More Like this

1. Search for $h_b\left(2P\right)\to \gamma {\chi }_{bJ}\left(1P\right)$ at $\sqrt{s}=10.860\mathrm{GeV}$

   https://doi.org/10.1103/PhysRevD.111.L011102  

   Boschetti, A; Mussa, R; Tamponi, U; Adachi, I; Aihara, H; Asner, D M; Aushev, T; Ayad, R; Banerjee, Sw; Belous, K; et al (January 2025, Physical Review D)

   In the bottomonium sector, the hindered magnetic dipole transitions between P-wave states $h_b\left(2P\right)\to {\chi }_{bJ}\left(1P\right)\gamma$ , $J=0$ , 1, 2, are expected to be severely suppressed according to the relativized quark model, due to the spin flip of the $b$ quark. Nevertheless, a recent model following the coupled-channel approach predicts the corresponding branching fractions to be enhanced by orders of magnitude. In this Letter, we report the first search for such transitions. We find no significant signals and set upper limits at 90% confidence level on the corresponding branching fractions: $\mathcal{B}\left[h_b\right(2P)\to \gamma {\chi }_{b0}(1P\left)\right]<2.7\times {10}^{-1}$ , $\mathcal{B}\left[h_b\right(2P)\to \gamma {\chi }_{b1}(1P\left)\right]<5.4\times {10}^{-3}$ and $\mathcal{B}\left[h_b\right(2P)\to \gamma {\chi }_{b2}(1P\left)\right]<1.3\times {10}^{-2}$ . These values help to constrain the parameters of the coupled-channel models. The results are obtained using a $121.4{\mathrm{fb}}^{-1}$ data sample taken around $\sqrt{s}=10.860\mathrm{GeV}$ with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. Published by the American Physical Society2025 

   more » « less
2. Observation of $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(2S\right)$ and search for $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(1S\right)$ , $\gamma X_b$ at $\sqrt{s}$ near 10.75 GeV

   https://doi.org/10.1103/9f61-rmvx  

   Adachi, I; Aggarwal, L; Ahmed, H; Ahn, Y; Aihara, H; Akopov, N; Alghamdi, S; Alhakami, M; Aloisio, A; Althubiti, N; et al (March 2026, Physical Review D)

   We present an analysis of the processes $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(1S\right)$ , $\eta \mathrm{\Upsilon }\left(2S\right)$ , and $\gamma X_b$ with $X_b\to {\pi }^{+}{\pi }^{-}{\chi }_{bJ},{\chi }_{bJ}\to \gamma \mathrm{\Upsilon }\left(1S\right)$ ( $J=1$ , 2) reconstructed from $\gamma \gamma {\pi }^{+}{\pi }^{-}{\ell }^{+}{\ell }^{-}$ $(\ell =e,\mu )$ final states in $19.6{\mathrm{fb}}^{-1}$ of Belle II data collected at four energy points near the peak of the $\mathrm{\Upsilon }\left(10753\right)$ resonance. Here, $X_b$ is a hypothetical bottomonium-sector partner of the $X\left(3872\right)$ . In the process $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(2S\right)$ , we observe a signal with a significance that exceeds $6.0\sigma$ when all energy points are combined. A signal with a significance of $4.2\sigma$ is observed at a center-of-mass energy of 10.653 GeV, close to the $B^{*}{\overline{B}}^{*}$ threshold. At this energy, we measure $\sigma \left(\eta \mathrm{\Upsilon }\right(2S\left)\right)/\sigma \left({\pi }^{+}{\pi }^{-}\mathrm{\Upsilon }\right(2S\left)\right)>23$ at the 90% confidence level, indicating a strong violation of heavy-quark spin symmetry. No significant signal is observed for $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(1S\right)$ or $\gamma X_b$ . Upper limits on the Born cross sections for the processes $e^{+}{e}^{-}\to \eta \mathrm{\Upsilon }\left(1S\right)$ and $e^{+}{e}^{-}\to \gamma X_b$ with $X_b\to {\pi }^{+}{\pi }^{-}{\chi }_{bJ}$ are determined. 

   more » « less
3. First measurement of $D_{s1}\left(1^{+}\right)(2536{)}^{+}$ and $D_{s2}^{*}\left(2^{+}\right)(2573{)}^{+}$ production in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ at the LHC

   https://doi.org/10.1103/PhysRevD.111.112005  

   Acharya, S; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; et al (June 2025, Physical Review D)

