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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2026). Characterization of nuclear breakup as a function of hard-scattering kinematics using dijets measured by ATLAS in p plus Pb collisions. Phys. Lett. B, 877, 140440–18pp.
Abstract: This Letter analyzes the sensitivity of event geometry estimators to the initial-state kinematics of hard scattering in proton-lead collisions. This analysis uses dijets as a proxy for the parton-parton scattering configuration, correlating it with event geometry estimators, namely the energy deposited in the Zero-Degree Calorimeter and the transverse energy recorded in the Forward Calorimeter in the Pb-going direction. The analysis uses data recorded by the ATLAS detector at the Large Hadron Collider with a nucleon-nucleon center-of-mass energy of 8.16 TeV, corresponding to an integrated luminosity of 56 nb(-1). The jets are measured within the pseudorapidity interval -2.8 < eta < 4.5, where positive eta values correspond to the direction of the proton beam. Results are presented as a function of the Bjorken-x of the parton originating from the proton, x(p). Both event geometry estimators are found to be dependent on x(p), with the energy deposited in the Zero-Degree Calorimeter about six times less sensitive to x(p) compared with the transverse energy deposited in the Forward Calorimeter.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2026). Search for the Higgs boson decay to a Z boson and a photon in pp collisions at √s=13 TeV and 13.6 TeV with the ATLAS detector. Phys. Lett. B, 876, 140313–21pp.
Abstract: A search for the Higgs boson decay to a.. boson and a photon in the ll gamma (l = e, mu) final state is performed using root s collisions at root s = 13.6 TeV recorded with the ATLAS detector at the Large Hadron Collider during 2022-2024, corresponding to an integrated luminosity of 165 fb(-1). The signal yield, normalised to the Standard Model prediction, is measured to be μ= 0.9(-0.6)(+0.7), compatible with the expected value of μ= 1.0 +/- 0.7. This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations under the background-only hypothesis. This result is combined with that of a similar search performed with 140 fb(-1) of root s = 13 TeV pp collisions to provide the best expected sensitivity to date to this rare decay, namely an observed (expected) signal strength of μ= 1.3(-0.5)(+0.6) (mu = 1.0(-0.5)(+0.6)), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model expectation.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2026). Study of Higgs boson pair production in the HH → b(b)over-barγγ final state with 308 fb-1 of data collected at √s=13 TeV and 13.6 TeV by the ATLAS experiment. Phys. Lett. B, 876, 140280–21pp.
Abstract: A search for Higgs boson pair production in the b (b) over bar gamma gamma final state is performed. The proton-proton collision dataset corresponds to an integrated luminosity of 308 fb-1, consisting of two samples, 140 fb(-1) at a centre-of-mass energy of root s = 13 TeV and 168 fb(-1) at root s = 13.6 TeV, recorded between 2015 and 2024 by the ATLAS detector at the CERN Large Hadron Collider. In addition to a larger dataset, this analysis improves upon the previous search in the same final state through several methodological and technical developments. The Higgs boson pair production cross section divided by the Standard Model prediction is found to be mu(HH) = 0.9(-1.1)(+1.4) (mu(HH) = 1(-1.0)(+1.3) expected), which translates into a 95% confidence-level upper limit of mu(HH) < 3.7. At the same confidence level the Higgs self-coupling modifier is constrained to be in the range -1.6 < kappa(lambda) < 6.6 (-1.8 < kappa(lambda) < 6.9 expected).
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Acevedo, A., Almudever, C. G., Garcia-March, M. A., Gomez-Lurbe, R., Ion, L., Lal Bera, M., et al. (2026). Adaptive time compressed QITE (ACQ) and its geometrical interpretation. Quantum Sci. Technol., 11(3), 035009–25pp.
Abstract: Imaginary time evolution (ITE) is a well-established method for ground-state preparation, a fundamental problem in many fields such as materials science, chemistry, and optimization. Quantum ITE (QITE) approximates this evolution on quantum hardware but suffers from high circuit depth and numerous measurements. In this work we introduce adaptive-time compressed QITE (ACQ), a novel algorithm that reduces resource-cost by combining adaptive time steps with circuit compression. This approach leverages geometric insights by characterizing its relationship to geodesic trajectories with a measure that distinguishes trajectories in CPN. Recalling that ITE is a gradient flow on the complex projective plane CPN, such trajectory measures allow one to measure the deviation from geodesicity of said flow. For Hamiltonians with only two distinct eigenvalues (spectral cardiality), ITE and QITE exactly trace geodesics, this fact motivates an adaptive strategy for systems whose corresponding spectral cardinality is greater than 2, where QITE unitaries are reused until an energy increase signals departure from the ITE path. This is implemented via a line search for energy minimization. Circuit compression is achieved by approximating the sequence of QITE unitaries with a single element of a one-parameter group. Numerical simulations on the transverse field Ising model and the Heisenberg model demonstrate that ACQ achieves comparable fidelity to standard QITE while significantly reducing the number of QITE optimizations and maintaining fixed circuit depth during propagation. Gate-count estimates and an analysis of the fidelity scaling with truncation parameters are provided. A gate count and performance comparison with the state of the art method double bracket QITE is also performed.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2026). Searches for B0 → K+ π- τ+τ- and Bs0 → K+K- τ+τ- Decays. Phys. Rev. Lett., 136(18), 181802–14pp.
Abstract: The first searches for B-0 -> K+ pi(-) tau(+)tau and B-s(0) -> K+ pi(-) tau(+)tau(-) decays at the LHCb experiment are conducted with pp collision data corresponding to an integrated luminosity of 5.4 fb(-1). The tau leptons are reconstructed using the tau(+) -> mu(+)(nu) over bar tau nu(mu) decay and the results are presented in bins of K+pi(-) or K+K- mass. No signal is observed and upper limits are set on the branching fractions. The searches result in the first upper limits for B-0 -> K+ pi(-) tau(+)tau(-) decays outside the K*(892)(0) region in K+pi(-) mass and the first limits for B-s(0) -> K+ pi(-) tau(+)tau(-) decays. The searches are recast into limits on the decays B-0 -> K*(892)(0)tau(+)tau(-) tand B-s(0) -> phi(1020)tau(+)tau(-) , yielding 2.8 x 10(-4) (2.5 x 10(-4)) and 4.7 x 10(-4) (4.1 x 10(-4)) at the 95% (90%) confidence level, respectively. For the decay BB0 -> K*(892)(0)tau(+)tau(-), this result improves on the current best upper limit by an order of magnitude.
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