Determination of the strong coupling and its running from measurements of inclusive jet production

The value of the strong coupling S is determined in a comprehensive analysis at next-to-next-to-leading order accuracy in quantum chromodynamics. The analysis uses double-differential cross section measurements from the CMS Collaboration at the CERN LHC of inclusive jet production in proton-proton collisions at centre-of- mass energies of 2.76, 7, 8, and 13 TeV, combined with inclusive deep-inelastic data from HERA. The value $_S$($_Z$ ) = 0.1176 $^{+0.0014}_{-0.0016}$ is obtained at the scale of the Z boson mass. By using the measurements in different intervals of jet transverse momentum, the running of $_S$ is probed for energies between 100 and 1600 GeV

Observation of quantum entanglement in top quark pair production in proton–proton collisions at √s = 13 TeV

Entanglement is an intrinsic property of quantum mechanics and is predicted to be exhibited in the particles produced at the Large Hadron Collider. A measurement of the extent of entanglement in top quark-antiquark ( t t ̄ ) events produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed with the data recorded by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 36.3 fb−1. The events are selected based on the presence of two leptons with opposite charges and high transverse momentum. An entanglement-sensitive observable D is derived from the top quark spin-dependent parts of the t t ̄ production density matrix and measured in the region of the t t ̄ production threshold. Values of D < − 1 / 3 are evidence of entanglement and D is observed (expected) to be − 0.480 − 0.029 + 0.026 ( − 0.467 − 0.029 + 0.026 ) at the parton level. With an observed significance of 5.1 standard deviations with respect to the non-entangled hypothesis, this provides observation of quantum mechanical entanglement within t t ̄ pairs in this phase space. This measurement provides a new probe of quantum mechanics at the highest energies ever produced

Observation of γγ → ττ in proton-proton collisions and limits on the anomalous electromagnetic moments of the τ lepton

The production of a pair of τ leptons via photon–photon fusion, γγ → ττ, is observed for the f irst time in proton–proton collisions, with a significance of 5.3 standard deviations. This observation is based on a data set recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb−1. Events with a pair of τ leptons produced via photon–photon fusion are selected by requiring them to be back-to-back in the azimuthal direction and to have a minimum number of charged hadrons associated with their production vertex. The τ leptons are reconstructed in their leptonic and hadronic decay modes. The measured fiducial cross section of γγ → ττ is σfid obs = 12.4+3.8 −3.1 fb. Constraints are set on the contributions to the anomalous magnetic moment (aτ) and electric dipole moments (dτ) of the τ lepton originating from potential effects of new physics on the γττ vertex: aτ = 0.0009+0.0032 −0.0031 and |dτ| < 2.9×10−17ecm (95% confidence level), consistent with the standard model

Potraga za višestrukom produkcijom Higgsovih bozona u hadronskim konačnim stanjima na Velikom hadronskom sudarivaču

After the discovery of the Higgs boson, one of the main purposes of the physics program at the LHC has been a thorough characterization of its properties. Among important properties of Higgs lies trilinear and quartic Higgs self-coupling, accessible through di- Higgs and triple Higgs production respectively. This thesis primarily reports on two highly significant and intriguing studies that were performed utilizing data from the Run- 2(2016–2018) proton–proton collision at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC. The first study concerns the search for the non-resonant H pair produced through gluon-gluon fusion (ggF) and Vector Boson Fusion (VBF) modes in two photons and two b-jets final state. The b￣bγγ final state is one of the most sensitive channels to the HH signal thanks to a relatively clean signature of two high-energy photons and large branching ratio of two heavy-flavor high-energy jets (b-jets). A 95% confidence level (CL) upper limit on the product of Higgs boson pair production cross section and branching fraction are derived as a function of κλ parameter. The constraints on the anomalous coupling of a pair of H with a pair of gauge bosons was determined for the first time by the CMS collaboration. The second study focuses on the search for triple Higgs boson production in three b-jet pairs final state. Given the extremely low standard model (SM) cross-section for triple- Higgs production, the Two-Real Singlet Model (TRSM) is considered as an extension of SM. TRSM introduces two real scalars X and Y, which decay to three SM Higgs bosons which decays further to three pair of b-quarks through the process X → Y H → HHH → b￣bb￣bb￣ b. The search is performed in mass ranges of X (1–4 TeV) and Y (300–2800 GeV) where the H is highly Lorentz-boosted. In this kinematic regime, decayed b-quark pairs are collimated enough to allow the reconstruction of H using single large-area jets. We have considered two topologies: one topology where all three Higgs bosons are boosted and another where two of the three Higgs bosons are boosted. This analysis is still ongoing. A scan will be performed in a two dimensional plane spanned by the invariant mass of the two large-area jets associated to Y, and the invariant mass of three large-area jets used to reconstruct X.Rad ne sadrži sažetak na drugom jeziku