   The production yields of the orbitally excited charm-strange mesons ${\mathrm{D}}_{\mathrm{s}1}\left(1^{+}\right)(2536{)}^{+}$ and ${\mathrm{D}}_{\mathrm{s}2}^{*}\left(2^{+}\right)(2573{)}^{+}$ were measured for the first time in proton-proton (pp) collisions at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ with the ALICE experiment at the LHC. The ${\mathrm{D}}_{\mathrm{s}1}^{+}$ and ${\mathrm{D}}_{\mathrm{s}2}^{*+}$ mesons were measured at midrapidity ( $\left|y\right|<0.5$ ) in minimum-bias and high-multiplicity pp collisions in the transverse-momentum interval $2<p_{\mathrm{T}}<24\mathrm{GeV}/c$ . Their production yields relative to the ${\mathrm{D}}_{\mathrm{s}}^{+}$ ground-state yield were found to be compatible between minimum-bias and high-multiplicity collisions, as well as with previous measurements in ${\mathrm{e}}^{\pm }\mathrm{p}$ and ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ collisions. The measured ${\mathrm{D}}_{\mathrm{s}1}^{+}/{\mathrm{D}}_{\mathrm{s}}^{+}$ and ${\mathrm{D}}_{\mathrm{s}2}^{*+}/{\mathrm{D}}_{\mathrm{s}}^{+}$ yield ratios are described by statistical hadronization models and can be used to tune the parameters governing the production of excited charm-strange hadrons in Monte Carlo generators, such as 8. 

   more » « less
4. Search for charged lepton flavor violating $Z$ and $Z^{\prime }$ boson decays in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/8lw4-6lyk  

   Hayrapetyan, A; Makarenko, V; Tumasyan, A; Adam, W; Andrejkovic, J W; Benato, L; Bergauer, T; Dragicevic, M; Giordano, C; Hussain, P S; et al (December 2025, Physical Review D)

   A search for flavor violating decays of the $Z$ boson to charged leptons is performed using data from proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ collected with the CMS detector at the LHC, corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ . Each of the decays $Z\to e\mu$ , $Z\to e\tau$ , and $Z\to \mu \tau$ is considered. The data are consistent with the backgrounds expected from standard model processes. For the $Z\to e\mu$ channel the observed (expected) 95% confidence level upper limit on the branching fraction is $1.9\left(2.0\right)\times {10}^{-7}$ , which is the most stringent direct limit to date on this process; the corresponding limits for the $Z\to e\tau$ and $Z\to \mu \tau$ channels are $13.8\left(11.4\right)\times {10}^{-6}$ and $12.0\left(5.3\right)\times {10}^{-6}$ , respectively. Additionally, the $e\mu$ final state is used to search for lepton flavor violating decays of $Z^{\prime }$ resonances in the mass range from 110 to $500\mathrm{GeV}$ . No significant excess is observed above the predicted background levels. 

   more » « less
5. Energy Independence of the Collins Asymmetry in $p^{\uparrow }p$ Collisions

   https://doi.org/10.1103/jgsw-zhny  

   Aboona, B E; Adam, J; Adamczyk, L; Aggarwal, I; Aggarwal, M M; Ahammed, Z; Alshammri, A K; Aschenauer, E C; Aslam, S; Atchison, J; et al (December 2025, Physical Review Letters)

   The STAR experiment reports new, high-precision measurements of the transverse single-spin asymmetries for ${\pi }^{\pm }$ within jets, namely the Collins asymmetries, from transversely polarized $p^{\uparrow }p$ collisions at $\sqrt{s}=510\mathrm{GeV}$ . The energy-scaled distribution of jet transverse momentum, $x_{\mathrm{T}}=2p_{\mathrm{T},\text{jet}}/\sqrt{s}$ , shows a remarkable consistency for Collins asymmetries of ${\pi }^{\pm }$ in jets between $\sqrt{s}=200\mathrm{GeV}$ and 510 GeV. This indicates that the Collins asymmetries are nearly energy independent, with, at most, a very weak scale dependence in $p^{\uparrow }p$ collisions. These results extend to high-momentum scales ( $Q^2\le 3400{\mathrm{GeV}}^2$ ) and enable unique tests of evolution and universality in the transverse-momentum-dependent formalism, thus providing important constraints for the Collins fragmentation functions. 

   more » « less