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- 26 October 2026
- Published by Springer Nature in Journal of High Energy Physics
Search for CP violation in D+ → ϕπ+ decays
by R. Aaij, M. Abdelfatah, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, et al.
A bstract: A search for charge-parity ( CP ) violation in the Cabibbo-suppressed D ⁺ → ϕπ ⁺ decay is presented, using proton-proton collision data corresponding to an integrated luminosity of 6 fb ^{−
1} , collected at a centre-of-mass energy of 13 TeV with the LHCb detector during Run 2. An abundant sample of $$ {D}^{+}\to {K}_{\mathrm{S}}^0{\pi}^{+} $$ $D^{+} \to K_{S}^{0} π^{+}$ decays is employed to correct for asymmetries arising from the production of the charmed meson and from detection effects associated with the charged pion accompanying the ϕ meson. Asymmetries induced by interference of multiple processes, such as neutral kaon mixing, regeneration of neutral kaons, and interference between the Cabibbo-favoured $$ {D}^{+}\to {\overline{K}}^0{\pi}^{+} $$ $D^{+} \to {\bar{K}}^{0} π^{+}$ and the doubly Cabibbo-suppressed D ⁺ → K ⁰ π ⁺ decay, are subtracted. The direct CP asymmetry in the D ⁺ → ϕπ ⁺ decay is measured to be $$ {a}_{CP}\left({D}^{+}\to \phi {\pi}^{+}\right)=\left(0.1\pm 4.9\left(\mathrm{stat}\right)\pm 2.4\left(\mathrm{syst}\right)\right)\times {10}^{-4}. $$ $a_{CP} (D^{+} \to ϕ π^{+}) = (0.1 \pm 4.9 (stat) \pm 2.4 (syst)) \times 10^{- 4} .$ For the first time at a hadron collider, the modulus of the ratio and the relative strong phase of the D ⁺ → K ⁰ π ⁺ to $$ {D}^{+}\to {\overline{K}}^0{\pi}^{+} $$ $D^{+} \to {\bar{K}}^{0} π^{+}$ decay amplitudes are also investigated. Two-dimensional confidence intervals are reported for these parameters.
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- 26 October 2026
- Published by Springer Nature in Journal of High Energy Physics
Open Access
Search for CP violation in D+ → ϕπ+ decays
by R. Aaij, M. Abdelfatah, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, et al.
A bstract: A search for charge-parity ( CP ) violation in the Cabibbo-suppressed D ⁺ → ϕπ ⁺ decay is presented, using proton-proton collision data corresponding to an integrated luminosity of 6 fb ^{−
1} , collected at a centre-of-mass energy of 13 TeV with the LHCb detector during Run 2. An abundant sample of $$ {D}^{+}\to {K}_{\mathrm{S}}^0{\pi}^{+} $$ $D^{+} \to K_{S}^{0} π^{+}$ decays is employed to correct for asymmetries arising from the production of the charmed meson and from detection effects associated with the charged pion accompanying the ϕ meson. Asymmetries induced by interference of multiple processes, such as neutral kaon mixing, regeneration of neutral kaons, and interference between the Cabibbo-favoured $$ {D}^{+}\to {\overline{K}}^0{\pi}^{+} $$ $D^{+} \to {\bar{K}}^{0} π^{+}$ and the doubly Cabibbo-suppressed D ⁺ → K ⁰ π ⁺ decay, are subtracted. The direct CP asymmetry in the D ⁺ → ϕπ ⁺ decay is measured to be $$ {a}_{CP}\left({D}^{+}\to \phi {\pi}^{+}\right)=\left(0.1\pm 4.9\left(\mathrm{stat}\right)\pm 2.4\left(\mathrm{syst}\right)\right)\times {10}^{-4}. $$ $a_{CP} (D^{+} \to ϕ π^{+}) = (0.1 \pm 4.9 (stat) \pm 2.4 (syst)) \times 10^{- 4} .$ For the first time at a hadron collider, the modulus of the ratio and the relative strong phase of the D ⁺ → K ⁰ π ⁺ to $$ {D}^{+}\to {\overline{K}}^0{\pi}^{+} $$ $D^{+} \to {\bar{K}}^{0} π^{+}$ decay amplitudes are also investigated. Two-dimensional confidence intervals are reported for these parameters.
