More Like this

1. Simultaneous Probe of the Charm and Bottom Quark Yukawa Couplings Using $t\overline{t}H$ Events

   https://doi.org/10.1103/9nwb-splk  

   Hayrapetyan, A; Makarenko, V; Tumasyan, A; Adam, W; Andrejkovic, J W; Benato, L; Bergauer, T; Dragicevic, M; Giordano, C; Hussain, P S; et al (January 2026, Physical Review Letters)

   A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, $H\to c\overline{c}$ , produced in association with a top quark-antiquark pair ( $t\overline{t}H$ ) is presented. The search is performed with data from proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ , corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ . Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed $t\overline{t}H\left(H\to b\overline{b}\right)$ event rate relative to the standard model expectation is ${0.91}_{-0.22}^{+0.26}$ . The observed (expected) upper limit on the product of production cross section and branching fraction $\sigma \left(t\overline{t}H\right)\mathcal{B}(H\to c\overline{c})$ is 0.11 (0.13) pb at 95% confidence level, corresponding to 7.8 (8.7) times the standard model prediction. When combined with the previous search for $H\to c\overline{c}$ via associated production with a $W$ or $Z$ boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, ${\kappa }_c$ , is $\left|{\kappa }_c\right|<3.5$ (2.7), the most stringent constraint to date. 

   more » « less
2. Search for bottom-type vectorlike quark pair production in dileptonic and fully hadronic final states in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevD.110.052004  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; Jeitler, M; et al (September 2024, Physical Review D)

   A search is described for the production of a pair of bottom-type vectorlike quarks ( $B$ VLQs) with mass greater than 1000 GeV. Each $B$ VLQ decays into a $b$ quark and a Higgs boson, a $b$ quark and a $Z$ boson, or a $t$ quark and a $W$ boson. This analysis considers both fully hadronic final states and those containing a charged lepton pair from a $Z$ boson decay. The products of the $H\to bb$ boson decay and of the hadronic $Z$ or $W$ boson decays can be resolved as two distinct jets or merged into a single jet, so the final states are classified by the number of reconstructed jets. The analysis uses data corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ collected in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ with the CMS detector at the LHC from 2016 to 2018. No excess over the expected background is observed. Lower limits are set on the $B$ VLQ mass at the 95% confidence level. These depend on the $B$ VLQ branching fractions and are 1570 and 1540 GeV for 100% $B\to bH$ and 100% $B\to bZ$ , respectively. In most cases, the mass limits obtained exceed previous limits by at least 100 GeV. © 2024 CERN, for the CMS Collaboration2024CERN 

   more » « less
3. Search for charged-lepton flavor violation in the production and decay of top quarks using trilepton final states in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevD.111.012009  

   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 (January 2025, Physical Review D)

   A search is performed for charged-lepton flavor violating processes in top quark ( $t$ ) production and decay. The data were collected by the CMS experiment from proton-proton collisions at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ . The selected events are required to contain one opposite-sign electron-muon pair, a third charged lepton (electron or muon), and at least one jet of which no more than one is associated with a bottom quark. Boosted decision trees are used to distinguish signal from background, exploiting differences in the kinematics of the final states particles. The data are consistent with the standard model expectation. Upper limits at 95% confidence level are placed in the context of effective field theory on the Wilson coefficients, which range between $0.024–0.424{\mathrm{TeV}}^{-2}$ depending on the flavor of the associated light quark and the Lorentz structure of the interaction. These limits are converted to upper limits on branching fractions involving up (charm) quarks, $t\to e\mu u$ ( $t\to e\mu c$ ), of $0.032\left(0.498\right)\times {10}^{-6}$ , $0.022\left(0.369\right)\times {10}^{-6}$ , and $0.012\left(0.216\right)\times {10}^{-6}$ for tensorlike, vectorlike, and scalarlike interactions, respectively. 

   more » « less
4. Search for $\gamma H$ production and constraints on the Yukawa couplings of light quarks to the Higgs boson

   https://doi.org/10.1103/6s8n-pvmy  

   Chekhovsky, V; Hayrapetyan, A; Makarenko, V; Tumasyan, A; Adam, W; Andrejkovic, J W; Benato, L; Bergauer, T; Chatterjee, S; Damanakis, K; et al (December 2025, Physical Review D)

   A search for $\gamma H$ production is performed with data from the CMS experiment at the LHC corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ at a proton-proton center-of-mass collision energy of $13\mathrm{TeV}$ . The analysis focuses on the topology of a boosted Higgs boson recoiling against a high-energy photon. The final states of $H\to b\overline{b}$ and $H\to 4\ell$ are analyzed. This study examines effective $HZ\gamma$ and $H\gamma \gamma$ anomalous couplings within the context of an effective field theory. In this approach, the production cross section is constrained to be ${\sigma }_{\gamma H}<16.4\mathrm{fb}$ at 95% confidence level (CL). Simultaneous constraints on four anomalous couplings involving $HZ\gamma$ and $H\gamma \gamma$ are provided. Additionally, the production rate for $H\to 4\ell$ is examined to assess potential enhancements in the Yukawa couplings between light quarks and the Higgs boson. Assuming the standard model values for the Yukawa couplings of the bottom and top quarks, the following simultaneous constraints are obtained: ${\kappa }_u=(0.0\pm 1.5)\times {10}^3$ , ${\kappa }_d=\left({0.0}_{-6.8}^{+6.7}\right)\times {10}^2$ , ${\kappa }_s=0_{-32}^{+30}$ , and ${\kappa }_c={0.0}_{-2.8}^{+2.3}$ . This rules out the hypothesis that up- or down-type quarks in the first or second generation have the same Yukawa couplings as those in the third generation, with a CL greater than 95%. 

   more » « less
5. Measurement of the Top-Quark Production Cross Section and Charge Asymmetry at LHCb

   https://doi.org/10.1103/c1x7-f9wn  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (June 2026, Physical Review Letters)

   The first measurements of the top- and antitop-quark differential production cross sections and the top-quark charge asymmetry in the forward region are presented, using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ . The total production cross sections of top and antitop quarks are also determined. Measurements are performed using the $\mu +b\text{-jet}$ final state within a fiducial region defined by $b$ -jet $p_{\mathrm{T},\text{jet}}>50\mathrm{GeV}$ and pseudorapidity $2.2<{\eta }_{\text{jet}}<4.0$ , with the muon from the $W$ -boson decay required to have $p_{\mathrm{T},\mu }>25\mathrm{GeV}$ and $2.0<{\eta }_{\mu }<4.5$ . The muon and $b$ -jet system must satisfy $p_{\mathrm{T}}(\mu +\text{jet})>20\mathrm{GeV}$ . The measured integrated production cross sections for the top and antitop quarks are ${\sigma }_t=0.95\pm 0.04\pm 0.08\pm 0.02\mathrm{pb}$ , ${\sigma }_{\overline{t}}=0.81\pm 0.03\pm 0.07\pm 0.02\mathrm{pb}$ , where the first uncertainty is statistical, the second systematic, and the third accounts for the luminosity uncertainty. The top-quark charge asymmetry is measured to be $A_C^t=0.08\pm 0.03\pm 0.01$ , where the first uncertainty is statistical and the second is systematic. These results are consistent with next-to-leading order Standard Model predictions. 

   more » « less