 of pp collisions recorded with the ATLAS detector

   https://doi.org/10.1007/JHEP07(2023)116  

   Aad, G.; Abbott, B.; Abbott, D. C.; Abeling, K.; Abidi, S. H.; Aboulhorma, A.; Abramowicz, H.; Abreu, H.; Abulaiti, Y.; Abusleme Hoffman, A. C.; et al (July 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> Several extensions of the Standard Model predict the production of dark matter particles at the LHC. A search for dark matter particles produced in association with a dark Higgs boson decaying intoW⁺W⁻in the$$ {\ell}^{\pm}\nu q{\overline{q}}^{\prime }, $$ ${\ell }^{\pm }\mathrm{\nu q}{\overline{q}}^{\prime },$final states withℓ=e, μis presented. This analysis uses 139 fb⁻¹ofppcollisions recorded by the ATLAS detector at a centre-of-mass energy of 13 TeV. TheW^±→$$ q\overline{q^{\prime }} $$ $q\overline{q\prime }$decays are reconstructed from pairs of calorimeter-measured jets or from track-assisted reclustered jets, a technique aimed at resolving the dense topology from a pair of boosted quarks using jets in the calorimeter and tracking information. The observed data are found to agree with Standard Model predictions. Scenarios with dark Higgs boson masses ranging between 140 and 390 GeV are excluded. 

   more » « less
3. Search for Higgs boson decays to a Z boson and a photon in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP05(2023)233  

   Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Escalante Del Valle, A.; Frühwirth, R.; Jeitler, M.; et al (May 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> Results are presented from a search for the Higgs boson decay H→Zγ, where Z→ ℓ⁺ℓ⁻withℓ= e or μ. The search is performed using a sample of proton-proton (pp) collision data at a center-of-mass energy of 13 TeV, recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb⁻¹. Events are assigned to mutually exclusive categories, which exploit differences in both event topology and kinematics of distinct Higgs production mechanisms to enhance signal sensitivity. The signal strengthμ, defined as the product of the cross section and the branching fraction$$ \left[\sigma \left(\textrm{pp}\to \textrm{H}\right)\mathcal{B}\left(\textrm{H}\to \textrm{Z}\upgamma \right)\right] $$ $\left(\sigma \left(\mathrm{pp}\to H\right)B\left(H\to \mathrm{Z\gamma }\right)\right)$relative to the standard model prediction, is extracted from a simultaneous fit to theℓ⁺ℓ⁻γ invariant mass distributions in all categories and is measured to beμ= 2.4 ± 0.9 for a Higgs boson mass of 125.38 GeV. The statistical significance of the observed excess of events is 2.7 standard deviations. This measurement corresponds to$$ \left[\sigma \left(\textrm{pp}\to \textrm{H}\right)\mathcal{B}\left(\textrm{H}\to \textrm{Z}\upgamma \right)\right]=0.21\pm 0.08 $$ $\left(\sigma \left(\mathrm{pp}\to H\right)B\left(H\to \mathrm{Z\gamma }\right)\right)=0.21\pm 0.08$pb. The observed (expected) upper limit at 95% confidence level onμis 4.1 (1.8), where the expected limit is calculated under the background-only hypothesis. The ratio of branching fractions$$ \mathcal{B}\left(\textrm{H}\to \textrm{Z}\upgamma \right)/\mathcal{B}\left(\textrm{H}\to \upgamma \upgamma \right) $$ $B\left(H\to \mathrm{Z\gamma }\right)/B\left(H\to \mathrm{\gamma \gamma }\right)$is measured to be$$ {1.5}_{-0.6}^{+0.7} $$ ${1.5}_{-0.6}^{+0.7}$, which agrees with the standard model prediction of 0.69 ± 0.04 at the 1.5 standard deviation level. 

   more » « less
4. Search for dark matter particles in W+W− events with transverse momentum imbalance in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP03(2024)134  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Escalante_Del_Valle, A; Hussain, P S; et al (March 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> 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 (ℓ= 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 theℓνqq and 2ℓ2νfinal 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. 

   more » « less
5. Multiplicity-dependent production of Σ(1385)± and Ξ(1530)0 in pp collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP05(2024)317  

   Acharya, S; Adamová, D; Aglieri_Rinella, G; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; Akindinov, A; et al (May 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> The production yields of the Σ(1385)^±and Ξ(1530)⁰resonances are measured in pp collisions at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV with ALICE. The measurements are performed as a function of the charged-particle multiplicity ⟨dN_ch/dη⟩, which is related to the energy density produced in the collision. The results include transverse momentum (p_T) distributions,p_T-integrated yields, mean transverse momenta of Σ(1385)^±and Ξ(1530)⁰, as well as ratios of thep_T-integrated resonance yields relative to yields of other hadron species. The Σ(1385)^±/π^±and Ξ(1530)⁰/π^±yield ratios are consistent with the trend of the enhancement of strangeness production from low to high multiplicity pp collisions, which was previously observed for strange and multi-strange baryons. The yield ratio between the measured resonances and the long-lived baryons with the same strangeness content exhibits a hint of a mild increasing trend at low multiplicity, despite too large uncertainties to exclude the flat behaviour. The results are compared with predictions from models such as EPOS-LHC and PYTHIA 8 with Rope shoving. The latter provides the best description of the multiplicity dependence of the Σ(1385)^±and Ξ(1530)⁰production in pp collisions at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV. 

   more » « less