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- 26 October 2026
- Published by Springer Nature in The European Physical Journal C
Measurement of di-muons from 400 GeV/c protons interacting in a thick molybdenum/tungsten target
by A. Aksoy, R. Albanese, K. Albrecht, F. Alessio, A. Alexandrov, F. Aloschi, T. Arndt, D. Arutinov, A. Ballarino, L. Baudin, et al.
Di-muon events emanating from a replica of the SHiP target at the CERN SPS (with a 400 GeV/c proton beam) contain a clear signal of $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}}$$ $J / ψ$ production. The target consisted of 13 interaction lengths of molybdenum and tungsten, followed by a 2.4m iron hadron absorber. The di-muon rate is in reasonable agreement with Monte Carlo simulation based on Pythia v8. However, the $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}} $$ $J / ψ$ rate observed in the data is much lower than predicted by the Monte Carlo simulation, which is advantageous for SHiP since muons with a large $$p_\textrm{T} $$ $p_{T}$ are more difficult to deflect by the active muon shield. For the center of mass rapidity ( $$y_{\textrm{cm}} $$ $y_{cm}$ ) interval with the largest overlap with the NA50 measurement, $$0.3< y_{\textrm{cm}} < 0.6$$ $0.3 < y_{cm} < 0.6$ , we obtain the production cross-section per nucleon $$\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A$$ $σ (J / ψ) / A$ including the branching ratios of $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}} $$ $J / ψ$ decays into muons, $$B_{\mu ^+\mu ^-}$$ $B_{μ^{+} μ^{-}}$ : $$B_{\mu ^+\mu ^-}\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A=(1.18~\pm ~0.04~\pm ~0.10)~\textrm{nb}$$ $B_{μ^{+} μ^{-}} σ (J / ψ) / A = (1.18 \pm 0.04 \pm 0.10) nb$ /nucleon. This is to be compared to the NA50 extrapolated result (using a much thinner target): $$B_{\mu ^+\mu ^-}\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A=(0.99~\pm ~0.04)~\textrm{nb}$$ $B_{μ^{+} μ^{-}} σ (J / ψ) / A = (0.99 \pm 0.04) nb$ /nucleon. Within the systematic errors, no significant enhancement due to secondary production of $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}}$$ $J / ψ$ inside the target is observed. An upper limit at 90% confidence level of possible contributions from secondary collisions of $$<32\%$$ $< 32 %$ is obtained.
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- 26 October 2026
- Published by Springer Nature in The European Physical Journal C
Open Access
Measurement of di-muons from 400 GeV/c protons interacting in a thick molybdenum/tungsten target
by A. Aksoy, R. Albanese, K. Albrecht, F. Alessio, A. Alexandrov, F. Aloschi, T. Arndt, D. Arutinov, A. Ballarino, L. Baudin, et al.
Di-muon events emanating from a replica of the SHiP target at the CERN SPS (with a 400 GeV/c proton beam) contain a clear signal of $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}}$$ $J / ψ$ production. The target consisted of 13 interaction lengths of molybdenum and tungsten, followed by a 2.4m iron hadron absorber. The di-muon rate is in reasonable agreement with Monte Carlo simulation based on Pythia v8. However, the $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}} $$ $J / ψ$ rate observed in the data is much lower than predicted by the Monte Carlo simulation, which is advantageous for SHiP since muons with a large $$p_\textrm{T} $$ $p_{T}$ are more difficult to deflect by the active muon shield. For the center of mass rapidity ( $$y_{\textrm{cm}} $$ $y_{cm}$ ) interval with the largest overlap with the NA50 measurement, $$0.3< y_{\textrm{cm}} < 0.6$$ $0.3 < y_{cm} < 0.6$ , we obtain the production cross-section per nucleon $$\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A$$ $σ (J / ψ) / A$ including the branching ratios of $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}} $$ $J / ψ$ decays into muons, $$B_{\mu ^+\mu ^-}$$ $B_{μ^{+} μ^{-}}$ : $$B_{\mu ^+\mu ^-}\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A=(1.18~\pm ~0.04~\pm ~0.10)~\textrm{nb}$$ $B_{μ^{+} μ^{-}} σ (J / ψ) / A = (1.18 \pm 0.04 \pm 0.10) nb$ /nucleon. This is to be compared to the NA50 extrapolated result (using a much thinner target): $$B_{\mu ^+\mu ^-}\sigma ({J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}})/A=(0.99~\pm ~0.04)~\textrm{nb}$$ $B_{μ^{+} μ^{-}} σ (J / ψ) / A = (0.99 \pm 0.04) nb$ /nucleon. Within the systematic errors, no significant enhancement due to secondary production of $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi \hspace{1.111pt}}$$ $J / ψ$ inside the target is observed. An upper limit at 90% confidence level of possible contributions from secondary collisions of $$<32\%$$ $< 32 %$ is obtained.
