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1. Modular apparatus for nuclear reactions spectroscopy (MARS): characterization and first application to determine $$^{12}$$C($$^6$$Li,$$^4$$He)$$^{14}\hbox {N}^{g.s}$$ nuclear reaction cross sections

   https://doi.org/10.1140/epjp/s13360-025-06305-0  

   Garrido-Gómez, L; Vegas-Díaz, A; Alvarez, M_A G; Fernández-García, J P; Fernández, B; Ferrer, F J; Lopez-Aires, D (May 2025, The European Physical Journal Plus)

   Abstract This work presents MARS (Modular apparatus for nuclear reactions spectroscopy) and its characterization prior to its first application to measure$$^6$$ $_{}^6$Li+$$^{12}$$ $_{}^{12}$C nuclear reactions. Measurements were performed at the 3 MV tandem accelerator of the CNA (National Accelerator Center), in Seville, Spain. The$$^{6}$$ $_{}^6$Li projectiles were accelerated at energies around the$$^6$$ $_{}^6$Li+$$^{12}$$ $_{}^{12}$C Coulomb barrier ($$V^{\text {cm}}_{B}\sim 3.0$$ $V_B^{\text{cm}}\sim 3.0$MeV - center of mass and$$V^{\text {lab}}_{B}\sim 4.5$$ $V_B^{\text{lab}}\sim 4.5$MeV - laboratory frame). Using a$$^{6}\hbox {Li}^{2+}$$ $_{}^6{\text{Li}}^{2+}$beam, we measured at 13 laboratory energies from 4.00 to 7.75 MeV. Thus, we present the excitation function of$$^{12}$$ $_{}^{12}$C($$^6$$ $_{}^6$Li,$$^4$$ $_{}^4$He)$$^{14}\hbox {N}^{g.s.}$$ $_{}^{14}{\text{N}}^{g.s.}$reaction, at 2 backward angles ($$110.0^\circ $$ $110.0^{\circ }$and$$140.0^\circ $$ $140.0^{\circ }$). The projectile dissociation, leading to this reaction, increases with the bombarding energies around the Coulomb barrier. This dissociation is favored at an optimum energy$$E_{b}^{\text {op}}$$ $E_b^{\text{op}}$$$\ge $$ $\ge$$$V_{B}$$ $V_B$+$$|Q_{bu}|$$ $|Q_{\mathrm{bu}}|$, where$$V_{B}$$ $V_B$is the Coulomb barrier of the system, and$$|Q_{bu}|$$ $|Q_{\mathrm{bu}}|$is the module ofQ-value for the$$^6$$ $_{}^6$Li dissociation into$$^4$$ $_{}^4$He+$$^2$$ $_{}^2$H. This result corroborates a systematic analysis of weakly bound projectiles reacting on several targets [1]. 

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2. 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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3. Semileptonic form factors for $$B\rightarrow D^*\ell \nu $$ at nonzero recoil from $$2+1$$-flavor lattice QCD: Fermilab Lattice and MILC Collaborations

   https://doi.org/10.1140/epjc/s10052-022-10984-9  

   Bazavov, A.; DeTar, C. E.; Du, D.; El-Khadra, A. X.; Gámiz, E.; Gelzer, Z.; Gottlieb, S.; Heller, U. M.; Kronfeld, A. S.; Laiho, J.; et al (December 2022, The European Physical Journal C)