Potraga za višestrukom produkcijom Higgsovih bozona u hadronskim konačnim stanjima na Velikom hadronskom sudarivaču

After the discovery of the Higgs boson, one of the main purposes of the physics program at the LHC has been a thorough characterization of its properties. Among important properties of Higgs lies trilinear and quartic Higgs self-coupling, accessible through di- Higgs and triple Higgs production respectively. This thesis primarily reports on two highly significant and intriguing studies that were performed utilizing data from the Run- 2(2016–2018) proton–proton collision at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC. The first study concerns the search for the non-resonant H pair produced through gluon-gluon fusion (ggF) and Vector Boson Fusion (VBF) modes in two photons and two b-jets final state. The b￣bγγ final state is one of the most sensitive channels to the HH signal thanks to a relatively clean signature of two high-energy photons and large branching ratio of two heavy-flavor high-energy jets (b-jets). A 95% confidence level (CL) upper limit on the product of Higgs boson pair production cross section and branching fraction are derived as a function of κλ parameter. The constraints on the anomalous coupling of a pair of H with a pair of gauge bosons was determined for the first time by the CMS collaboration. The second study focuses on the search for triple Higgs boson production in three b-jet pairs final state. Given the extremely low standard model (SM) cross-section for triple- Higgs production, the Two-Real Singlet Model (TRSM) is considered as an extension of SM. TRSM introduces two real scalars X and Y, which decay to three SM Higgs bosons which decays further to three pair of b-quarks through the process X → Y H → HHH → b￣bb￣bb￣ b. The search is performed in mass ranges of X (1–4 TeV) and Y (300–2800 GeV) where the H is highly Lorentz-boosted. In this kinematic regime, decayed b-quark pairs are collimated enough to allow the reconstruction of H using single large-area jets. We have considered two topologies: one topology where all three Higgs bosons are boosted and another where two of the three Higgs bosons are boosted. This analysis is still ongoing. A scan will be performed in a two dimensional plane spanned by the invariant mass of the two large-area jets associated to Y, and the invariant mass of three large-area jets used to reconstruct X.Rad ne sadrži sažetak na drugom jeziku

Potraga za višestrukom produkcijom Higgsovih bozona u hadronskim konačnim stanjima na Velikom hadronskom sudarivaču

After the discovery of the Higgs boson, one of the main purposes of the physics program at the LHC has been a thorough characterization of its properties. Among important properties of Higgs lies trilinear and quartic Higgs self-coupling, accessible through di- Higgs and triple Higgs production respectively. This thesis primarily reports on two highly significant and intriguing studies that were performed utilizing data from the Run- 2(2016–2018) proton–proton collision at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC. The first study concerns the search for the non-resonant H pair produced through gluon-gluon fusion (ggF) and Vector Boson Fusion (VBF) modes in two photons and two b-jets final state. The b￣bγγ final state is one of the most sensitive channels to the HH signal thanks to a relatively clean signature of two high-energy photons and large branching ratio of two heavy-flavor high-energy jets (b-jets). A 95% confidence level (CL) upper limit on the product of Higgs boson pair production cross section and branching fraction are derived as a function of κλ parameter. The constraints on the anomalous coupling of a pair of H with a pair of gauge bosons was determined for the first time by the CMS collaboration. The second study focuses on the search for triple Higgs boson production in three b-jet pairs final state. Given the extremely low standard model (SM) cross-section for triple- Higgs production, the Two-Real Singlet Model (TRSM) is considered as an extension of SM. TRSM introduces two real scalars X and Y, which decay to three SM Higgs bosons which decays further to three pair of b-quarks through the process X → Y H → HHH → b￣bb￣bb￣ b. The search is performed in mass ranges of X (1–4 TeV) and Y (300–2800 GeV) where the H is highly Lorentz-boosted. In this kinematic regime, decayed b-quark pairs are collimated enough to allow the reconstruction of H using single large-area jets. We have considered two topologies: one topology where all three Higgs bosons are boosted and another where two of the three Higgs bosons are boosted. This analysis is still ongoing. A scan will be performed in a two dimensional plane spanned by the invariant mass of the two large-area jets associated to Y, and the invariant mass of three large-area jets used to reconstruct X.Rad ne sadrži sažetak na drugom jeziku