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- 5 October 2026
- Published by Springer Nature in Journal of High Energy Physics
Evidence for the decay $ {B}_s^0\to {\phi \eta}^{\prime } $
by R. Aaij, M. Abdelfatah, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, et al.
A bstract: Using a dataset corresponding to an integrated luminosity of 9 fb ^{−
1} collected in proton-proton collisions between 2011 and 2018 by the LHCb experiment, evidence is found for the decay $$ {B}_s^0\to {\phi \eta}^{\prime } $$ $B_{s}^{0} \to {ϕη}^{'}$ with 3 . 5 σ significance. The branching ratio relative to the $$ {B}_s^0\to \phi \phi $$ $B_{s}^{0} \to ϕϕ$ decay is determined to be ℛ = (3 . 56 ± 0 . 79 ± 0 . 18 ± 0 . 06) × 10 ^{−
2} . This corresponds to a branching fraction, $$ \mathcal{B}\left({B}_s^0\to {\phi \eta}^{\prime}\right)=\left(0.66\pm 0.15\pm 0.03\pm 0.02\right)\times {10}^{-6} $$ $B (B_{s}^{0} \to {ϕη}^{'}) = (0.66 \pm 0.15 \pm 0.03 \pm 0.02) \times 10^{- 6}$ where, in both cases, the first uncertainty is statistical, the second systematic, and the third due to external branching fractions.
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- 5 October 2026
- Published by Springer Nature in Journal of High Energy Physics
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Evidence for the decay $ {B}_s^0\to {\phi \eta}^{\prime } $
by R. Aaij, M. Abdelfatah, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, et al.
A bstract: Using a dataset corresponding to an integrated luminosity of 9 fb ^{−
1} collected in proton-proton collisions between 2011 and 2018 by the LHCb experiment, evidence is found for the decay $$ {B}_s^0\to {\phi \eta}^{\prime } $$ $B_{s}^{0} \to {ϕη}^{'}$ with 3 . 5 σ significance. The branching ratio relative to the $$ {B}_s^0\to \phi \phi $$ $B_{s}^{0} \to ϕϕ$ decay is determined to be ℛ = (3 . 56 ± 0 . 79 ± 0 . 18 ± 0 . 06) × 10 ^{−
2} . This corresponds to a branching fraction, $$ \mathcal{B}\left({B}_s^0\to {\phi \eta}^{\prime}\right)=\left(0.66\pm 0.15\pm 0.03\pm 0.02\right)\times {10}^{-6} $$ $B (B_{s}^{0} \to {ϕη}^{'}) = (0.66 \pm 0.15 \pm 0.03 \pm 0.02) \times 10^{- 6}$ where, in both cases, the first uncertainty is statistical, the second systematic, and the third due to external branching fractions.
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- 4 September 2026
- Published by Springer Nature in Journal of High Energy Physics
Search for τ− → μ−μ+μ− decays at the LHCb experiment with Run 2 data
by R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, et al.
A bstract: A search for the lepton-flavour-violating decay τ ⁻ → μ ⁻ μ ⁺ μ ⁻ is carried out using data collected by the LHCb experiment between 2016 and 2018 in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb ^{−
1} . An upper limit of 1 . 9 (2 . 3) × 10 ^{−
8} is set at the 90% (95%) confidence level on the branching fraction of the decay.
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- 4 September 2026
- Published by Springer Nature in Journal of High Energy Physics
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Search for τ− → μ−μ+μ− decays at the LHCb experiment with Run 2 data
by R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, et al.
A bstract: A search for the lepton-flavour-violating decay τ ⁻ → μ ⁻ μ ⁺ μ ⁻ is carried out using data collected by the LHCb experiment between 2016 and 2018 in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb ^{−
1} . An upper limit of 1 . 9 (2 . 3) × 10 ^{−
8} is set at the 90% (95%) confidence level on the branching fraction of the decay.
