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1. Search for exotic decays of the Higgs boson to a pair of pseudoscalars in the $$\upmu \upmu \text{ b } \text{ b } $$ and $$\uptau \uptau \text{ b } \text{ b } $$ final states

   https://doi.org/10.1140/epjc/s10052-024-12727-4  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Del_Valle, A Escalante; Hussain, P S; et al (May 2024, The European Physical Journal C)

   Abstract A search for exotic decays of the Higgs boson ($$\text {H}$$ $\text{H}$) with a mass of 125$$\,\text {Ge}\hspace{-.08em}\text {V}$$ $\text{Ge}\text{V}$to a pair of light pseudoscalars$$\text {a}_{1} $$ ${\text{a}}_1$is performed in final states where one pseudoscalar decays to two$${\textrm{b}}$$ $\text{b}$quarks and the other to a pair of muons or$$\tau $$ $\tau$leptons. A data sample of proton–proton collisions at$$\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V} $$ $\sqrt{s}=13\text{Te}\text{V}$corresponding to an integrated luminosity of 138$$\,\text {fb}^{-1}$$ ${\text{fb}}^{-1}$recorded with the CMS detector is analyzed. No statistically significant excess is observed over the standard model backgrounds. Upper limits are set at 95% confidence level ($$\text {CL}$$ $\text{CL}$) on the Higgs boson branching fraction to$$\upmu \upmu \text{ b } \text{ b } $$ $\mu \mu \text{b}\text{b}$and to$$\uptau \uptau \text{ b } \text{ b },$$ $\tau \tau \text{b}\text{b},$via a pair of$$\text {a}_{1} $$ ${\text{a}}_1$s. The limits depend on the pseudoscalar mass$$m_{\text {a}_{1}}$$ $m_{{\text{a}}_1}$and are observed to be in the range (0.17–3.3) $$\times 10^{-4}$$ $\times {10}^{-4}$and (1.7–7.7) $$\times 10^{-2}$$ $\times {10}^{-2}$in the$$\upmu \upmu \text{ b } \text{ b } $$ $\mu \mu \text{b}\text{b}$and$$\uptau \uptau \text{ b } \text{ b } $$ $\tau \tau \text{b}\text{b}$final states, respectively. In the framework of models with two Higgs doublets and a complex scalar singlet (2HDM+S), the results of the two final states are combined to determine upper limits on the branching fraction$${\mathcal {B}}(\text {H} \rightarrow \text {a}_{1} \text {a}_{1} \rightarrow \ell \ell \text{ b } \text{ b})$$ $B(\text{H}\to {\text{a}}_1{\text{a}}_1\to \ell \ell \text{b}\text{b})$at 95%$$\text {CL}$$ $\text{CL}$, with$$\ell $$ $\ell$being a muon or a$$\uptau $$ $\tau$lepton. For different types of 2HDM+S, upper bounds on the branching fraction$${\mathcal {B}}(\text {H} \rightarrow \text {a}_{1} \text {a}_{1} )$$ $B(\text{H}\to {\text{a}}_1{\text{a}}_1)$are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space,$${\mathcal {B}}(\text {H} \rightarrow \text {a}_{1} \text {a}_{1} )$$ $B(\text{H}\to {\text{a}}_1{\text{a}}_1)$values above 0.23 are excluded at 95%$$\text {CL}$$ $\text{CL}$for$$m_{\text {a}_{1}}$$ $m_{{\text{a}}_1}$values between 15 and 60$$\,\text {Ge}\hspace{-.08em}\text {V}$$ $\text{Ge}\text{V}$. 