   Abstract We present the first unquenched lattice-QCD calculation of the form factors for the decay$$B\rightarrow D^*\ell \nu $$ $B\to D^{\ast }\ell \nu$at nonzero recoil. Our analysis includes 15 MILC ensembles with$$N_f=2+1$$ $N_f=2+1$flavors of asqtad sea quarks, with a strange quark mass close to its physical mass. The lattice spacings range from$$a\approx 0.15$$ $a\approx 0.15$fm down to 0.045 fm, while the ratio between the light- and the strange-quark masses ranges from 0.05 to 0.4. The valencebandcquarks are treated using the Wilson-clover action with the Fermilab interpretation, whereas the light sector employs asqtad staggered fermions. We extrapolate our results to the physical point in the continuum limit using rooted staggered heavy-light meson chiral perturbation theory. Then we apply a model-independent parametrization to extend the form factors to the full kinematic range. With this parametrization we perform a joint lattice-QCD/experiment fit using several experimental datasets to determine the CKM matrix element$$|V_{cb}|$$ $|V_{\mathrm{cb}}|$. We obtain$$\left| V_{cb}\right| = (38.40 \pm 0.68_{\text {th}} \pm 0.34_{\text {exp}} \pm 0.18_{\text {EM}})\times 10^{-3}$$ $\left(V_{\mathrm{cb}}\right)=(38.40\pm 0.{68}_{\text{th}}\pm 0.{34}_{\text{exp}}\pm 0.{18}_{\text{EM}})\times {10}^{-3}$. The first error is theoretical, the second comes from experiment and the last one includes electromagnetic and electroweak uncertainties, with an overall$$\chi ^2\text {/dof} = 126/84$$ ${\chi }^2\text{/dof}=126/84$, which illustrates the tensions between the experimental data sets, and between theory and experiment. This result is in agreement with previous exclusive determinations, but the tension with the inclusive determination remains. Finally, we integrate the differential decay rate obtained solely from lattice data to predict$$R(D^*) = 0.265 \pm 0.013$$ $R\left(D^{\ast }\right)=0.265\pm 0.013$, which confirms the current tension between theory and experiment. 

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4. 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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5. Measurement of the mass dependence of the transverse momentum of lepton pairs in Drell–Yan production in proton–proton collisions at $$\sqrt{s} = 13\,\text {Te\hspace{-.08em}V} $$

   https://doi.org/10.1140/epjc/s10052-023-11631-7  

   Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Dragicevic, M.; Valle, A. Escalante; Frühwirth, R.; Jeitler, M.; Krammer, N.; et al (July 2023, The European Physical Journal C)

   Abstract The double differential cross sections of the Drell–Yan lepton pair ($$\ell ^+\ell ^-$$ ${\ell }^{+}{\ell }^{-}$, dielectron or dimuon) production are measured as functions of the invariant mass$$m_{\ell \ell }$$ $m_{\ell \ell }$, transverse momentum$$p_{\textrm{T}} (\ell \ell )$$ $p_{\text{T}}\left(\ell \ell \right)$, and$$\varphi ^{*}_{\eta }$$ ${\phi }_{\eta }^{\ast }$. The$$\varphi ^{*}_{\eta }$$ ${\phi }_{\eta }^{\ast }$observable, derived from angular measurements of the leptons and highly correlated with$$p_{\textrm{T}} (\ell \ell )$$ $p_{\text{T}}\left(\ell \ell \right)$, is used to probe the low-$$p_{\textrm{T}} (\ell \ell )$$ $p_{\text{T}}\left(\ell \ell \right)$region in a complementary way. Dilepton masses up to 1$$\,\text {Te\hspace{-.08em}V}$$ $\text{Te}\text{V}$are investigated. Additionally, a measurement is performed requiring at least one jet in the final state. To benefit from partial cancellation of the systematic uncertainty, the ratios of the differential cross sections for various$$m_{\ell \ell }$$ $m_{\ell \ell }$ranges to those in the Z mass peak interval are presented. The collected data correspond to an integrated luminosity of 36.3$$\,\text {fb}^{-1}$$ ${\text{fb}}^{-1}$of proton–proton collisions recorded with the CMS detector at the LHC at a centre-of-mass energy of 13$$\,\text {Te\hspace{-.08em}V}$$ $\text{Te}\text{V}$. Measurements are compared with predictions based on perturbative quantum chromodynamics, including soft-gluon resummation. 

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