More Like this

1. Search for $$ {\textrm{B}}_{\textrm{s}}^0 $$ → ℓ∓τ± with the semi-leptonic tagging method at Belle

   https://doi.org/10.1007/JHEP08(2023)178  

   Nayak, L ; Nishida, S ; Giri, A ; Adachi, I ; Aihara, H ; Asner, D M ; Atmacan, H ; Aulchenko, V ; Aushev, T ; Ayad, R ; et al ( August 2023 , Journal of High Energy Physics)

   We present a search for the lepton-flavor-violating decays$$ {B}_s^0 $$$B_s^0$→ℓ^∓τ^±, whereℓ=e, μ, using the full data sample of 121 fb⁻¹collected at the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energye⁺e⁻collider. We use$$ {B}_s^0{\overline{B}}_s^0 $$$B_s^0{\overline{B}}_s^0$events in which one$$ {B}_s^0 $$$B_s^0$meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for$$ {B}_s^0 $$$B_s^0$→ ℓ^∓τ^±decays and set upper limits on their branching fractions at 90% confidence level as$$ \mathcal{B} $$$B$($$ {B}_s^0 $$$B_s^0$→ e^∓τ^±)<14×10⁻⁴and$$ \mathcal{B} $$$B$($$ {B}_s^0 $$$B_s^0$→ μ^∓τ^±)<7.3×10⁻⁴. Our result represents the first upper limit on the$$ {B}_s^0 $$$B_s^0$→ e^∓τ^±decay rate.

    

   more » « less
2. A case study of SMEFT $$ \mathcal{O}\left(1/{\Lambda}^4\right) $$ effects in diboson processes: pp → W±(ℓ±ν)γ

   https://doi.org/10.1007/JHEP05(2024)223  

   Martin, Adam ( May 2024 , Journal of High Energy Physics)

   In this paper we explorepp→W^±(ℓ^±ν)γto$$ \mathcal{O}\left(1/{\Lambda}^4\right) $$$O\left(1/{\Lambda }^4\right)$in the SMEFT expansion. Calculations to this order are necessary to properly capture SMEFT contributions that grow with energy, as the interference between energy-enhanced SMEFT effects at$$ \mathcal{O}\left(1/{\Lambda}^2\right) $$$O\left(1/{\Lambda }^2\right)$and the Standard Model is suppressed. We find that there are several dimension eight operators that interfere with the Standard Model and lead to the same energy growth, ~$$ \mathcal{O}\left({E}^4/{\Lambda}^4\right) $$$O\left(E^4/{\Lambda }^4\right)$, as dimension six squared. While energy-enhanced SMEFT contributions are a main focus, our calculation includes the complete set of$$ \mathcal{O}\left(1/{\Lambda}^4\right) $$$O\left(1/{\Lambda }^4\right)$SMEFT effects consistent with U(3)⁵flavor symmetry. Additionally, we include the decay of theW^±→ ℓ^±ν, making the calculation actually$$ \overline{q}{q}^{\prime}\to {\ell}^{\pm}\nu \gamma $$$\overline{q}{q}^{\prime }\to {\ell }^{\pm }\mathrm{\nu \gamma }$. As such, we are able to study the impact of non-resonant SMEFT operators, such as$$ \left({L}^{\dagger }{\overline{\sigma}}^{\mu }{\tau}^IL\right)\left({Q}^{\dagger }{\overline{\sigma}}^{\nu }{\tau}^IQ\right) $$$\left(L^{†}{\overline{\sigma }}^{\mu }{\tau }^{I}L\right)\left(Q^{†}{\overline{\sigma }}^{\nu }{\tau }^{I}Q\right)$B_μν, which contribute to$$ \overline{q}{q}^{\prime}\to {\ell}^{\pm}\nu \gamma $$$\overline{q}{q}^{\prime }\to {\ell }^{\pm }\mathrm{\nu \gamma }$directly and not to$$ \overline{q}{q}^{\prime}\to {W}^{\pm}\gamma $$$\overline{q}{q}^{\prime }\to W^{\pm }\gamma$. We show several distributions to illustrate the shape differences of the different contributions.