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2. Highly-excited Rydberg excitons in synthetic thin-film cuprous oxide

   https://doi.org/10.1038/s41598-023-41465-y  

   DeLange, Jacob; Barua, Kinjol; Paul, Anindya Sundar; Ohadi, Hamid; Zwiller, Val; Steinhauer, Stephan; Alaeian, Hadiseh (December 2023, Scientific Reports)

   Abstract Cuprous oxide ($$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$) has recently emerged as a promising material in solid-state quantum technology, specifically for its excitonic Rydberg states characterized by large principal quantum numbers (n). The significant wavefunction size of these highly-excited states (proportional to$$n^2$$ $n^2$) enables strong long-range dipole-dipole (proportional to$$n^4$$ $n^4$) and van der Waals interactions (proportional to$$n^{11}$$ $n^{11}$). Currently, the highest-lying Rydberg states are found in naturally occurring$$\hbox {Cu}_2\hbox {O}$$ ${\text{Cu}}_2\text{O}$. However, for technological applications, the ability to grow high-quality synthetic samples is essential. The fabrication of thin-film$$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$samples is of particular interest as they hold potential for observing extreme single-photon nonlinearities through the Rydberg blockade. Nevertheless, due to the susceptibility of high-lying states to charged impurities, growing synthetic samples of sufficient quality poses a substantial challenge. This study successfully demonstrates the CMOS-compatible synthesis of a$$\hbox {Cu}{}_2\hbox {O}$$ $\text{Cu}{}_2\text{O}$thin film on a transparent substrate that showcases Rydberg excitons up to$$n = 8$$ $n=8$which is readily suitable for photonic device fabrications. These findings mark a significant advancement towards the realization of scalable and on-chip integrable Rydberg quantum technologies. 

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3. Measurement of multijet azimuthal correlations and determination of the strong coupling in proton-proton collisions at $$\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V} $$

   https://doi.org/10.1140/epjc/s10052-024-13116-7  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; Jeitler, M; et al (August 2024, The European Physical Journal C)

   Abstract A measurement is presented of a ratio observable that provides a measure of the azimuthal correlations among jets with large transverse momentum$$p_{\textrm{T}}$$ $p_{\text{T}}$. This observable is measured in multijet events over the range of$$p_{\textrm{T}} = 360$$ $p_{\text{T}}=360$–$$3170\,\text {Ge}\hspace{-.08em}\text {V} $$ $3170\text{Ge}\text{V}$based on data collected by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13$$\,\text {Te}\hspace{-.08em}\text {V}$$ $\text{Te}\text{V}$, corresponding to an integrated luminosity of 134$$\,\text {fb}^{-1}$$ ${\text{fb}}^{-1}$. The results are compared with predictions from Monte Carlo parton-shower event generator simulations, as well as with fixed-order perturbative quantum chromodynamics (pQCD) predictions at next-to-leading-order (NLO) accuracy obtained with different parton distribution functions (PDFs) and corrected for nonperturbative and electroweak effects. Data and theory agree within uncertainties. From the comparison of the measured observable with the pQCD prediction obtained with the NNPDF3.1 NLO PDFs, the strong coupling at the Z boson mass scale is$$\alpha _\textrm{S} (m_{{\textrm{Z}}}) =0.1177 \pm 0.0013\, \text {(exp)} _{-0.0073}^{+0.0116} \,\text {(theo)} = 0.1177_{-0.0074}^{+0.0117}$$ ${\alpha }_{\text{S}}\left(m_{\text{Z}}\right)=0.1177\pm 0.0013{\text{(exp)}}_{-0.0073}^{+0.0116}\text{(theo)}=0.{1177}_{-0.0074}^{+0.0117}$, where the total uncertainty is dominated by the scale dependence of the fixed-order predictions. A test of the running of$$\alpha _\textrm{S}$$ ${\alpha }_{\text{S}}$in the$$\,\text {Te}\hspace{-.08em}\text {V}$$ $\text{Te}\text{V}$region shows no deviation from the expected NLO pQCD behaviour. 

