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1. Dark Matter Axion Search with HAYSTAC Phase II

   https://doi.org/10.1103/PhysRevLett.134.151006  

   Bai, Xiran; Jewell, M J; Echevers, J; van_Bibber, K; Droster, A; Esmat, Maryam H; Ghosh, Sumita; Graham, Eleanor; Jackson, H; Laffan, Claire; et al (April 2025, Physical Review Letters)

   This Letter reports new results from the HAYSTAC experiment’s search for dark matter axions in our galactic halo. It represents the widest search to date that utilizes squeezing to realize subquantum limited noise. The new results cover $1.71\mathrm{\mu }\mathrm{eV}$of newly scanned parameter space in the mass ranges $17.28–18.44\mathrm{\mu }\mathrm{eV}$and $18.71–19.46\mathrm{\mu }\mathrm{eV}$. No statistically significant evidence of an axion signal was observed, excluding couplings $\left|g_{\gamma }\right|\ge 2.75\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$and $\left|g_{\gamma }\right|\ge 2.96\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$at the 90% confidence level over the respective region. By combining this data with previously published results using HAYSTAC’s squeezed state receiver, a total of $2.27\mathrm{\mu }\mathrm{eV}$of parameter space has now been scanned between $16.96–19.46\mathrm{\mu }\mathrm{eV}$ $\mu \mathrm{eV}$, excluding $\left|g_{\gamma }\right|\ge 2.86\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$at the 90% confidence level. These results demonstrate the squeezed state receiver’s ability to probe axion models over a significant mass range while achieving a scan rate enhancement relative to a quantum-limited experiment. Published by the American Physical Society2025 

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2. First Measurement of $R\left(X_{\tau /\ell }\right)$ as an Inclusive Test of the $b\to c\tau \nu$ Anomaly

   https://doi.org/10.1103/PhysRevLett.132.211804  

   Adachi, I; Adamczyk, K; Aggarwal, L; Ahmed, H; Aihara, H; Akopov, N; Aloisio, A; Asner, D M; Atmacan, H; Aushev, T; et al (May 2024, Physical Review Letters)

   We measure the tau-to-light-lepton ratio of inclusive $B$-meson branching fractions $R\left(X_{\tau /\ell }\right)\equiv \mathcal{B}(B\to X\tau \nu )/\mathcal{B}(B\to X\ell \nu )$, where $\ell$indicates an electron or muon, and thereby test the universality of charged-current weak interactions. We select events that have one fully reconstructed $B$meson and a charged lepton candidate from $189{\mathrm{fb}}^{-1}$of electron-positron collision data collected with the Belle II detector. We find $R\left(X_{\tau /\ell }\right)=0.228\pm 0.016\left(\mathrm{stat}\right)\pm 0.036\left(\mathrm{syst}\right)$, in agreement with standard-model expectations. This is the first direct measurement of $R\left(X_{\tau /\ell }\right)$. Published by the American Physical Society2024 

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3. First Determination of the Spin-Parity of ${\mathrm{\Xi }}_c(3055{)}^{+,0}$ Baryons

   https://doi.org/10.1103/PhysRevLett.134.081901  

   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 (February 2025, Physical Review Letters)