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- 1 September 2026
- Published by Springer Nature in The European Physical Journal C
SND@LHC upgrade for the high-luminosity LHC: physics reach and installation scenarios
by Snd@Lhc Collaboration, D. Abbaneo, S. Ahmad, R. Albanese, A. Alexandrov, F. Alicante, F. Aloschi, K. Androsov, A. Anokhina, L. G. Arellano, et al.
The SND@LHC experiment is currently taking data at the Large Hadron Collider (LHC), exploring the unique forward region at pseudorapidities $$7.2<\eta <8.4$$ $7.2 < η < 8.4$ . Its physics programme covers neutrinos originating from heavy-flavour decays and feebly interacting particles produced in proton–proton collisions. Building upon the successful operation of the present detector, this paper presents the physics reach of the approved SND@LHC upgrade for Run 4 of the LHC, and compares it with an alternative installation scenario. Lowering the detector by approximately 40 cm and shifting it horizontally by about 30 cm, while keeping it off-axis, increases the total neutrino interaction rate by a factor of five. The paper describes the design of the upgraded detector and compares the physics performance in both installation scenarios.
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- 1 September 2026
- Published by Springer Nature in The European Physical Journal C
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SND@LHC upgrade for the high-luminosity LHC: physics reach and installation scenarios
by Snd@Lhc Collaboration, D. Abbaneo, S. Ahmad, R. Albanese, A. Alexandrov, F. Alicante, F. Aloschi, K. Androsov, A. Anokhina, L. G. Arellano, et al.
The SND@LHC experiment is currently taking data at the Large Hadron Collider (LHC), exploring the unique forward region at pseudorapidities $$7.2<\eta <8.4$$ $7.2 < η < 8.4$ . Its physics programme covers neutrinos originating from heavy-flavour decays and feebly interacting particles produced in proton–proton collisions. Building upon the successful operation of the present detector, this paper presents the physics reach of the approved SND@LHC upgrade for Run 4 of the LHC, and compares it with an alternative installation scenario. Lowering the detector by approximately 40 cm and shifting it horizontally by about 30 cm, while keeping it off-axis, increases the total neutrino interaction rate by a factor of five. The paper describes the design of the upgraded detector and compares the physics performance in both installation scenarios.
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- 1 September 2026
- Published by IOP Publishing in Journal of Instrumentation
Operation and performance of the Probe for Luminosity Measurement at LHCb
by F. Alessio, S. Barsuk, C. Beigbeder, A. Bellavista, O. Bezshyyko, I. Boiaryntseva, C. Bourgeois, A. Boyarintsev, M. Briere, L. Burmistrov, et al.
The Probe for LUminosity MEasurement (PLUME) detector is a dedicated luminosity monitor at the LHCb interaction point. It is a hodoscope comprising 48 Hamamatsu R760 photomultiplier tubes that detect Cherenkov light produced by particles travelling in the direction opposite to the LHCb spectrometer acceptance. PLUME provides real-time, bunch-by-bunch luminosity measurements during LHCb data taking and serves as the primary detector for controlling the luminosity levelling process at LHCb. In addition, its data are used offline, together with other dedicated counters from LHCb sub-systems, to determine the integrated luminosity delivered to the experiment. This paper reports on the detector's operational performance during the 2024–2026 data-taking period of Run 3. The integrated luminosity recorded by the LHCb experiment in pp collisions at √( s ) = 13.6 TeV during this period, as measured by the PLUME online luminosity counters for detector performance monitoring, amounts to ℒ = (26.71 ± 1.07) fb ^-1 . The luminosity values used in physics analyses are determined separately through dedicated offline calibrations based on van der Meer scans and Beam Gas Imaging techniques, and will be reported in a dedicated publication, as they are beyond the scope of this paper.
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- 1 September 2026
- Published by IOP Publishing in Journal of Instrumentation
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Operation and performance of the Probe for Luminosity Measurement at LHCb
by F. Alessio, S. Barsuk, C. Beigbeder, A. Bellavista, O. Bezshyyko, I. Boiaryntseva, C. Bourgeois, A. Boyarintsev, M. Briere, L. Burmistrov, et al.