    

   more » « less
3. Search for heavy resonances decaying into a Z or W boson and a Higgs boson in final states with leptons and b-jets in 139 fb−1 of pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

   https://doi.org/10.1007/JHEP06(2023)016  

   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 ( June 2023 , Journal of High Energy Physics)

   This article presents a search for new resonances decaying into aZorWboson and a 125 GeV Higgs bosonh, and it targets the$$ \nu \overline{\nu}b\overline{b} $$$\nu \overline{\nu }b\overline{b}$,$$ {\ell}^{+}{\ell}^{-}b\overline{b} $$${\ell }^{+}{\ell }^{-}b\overline{b}$, or$$ {\ell}^{\pm}\nu b\overline{b} $$${\ell }^{\pm }\mathrm{\nu b}\overline{b}$final states, whereℓ=eorμ, in proton-proton collisions at$$ \sqrt{s} $$$\sqrt{s}$= 13 TeV. The data used correspond to a total integrated luminosity of 139 fb⁻¹collected by the ATLAS detector during Run 2 of the LHC at CERN. The search is conducted by examining the reconstructed invariant or transverse mass distributions ofZhorWhcandidates for evidence of a localised excess in the mass range from 220 GeV to 5 TeV. No significant excess is observed and 95% confidence-level upper limits between 1.3 pb and 0.3 fb are placed on the production cross section times branching fraction of neutral and charged spin-1 resonances and CP-odd scalar bosons. These limits are converted into constraints on the parameter space of the Heavy Vector Triplet model and the two-Higgs-doublet model.

    

   more » « less
4. 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)

   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}$.

    

   more » « less
5. Measurement of the e+e− → $$ {B}_s^0{\overline{B}}_s^0X $$ cross section in the energy range from 10.63 to 11.02 GeV using inclusive $$ {D}_s^{+} $$ and D0 production

   https://doi.org/10.1007/JHEP08(2023)131  

   Zhukova, V ; Mizuk, R ; Adachi, I ; Aihara, H ; Al_Said, S ; Asner, D M ; Atmacan, H ; Aulchenko, V ; Aushev, T ; Ayad, R ; et al ( August 2023 , Journal of High Energy Physics)

   We report the first measurement of the inclusivee⁺e⁻→$$ b\overline{b} $$$b\overline{b}$→$$ {D}_s^{\pm } $$$D_s^{\pm }$Xande⁺e⁻→$$ b\overline{b} $$$b\overline{b}$→ D⁰/$$ {\overline{D}}^0 $$${\overline{D}}^0$Xcross sections in the energy range from 10.63 to 11.02 GeV. Based on these results, we determineσ(e⁺e⁻→$$ {B}_s^0{\overline{B}}_s^0 $$$B_s^0{\overline{B}}_s^0$X) andσ(e⁺e⁻→$$ B\overline{B} $$$B\overline{B}$X) in the same energy range. We measure the fraction of$$ {B}_s^0 $$$B_s^0$events at Υ(10860) to bef_s= ($$ {22.0}_{-2.1}^{+2.0} $$${22.0}_{-2.1}^{+2.0}$)%. We determine also the ratio of the$$ {B}_s^0 $$$B_s^0$inclusive branching fractions$$ \mathcal{B} $$$B$($$ {B}_s^0 $$$B_s^0$→ D⁰/$$ {\overline{D}}^0 $$${\overline{D}}^0$X)/$$ \mathcal{B} $$$B$($$ {B}_s^0 $$$B_s^0$→$$ {D}_s^{\pm } $$$D_s^{\pm }$X) = 0.416 ± 0.018 ± 0.092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energye⁺e⁻collider.

    

   more » « less