   The ${\mathrm{\Xi }}_b^{0(-)}\to {\mathrm{\Xi }}_c\left(3055{)}^{+\left(0\right)}\right(\to D^{+\left(0\right)}\mathrm{\Lambda }){\pi }^{-}$decay chains are observed, and the spin-parity of ${\mathrm{\Xi }}_c(3055{)}^{+\left(0\right)}$baryons is determined for the first time. The measurement is performed using proton-proton collision data at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$, recorded by the LHCb experiment between 2016 and 2018. The spin-parity of the ${\mathrm{\Xi }}_c(3055{)}^{+\left(0\right)}$baryons is determined to be $3/2^{+}$with a significance of more than $6.5\sigma$( $3.5\sigma$) compared to all other tested hypotheses. The up-down asymmetries of the ${\mathrm{\Xi }}_b^{0(-)}\to {\mathrm{\Xi }}_c(3055{)}^{+\left(0\right)}{\pi }^{-}$transitions are measured to be $-0.92\pm 0.10\pm 0.05$( $-0.92\pm 0.16\pm 0.22$), consistent with maximal parity violation, where the first uncertainty is statistical and the second is systematic. These results support the hypothesis that the ${\mathrm{\Xi }}_c(3055{)}^{+\left(0\right)}$baryons correspond to the first $D$-wave $\lambda$-mode excitation of the ${\mathrm{\Xi }}_c$flavor triplet. © 2025 CERN, for the LHCb Collaboration2025CERN 

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4. Search for prompt production of pentaquarks in charm hadron final states

   https://doi.org/10.1103/PhysRevD.110.032001  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adeva, B; Adinolfi, M; Adlarson, P; Afsharnia, H; Agapopoulou, C; et al (August 2024, Physical Review D)

   A search for hidden-charm pentaquark states decaying to a range of ${\mathrm{\Sigma }}_c\overline{D}$and ${\mathrm{\Lambda }}_c^{+}\overline{D}$final states, as well as doubly charmed pentaquark states to ${\mathrm{\Sigma }}_{c}D$and ${\mathrm{\Lambda }}_c^{+}D$, is made using samples of proton-proton collision data corresponding to an integrated luminosity of $5.7{\mathrm{fb}}^{-1}$recorded by the LHCb detector at $\sqrt{s}=13\mathrm{TeV}$. Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of the ${\mathrm{\Lambda }}_c^{+}$baryon in the ${\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+}$decay mode. The known pentaquark states are also investigated, and their signal yields are found to be consistent with zero in all cases. © 2024 CERN, for the LHCb Collaboration2024CERN 

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5. Photoproduction of $K^{+}{K}^{-}$ Pairs in Ultraperipheral Collisions

   https://doi.org/10.1103/PhysRevLett.132.222303  

   Acharya, S; Adamová, D; Aglieri_Rinella, G; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; Akindinov, A; et al (May 2024, Physical Review Letters)

   $K^{+}{K}^{-}$pairs may be produced in photonuclear collisions, either from the decays of photoproduced $\varphi \left(1020\right)$mesons or directly as nonresonant $K^{+}{K}^{-}$pairs. Measurements of $K^{+}{K}^{-}$photoproduction probe the couplings between the $\varphi \left(1020\right)$and charged kaons with photons and nuclear targets. The kaon-proton scattering occurs at energies far above those available elsewhere. We present the first measurement of coherent photoproduction of $K^{+}{K}^{-}$pairs on lead ions in ultraperipheral collisions using the ALICE detector, including the first investigation of direct $K^{+}{K}^{-}$production. There is significant $K^{+}{K}^{-}$production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range $1.1<M_{KK}<1.4\mathrm{GeV}/c^2$above the $\varphi \left(1020\right)$resonance, for rapidity $\left|y_{KK}\right|<0.8$and $p_{T,KK}<0.1\mathrm{GeV}/c$, the measured coherent photoproduction cross section is $\mathrm{d}\sigma /\mathrm{d}y=3.37\pm 0.61\left(\text{stat}\right)\pm 0.15\left(\mathrm{syst}\right)\mathrm{mb}$. The center-of-mass energy per nucleon of the photon-nucleus (Pb) system $W_{\gamma \mathrm{Pb},n}$ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for $\varphi \left(1020\right)$photoproduction alone. The mass spectrum is fit to a cocktail consisting of $\varphi \left(1020\right)$decays, direct $K^{+}{K}^{-}$photoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for direct $K^{+}{K}^{-}$photoproduction are presented. © 2024 CERN, for the ALICE Collaboration2024CERN 

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