The Probe for LUminosity MEasurement (PLUME) detector is a dedicated luminosity monitor at the LHCb interaction point. It is a hodoscope comprising 48 Hamamatsu R760 photomultiplier tubes that detect Cherenkov light produced by particles travelling in the direction opposite to the LHCb spectrometer acceptance. PLUME provides real-time, bunch-by-bunch luminosity measurements during LHCb data taking and serves as the primary detector for controlling the luminosity levelling process at LHCb. In addition, its data are used offline, together with other dedicated counters from LHCb sub-systems, to determine the integrated luminosity delivered to the experiment. This paper reports on the detector's operational performance during the 2024–2026 data-taking period of Run 3. The integrated luminosity recorded by the LHCb experiment in pp collisions at √( s ) = 13.6 TeV during this period, as measured by the PLUME online luminosity counters for detector performance monitoring, amounts to ℒ = (26.71 ± 1.07) fb ^-1 . The luminosity values used in physics analyses are determined separately through dedicated offline calibrations based on van der Meer scans and Beam Gas Imaging techniques, and will be reported in a dedicated publication, as they are beyond the scope of this paper.
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- 19 August 2026
- Published by Springer Nature in Journal of High Energy Physics
Measurement of the local and nonlocal amplitudes in B+ → K+μ+μ− decays
by R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, et al.
A bstract: This paper presents a thorough study of the local and nonlocal amplitudes in B ⁺ → K ⁺ μ ⁺ μ ⁻ transitions through an amplitude analysis of the dimuon mass spectrum of the decay. The analysis is based on pp collision data corresponding to an integrated luminosity of 8.4 fb ^{−
1} collected by the LHCb experiment during Run1 and Run2. This measurement employs a model that describes both one-particle and two-particle nonlocal amplitudes across the entirety of the dimuon mass spectrum, enabling the determination of both short- and long-distance contributions to the decay. The compatibility of the Wilson coefficient combinations $$ {C}_9+{C}_9^{\prime } $$ $C_{9} + C_{9}^{'}$ and $$ {C}_{10}+{C}_{10}^{\prime } $$ $C_{10} + C_{10}^{'}$ with the Standard Model prediction is found to vary between 1 . 6 σ and 4 σ , depending on the choice of local form factors.
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- 19 August 2026
- Published by Springer Nature in Journal of High Energy Physics
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Measurement of the local and nonlocal amplitudes in B+ → K+μ+μ− decays
by R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, et al.
A bstract: This paper presents a thorough study of the local and nonlocal amplitudes in B ⁺ → K ⁺ μ ⁺ μ ⁻ transitions through an amplitude analysis of the dimuon mass spectrum of the decay. The analysis is based on pp collision data corresponding to an integrated luminosity of 8.4 fb ^{−
1} collected by the LHCb experiment during Run1 and Run2. This measurement employs a model that describes both one-particle and two-particle nonlocal amplitudes across the entirety of the dimuon mass spectrum, enabling the determination of both short- and long-distance contributions to the decay. The compatibility of the Wilson coefficient combinations $$ {C}_9+{C}_9^{\prime } $$ $C_{9} + C_{9}^{'}$ and $$ {C}_{10}+{C}_{10}^{\prime } $$ $C_{10} + C_{10}^{'}$ with the Standard Model prediction is found to vary between 1 . 6 σ and 4 σ , depending on the choice of local form factors.
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- 19 August 2026
- Published by Springer Nature in The European Physical Journal C
Measurement of the muon flux at SND@LHC
by Snd@Lhc Collaboration, D. Abbaneo, S. Ahmad, R. Albanese, A. Alexandrov, F. Alicante, F. Aloschi, K. Androsov, A. Anokhina, L. G. Arellano, et al.