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4. Measurement of multidifferential cross sections for dijet production in proton–proton collisions at $$\sqrt{s} = 13\,\text {Te}\hspace{-.08em}\text {V} $$

   https://doi.org/10.1140/epjc/s10052-024-13606-8  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Valle, A_Escalante Del; Hussain, P S; et al (January 2025, The European Physical Journal C)

   Abstract A measurement of the dijet production cross section is reported based on proton–proton collision data collected in 2016 at$$\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V} $$ $\sqrt{s}=13\mathrm{Te}V$by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3$$\,\text {fb}^{-1}$$ ${\mathrm{fb}}^{-1}$. Jets are reconstructed with the anti-$$k_{\textrm{T}} $$ $k_{\text{T}}$algorithm for distance parameters of$$R=0.4$$ $R=0.4$and 0.8. Cross sections are measured double-differentially (2D) as a function of the largest absolute rapidity$$|y |_{\text {max}} $$ ${\left|y\right|}_{\max }$of the two jets with the highest transverse momenta$$p_{\textrm{T}}$$ $p_{\text{T}}$and their invariant mass$$m_{1,2} $$ $m_{1,2}$, and triple-differentially (3D) as a function of the rapidity separation$$y^{*} $$ $y^{\ast }$, the total boost$$y_{\text {b}} $$ $y_b$, and either$$m_{1,2} $$ $m_{1,2}$or the average$$p_{\textrm{T}}$$ $p_{\text{T}}$of the two jets. The cross sections are unfolded to correct for detector effects and are compared with fixed-order calculations derived at next-to-next-to-leading order in perturbative quantum chromodynamics. The impact of the measurements on the parton distribution functions and the strong coupling constant at the mass of the$${\text {Z}} $$ $Z$boson is investigated, yielding a value of$$\alpha _\textrm{S} (m_{{\text {Z}}}) =0.1179\pm 0.0019$$ ${\alpha }_{\text{S}}\left(m_Z\right)=0.1179\pm 0.0019$. 

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5. Measurements of $$\psi (2S)$$ and $$\chi _{c1}(3872)$$ production within fully reconstructed jets

   https://doi.org/10.1140/epjc/s10052-025-13852-4  

   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 (May 2025, The European Physical Journal C)

   Abstract This paper presents the first measurement of$$\psi {(2S)}$$ $\psi \left(2S\right)$and$$\chi _{c1}(3872)$$ ${\chi }_{c1}\left(3872\right)$meson production within fully reconstructed jets. Each quarkonium state (tag) is reconstructed via its decay to the$${{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} $$ $J/\psi$($$\rightarrow $$ $\to$$$\mu ^+\mu ^-$$ ${\mu }^{+}{\mu }^{-}$)$$\pi ^+\pi ^-$$ ${\pi }^{+}{\pi }^{-}$final state in the forward region using proton-proton collision data collected by the LHCb experiment at the center-of-mass-energy of$$13\text {TeV} $$ $13\text{TeV}$in 2016, corresponding to an integrated luminosity of$$1.64\,\text {\,fb} ^{-1} $$ $1.64{\text{,fb}}^{-1}$. The fragmentation function, presented as the ratio of the quarkonium-tag transverse momentum to the full jet transverse momentum ($$p_{\textrm{T}} (\text {tag})/p_{\textrm{T}} (\text {jet})$$ $p_{\text{T}}\left(\text{tag}\right)/p_{\text{T}}\left(\text{jet}\right)$), is measured differentially in$$p_{\textrm{T}} (\text {jet})$$ $p_{\text{T}}\left(\text{jet}\right)$and$$p_{\textrm{T}} (\text {tag})$$ $p_{\text{T}}\left(\text{tag}\right)$bins. The distributions are separated into promptly produced quarkonia from proton-proton collisions and quarkonia produced from displacedb-hadron decays. While the displaced quarkonia fragmentation functions are in general well described by parton-shower predictions, the prompt quarkonium distributions differ significantly from fixed-order non-relativistic QCD (NRQCD) predictions followed by a QCD parton shower. 

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