Lifetime, mixing and CPV measurements at ATLAS

Precision measurements of B-meson properties using proton--proton collision data collected by the ATLAS detector at the LHC are presented, probing fundamental parameters of B decay and mixing with sensitivity to physics beyond the Standard Model. The $B^0_d \to J/\psi K^{*0}$ effective lifetime is measured with record precision, $\tau = 1.5053 \pm 0.0012~\text{(stat.)} \pm 0.0035~\text{(syst.)}$~ps, from which the average decay width $\Gamma_d$ and the ratio $\Gamma_d / \Gamma_s = 0.9905 \pm 0.0022~\text{(stat.)} \pm 0.0036~\text{(syst.)} \pm 0.0057~\text{(ext.)}$ are derived, both in excellent agreement with Standard Model predictions. The most precise determination to date of the $B^0_d$ width difference, $\Delta\Gamma_d / \Gamma_d$, is also reported, together with a measurement of the CP-violating phase $\phi_s = -0.087 \pm 0.036~\text{(stat.)} \pm 0.021~\text{(syst.)}$~rad in $B^0_s \to J/\psi\phi$ decays, along with the width difference $\Delta\Gamma_s$ and angular observables. Simultaneous fits in mass, decay time, and angular variables exploit the excellent detector resolution to achieve world-leading sensitivity in B-physics measurements, thereby imposing stringent constraints on scenarios of new physics

Combination and interpretation of differential Higgs boson production cross sections in proton-proton collisions at s= \sqrt{s}= 13 TeV

Precision measurements of Higgs boson differential production cross sections are a key tool to probe the properties of the Higgs boson and test the standard model. New physics can affect both Higgs boson production and decay, leading to deviations from the distributions that are expected in the standard model. In this paper, combined measurements of differential spectra in a fiducial region matching the experimental selections are performed, based on analyses of four Higgs boson decay channels ($\gamma\gamma$, $\mathrm{Z}\mathrm{Z}^{(*)}$, $\mathrm{W}\mathrm{W}^{(*)}$, and $\tau\tau$) using proton-proton collision data recorded with the CMS detector at $\sqrt{s}=$ 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. The differential measurements are extrapolated to the full phase space and combined to provide the differential spectra. A measurement of the total Higgs boson production cross section is also performed using the $\gamma\gamma$ and ZZ decay channels, with a result of 53.4 $^{+2.9}_{-2.9}$ (stat) $^{+1.9}_{-1.8}$ (syst) pb, consistent with the standard model prediction of 55.6 $\pm$ 2.5 pb. The fiducial measurements are used to compute limits on Higgs boson couplings using the $\kappa$-framework and the SM effective field theory.Precision measurements of Higgs boson differential production cross sections are a key tool to probe the properties of the Higgs boson and test the standard model. New physics can affect both Higgs boson production and decay, leading to deviations from the distributions that are expected in the standard model. In this paper, combined measurements of differential spectra in a fiducial region matching the experimental selections are performed, based on analyses of four Higgs boson decay channels ($\gamma\gamma$, ZZ$^{(*)}$, WW$^{(*)}$, and $\tau\tau$) using proton-proton collision data recorded with the CMS detector at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. The differential measurements are extrapolated to the full phase space and combined to provide the differential spectra. A measurement of the total Higgs boson production cross section is also performed using the $\gamma\gamma$ and ZZ decay channels, with a result of 53.4$^{+2.9}_{-2.9}$ (stat)$^{+1.9}_{-1.8}$ (syst) pb, consistent with the standard model prediction of 55.6 $\pm$ 2.5 pb. The fiducial measurements are used to compute limits on Higgs boson couplings using the $\kappa$-framework and the SM effective field theory

Measurements of inclusive and differential Higgs boson production cross sections at s= \sqrt{s} = 13.6 TeV in the H→γγ \mathrm{H}\to\gamma\gamma decay channel