The SND@LHC experiment investigates neutrinos in the $$7.2< \eta < 8.4$$ $7.2 < η < 8.4$ forward pseudorapidity range. The detector consists of a veto system, a scintillating fiber tracker interleaved with emulsion cloud chambers, and a downstream muon system. Muons originating from collisions at ATLAS (IP1) constitute the primary background for CC neutrino interactions and determine the replacement frequency of the emulsion target. A precise characterization of this flux is therefore essential. In this work, we report the muon flux measured in the central $$31 \times 31$$ $31 \times 31$ $$\textrm{cm}^2$$ ${cm}^{2}$ fiducial area of the detector using data from 2023 through 2025. The measured fluxes for proton collisions are: (1.90±0.04) $$\times 10^{-2}$$ $\times 10^{- 2}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ (2023), (3.76 ± 0.09) $$\times $$ $\times$ $$\text {10}^{-2}$$ $10^{- 2}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ (2024), and (2.48 ± 0.05) $$\times 10^{-2}$$ $\times 10^{- 2}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ (2025). A 2024 reference proton run at $$\sqrt{s} = 5.36\text { TeV}$$ $\sqrt{s} = 5.36 TeV$ yielded (4.21 ± 0.14) $$\times $$ $\times$ $$\text {10}^{-2}$$ $10^{- 2}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ , providing a direct baseline for the heavy-ion energy regime. The measured fluxes for heavy-ion collisions are (3.11±0.12) $$\times \text {10}^{4}$$ $\times 10^{4}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ , (5.53±0.22) $$\times 10^{4}$$ $\times 10^{4}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ , and (3.24±0.13) $$\times \text {10}^{4}$$ $\times 10^{4}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ in 2023, 2024, and 2025, respectively. Uncertainties are dominated by systematic effects, with the statistical component contributing $$\lesssim $$ $≲$ 0.1% to the total uncertainty. These results are in agreement with Monte Carlo predictions.
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- 19 August 2026
- Published by Springer Nature in The European Physical Journal C
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Measurement of the muon flux at SND@LHC
by Snd@Lhc Collaboration, D. Abbaneo, S. Ahmad, R. Albanese, A. Alexandrov, F. Alicante, F. Aloschi, K. Androsov, A. Anokhina, L. G. Arellano, et al.
The SND@LHC experiment investigates neutrinos in the $$7.2< \eta < 8.4$$ $7.2 < η < 8.4$ forward pseudorapidity range. The detector consists of a veto system, a scintillating fiber tracker interleaved with emulsion cloud chambers, and a downstream muon system. Muons originating from collisions at ATLAS (IP1) constitute the primary background for CC neutrino interactions and determine the replacement frequency of the emulsion target. A precise characterization of this flux is therefore essential. In this work, we report the muon flux measured in the central $$31 \times 31$$ $31 \times 31$ $$\textrm{cm}^2$$ ${cm}^{2}$ fiducial area of the detector using data from 2023 through 2025. The measured fluxes for proton collisions are: (1.90±0.04) $$\times 10^{-2}$$ $\times 10^{- 2}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ (2023), (3.76 ± 0.09) $$\times $$ $\times$ $$\text {10}^{-2}$$ $10^{- 2}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ (2024), and (2.48 ± 0.05) $$\times 10^{-2}$$ $\times 10^{- 2}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ (2025). A 2024 reference proton run at $$\sqrt{s} = 5.36\text { TeV}$$ $\sqrt{s} = 5.36 TeV$ yielded (4.21 ± 0.14) $$\times $$ $\times$ $$\text {10}^{-2}$$ $10^{- 2}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ , providing a direct baseline for the heavy-ion energy regime. The measured fluxes for heavy-ion collisions are (3.11±0.12) $$\times \text {10}^{4}$$ $\times 10^{4}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ , (5.53±0.22) $$\times 10^{4}$$ $\times 10^{4}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ , and (3.24±0.13) $$\times \text {10}^{4}$$ $\times 10^{4}$ $$\text {nb/cm}^{2}$$ ${nb/cm}^{2}$ in 2023, 2024, and 2025, respectively. Uncertainties are dominated by systematic effects, with the statistical component contributing $$\lesssim $$ $≲$ 0.1% to the total uncertainty. These results are in agreement with Monte Carlo predictions.
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- 6 August 2026
- Published by Springer Nature in Journal of High Energy Physics
Measurement of CP asymmetries in $ {\overline{B}}^0\to {D}_s^{-}{D}^{+} $ and $ {\overline{B}}_s^0\to {D}_s^{-}{D}^{-} $ decays
by R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, et al.
