More Like this

1. Combination of Searches for Higgs Boson Pair Production in $pp$ Collisions at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS Detector

   https://doi.org/10.1103/PhysRevLett.133.101801  

   Aad, G; Aakvaag, E; Abbott, B; Abdelhameed, S; Abeling, K; Abicht, N J; Abidi, S H; Aboelela, M; Aboulhorma, A; Abramowicz, H; et al (September 2024, Physical Review Letters)

   This Letter presents results from a combination of searches for Higgs boson pair production using $126–140{\mathrm{fb}}^{-1}$ of proton-proton collision data at $\sqrt{s}=13\mathrm{TeV}$ recorded with the ATLAS detector. At 95% confidence level (CL), the upper limit on the production rate is 2.9 times the standard model (SM) prediction, with an expected limit of 2.4 assuming no Higgs boson pair production. Constraints on the Higgs boson self-coupling modifier ${\kappa }_{\lambda }={\lambda }_{HHH}/{\lambda }_{HHH}^{\mathrm{SM}}$ , and the quartic $HHVV$ coupling modifier ${\kappa }_{2V}=g_{HHVV}/g_{HHVV}^{\mathrm{SM}}$ , are derived individually, fixing the other parameter to its SM value. The observed 95% CL intervals are $-1.2<{\kappa }_{\lambda }<7.2$ and $0.6<{\kappa }_{2V}<1.5$ , respectively, while the expected intervals are $-1.6<{\kappa }_{\lambda }<7.2$ and $0.4<{\kappa }_{2V}<1.6$ in the SM case. Constraints obtained for several interaction parameters within Higgs effective field theory are the strongest to date, offering insights into potential deviations from SM predictions. © 2024 CERN, for the ATLAS Collaboration2024CERN 

   more » « less
2. Search for the nonresonant production of Higgs boson pairs via gluon fusion and vector-boson fusion in the $b\overline{b}{\tau }^{+}{\tau }^{-}$ final state in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS detector

   https://doi.org/10.1103/PhysRevD.110.032012  

   Aad, G; Aakvaag, E; Abbott, B; Abeling, K; Abicht, N J; Abidi, S H; Aboelela, M; Aboulhorma, A; Abramowicz, H; Abreu, H; et al (August 2024, Physical Review D)

   A search for the nonresonant production of Higgs boson pairs in the $HH\to b\overline{b}{\tau }^{+}{\tau }^{-}$ channel is performed using $140{\mathrm{fb}}^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The analysis strategy is optimized to probe anomalous values of the Higgs boson self-coupling modifier ${\kappa }_{\lambda }$ and 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 (expected) upper limit ${\mu }_{HH}<5.9\left(3.3\right)$ is set at 95% confidence-level on the Higgs boson pair production cross section normalized to its Standard Model prediction. The coupling modifiers are constrained to an observed (expected) 95% confidence interval of $-3.1<{\kappa }_{\lambda }<9.0$ ( $-2.5<{\kappa }_{\lambda }<9.3$ ) and $-0.5<{\kappa }_{2V}<2.7$ ( $-0.2<{\kappa }_{2V}<2.4$ ), assuming all other Higgs boson couplings are fixed to the Standard Model prediction. The results are also interpreted in the context of effective field theories via constraints on anomalous Higgs boson couplings and Higgs boson pair production cross sections assuming different kinematic benchmark scenarios. © 2024 CERN, for the ATLAS Collaboration2024CERN 

   more » « less
3. Measurement of the Higgs boson total decay width using the $H\to WW\to e\nu \mu \nu$ decay channel in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/rny9-zby1  

   Hayrapetyan, A; Makarenko, V; Tumasyan, A; Adam, W; Benato, L; Bergauer, T; Dragicevic, M; Hussain, P S; Jeitler, M; Krammer, N; et al (May 2026, Physical Review D)

   The Higgs boson (H) decay width is determined from the ratio of off- and on-shell production of $H\to WW\to e\nu \mu \nu$ using proton–proton collision data corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ collected at $\sqrt{s}=13\mathrm{TeV}$ by the CMS experiment at the Large Hadron Collider. The off-shell signal strength is measured as ${\mu }_{\mathrm{off}\text{−}\mathrm{shell}}={1.2}_{-0.7}^{+0.8}$ . The Higgs boson total decay width is ${\mathrm{\Gamma }}_H={3.9}_{-2.2}^{+2.7}\mathrm{MeV}$ , in agreement with the standard model prediction. The uncertainty in this result represents a factor of 3 improvement over the previous CMS result in this decay channel. 

   more » « less
4. Search for a Neutral Gauge Boson with Nonuniversal Fermion Couplings in Vector Boson Fusion Processes in Proton-Proton Collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/srvm-f1h3  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Benato, L; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; et al (August 2025, Physical Review Letters)

   The first search for a heavy neutral spin-1 gauge boson ( $Z^{\prime }$ ) with nonuniversal fermion couplings produced via vector boson fusion processes and decaying to tau leptons or $W$ bosons is presented. The analysis is performed using LHC data at $\sqrt{s}=13\mathrm{TeV}$ , collected from 2016 to 2018 with the CMS experiment and corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ . The data are consistent with the standard model predictions. Upper limits are set on the product of the cross section for production of the $Z^{\prime }$ boson and its branching fraction to $\tau \tau$ or $WW$ . The presence of a $Z^{\prime }$ boson decaying to ${\tau }^{+}{\tau }^{-}$ ( $W^{+}{W}^{-}$ ) is excluded for masses up to 2.45(1.60) TeV, depending on the $Z^{\prime }$ boson coupling to standard model weak bosons, and assuming a $Z^{\prime }\to {\tau }^{+}{\tau }^{-}$ ( $W^{+}{W}^{-}$ ) branching fraction of 50%. 

   more » « less
5. Search for Narrow Trijet Resonances in Proton-Proton Collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevLett.133.011801  

   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 (July 2024, Physical Review Letters)

   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 $138{\mathrm{fb}}^{-1}$ at $\sqrt{s}=13\mathrm{TeV}$ , collected at the CERN LHC. No significant deviations from the background predictions are observed between 1.75 and 9.00 TeV. The results provide the first mass limits on a right-handed boson $Z_R$ 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. © 2024 CERN, for the CMS Collaboration2024CERN 

   more » « less