Inclusive and differential cross sections for Higgs boson production in proton-proton collisions at a centre-of-mass energy of 13.6 TeV are measured using data collected with the CMS detector at the LHC in 2022, corresponding to an integrated luminosity of 34.7 fb$^{-1}$. Events with the diphoton final state are selected, and the measured inclusive fiducial cross section is $\sigma_{\text{fid}}=$ 74 $\pm$ 11 (stat) $^{+5}_{-4}$ (syst) fb, in agreement with the standard model prediction of 67.8 $\pm$ 3.8 fb. Differential cross sections are measured as functions of several observables: the Higgs boson transverse momentum and rapidity, the number of associated jets, and the transverse momentum of the leading jet in the event. Within the uncertainties, the differential cross sections agree with the standard model predictions.Inclusive and differential cross sections for Higgs boson production in proton-proton collisions at a centre-of-mass energy of 13.6 TeV are measured using data collected with the CMS detector at the LHC in 2022, corresponding to an integrated luminosity of 34.7 fb$^{-1}$. Events with the diphoton final state are selected, and the measured inclusive fiducial cross section is $\sigma_\text{fid}$ = 74 $\pm$ 11 (stat) $^{+5}_{-4}$ (syst) fb, in agreement with the standard model prediction of 67.8 $\pm$ 3.8 fb. Differential cross sections are measured as functions of several observables: the Higgs boson transverse momentum and rapidity, the number of associated jets, and the transverse momentum of the leading jet in the event. Within the uncertainties, the differential cross sections agree with the standard model predictions

Search for the nonresonant and resonant production of a Higgs boson in association with an additional scalar boson in the γγττ \gamma\gamma\tau\tau final state in proton-proton collisions at s= \sqrt{s} = 13 TeV

The results of a search for the production of two scalar bosons in final states with two photons and two tau leptons are presented. The search considers both nonresonant production of a Higgs boson pair, HH, and resonant production via a new boson X which decays either to HH or to H and a new scalar Y. The analysis uses up to 138 fb$^{-1}$ of proton-proton collision data, recorded between 2016 and 2018 by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV. No evidence for signal is found in the data. For the nonresonant production, the observed (expected) upper limit at 95% confidence level (CL) on the HH production cross section is set at 930 (740) fb, corresponding to 33 (26) times the standard model prediction. At 95% CL, HH production is observed (expected) to be excluded for values of $\kappa_\lambda$ outside the range between-12 (-9.4) and 17 (15). Observed (expected) upper limits at 95% CL for the $\mathrm{X} \to \mathrm{H}\mathrm{H}$ cross section are found to be within 160 to 2200 (200 to 1800) fb, depending on the mass of X. In the $\mathrm{X} \to \mathrm{Y} (\tau\tau)\mathrm{H}(\gamma\gamma)$ search, the observed (expected) upper limits on the product of the production cross section and decay branching fractions vary between 0.059-1.2 fb (0.087-0.68 fb). For the $\mathrm{X} \to \mathrm{Y} (\gamma\gamma)\mathrm{H}(\tau\tau)$ search the observed (expected) upper limits on the product of the production cross section and $\mathrm{Y} \to \gamma\gamma$ branching fraction vary between 0.69-15 fb (0.73-8.3 fb) in the low Y mass search, tightening constraints on the next-to-minimal supersymmetric standard model, and between 0.64-10 fb (0.70-7.6 fb) in the high Y mass search.The results of a search for the production of two scalar bosons in final states with two photons and two tau leptons are presented. The search considers both nonresonant production of a Higgs boson pair, HH, and resonant production via a new boson X which decays either to HH or to H and a new scalar Y. The analysis uses up to 138 fb$^{-1}$ of proton-proton collision data, recorded between 2016 and 2018 by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV. No evidence for signal is found in the data. For the nonresonant production, the observed (expected) upper limit at 95% confidence level (CL) on the HH production cross section is set at 930 (740) fb, corresponding to 33 (26) times the standard model prediction. At 95% CL, HH production is observed (expected) to be excluded for values of $κ_λ$ outside the range between $-$12 ($-$9.4) and 17 (15). Observed (expected) upper limits at 95% CL for the XHH cross section are found to be within 160 to 2200 (200 to 1800) fb, depending on the mass of X. In the X $\to$ Y($γγ$)H($ττ$) search, the observed (expected) upper limits on the product of the production cross section and decay branching fractions vary between 0.059$-$1.2 fb (0.087$-$0.68 fb). For the X $\to$ Y($γγ$)H($ττ$) search the observed (expected) upper limits on the product of the production cross section and Y $to$ $γγ$ branching fraction vary between 0.69$-$15 fb (0.73$-$8.3 fb) in the low Y mass search, tightening constraints on the next-to-minimal supersymmetric standard model, and between 0.64$-$10 fb (0.70$-$7.6 fb) in the high Y mass search