A bstract: Measurements of the combined CP asymmetries in $$ {\overline{B}}^0\to {D}_s^{-}{D}^{+} $$ ${\bar{B}}^{0} \to D_{s}^{-} D^{+}$ and $$ {\overline{B}}_s^0\to {D}_s^{-}{D}^{-} $$ ${\bar{B}}_{s}^{0} \to D_{s}^{-} D^{-}$ decays are made using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb ^{−
1} . The measurements are found to be $$ {\displaystyle \begin{array}{l}{A}_{CP}\left({\overline{B}}^0\to {D}_s^{-}{D}^{+}\right)=0.0009\pm 0.0053\pm 0.0040,\\ {}{A}_{CP}\left({\overline{B}}_s^0\to {D}_s^{-}{D}^{-}\right)=0.103\pm 0.053\pm 0.010,\end{array}} $$ $\begin{matrix} A_{CP} ({\bar{B}}^{0} \to D_{s}^{-} D^{+}) = 0.0009 \pm 0.0053 \pm 0.0040, \\ A_{CP} ({\bar{B}}_{s}^{0} \to D_{s}^{-} D^{-}) = 0.103 \pm 0.053 \pm 0.010, \end{matrix}$ where the first and second uncertainties are statistical and systematic, respectively. This is the first measurement of this asymmetry in $$ {\overline{B}}_s^0 $$ ${\bar{B}}_{s}^{0}$ decays, and the most precise measurement to date for $$ {\overline{B}}^0 $$ ${\bar{B}}^{0}$ decays. Both measurements are found to be consistent with CP symmetry.
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- 6 August 2026
- Published by Springer Nature in Journal of High Energy Physics
Open Access
Measurement of CP asymmetries in $ {\overline{B}}^0\to {D}_s^{-}{D}^{+} $ and $ {\overline{B}}_s^0\to {D}_s^{-}{D}^{-} $ decays
by R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, et al.
A bstract: Measurements of the combined CP asymmetries in $$ {\overline{B}}^0\to {D}_s^{-}{D}^{+} $$ ${\bar{B}}^{0} \to D_{s}^{-} D^{+}$ and $$ {\overline{B}}_s^0\to {D}_s^{-}{D}^{-} $$ ${\bar{B}}_{s}^{0} \to D_{s}^{-} D^{-}$ decays are made using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb ^{−
1} . The measurements are found to be $$ {\displaystyle \begin{array}{l}{A}_{CP}\left({\overline{B}}^0\to {D}_s^{-}{D}^{+}\right)=0.0009\pm 0.0053\pm 0.0040,\\ {}{A}_{CP}\left({\overline{B}}_s^0\to {D}_s^{-}{D}^{-}\right)=0.103\pm 0.053\pm 0.010,\end{array}} $$ $\begin{matrix} A_{CP} ({\bar{B}}^{0} \to D_{s}^{-} D^{+}) = 0.0009 \pm 0.0053 \pm 0.0040, \\ A_{CP} ({\bar{B}}_{s}^{0} \to D_{s}^{-} D^{-}) = 0.103 \pm 0.053 \pm 0.010, \end{matrix}$ where the first and second uncertainties are statistical and systematic, respectively. This is the first measurement of this asymmetry in $$ {\overline{B}}_s^0 $$ ${\bar{B}}_{s}^{0}$ decays, and the most precise measurement to date for $$ {\overline{B}}^0 $$ ${\bar{B}}^{0}$ decays. Both measurements are found to be consistent with CP symmetry.
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- 5 August 2026
- Published by Springer Nature in Journal of High Energy Physics
Observation of the charmless purely baryonic decay $ {\Lambda}_b^0\to \Lambda p\overline{p} $
by R. Aaij, M. Abdelfatah, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, et al.
A bstract: A search for the charmless purely baryonic decay $$ {\Lambda}_b^0\to \Lambda p\overline{p} $$ $Λ_{b}^{0} \to Λ p \bar{p}$ is performed using proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of $$ \sqrt{s}=13 $$ $\sqrt{s} = 13$ TeV and corresponding to an integrated luminosity of 6 . 0 fb ^{−
1} . The signal decay is observed with a significance of 5.1 standard deviations. Its branching fraction is measured for the first time, relative to that of the topologically similar decay $$ {\Lambda}_b^0\to \Lambda {K}^{+}{K}^{-} $$ $Λ_{b}^{0} \to Λ K^{+} K^{-}$ . Contributions from intermediate charmonium resonances decaying to the $$ p\overline{p} $$ $p \bar{p}$ and K ⁺ K ⁻ final states are explicitly excluded with a requirement on the invariant mass of the companion hadron system, $$ m\left(h\overline{h}\right)<2.85 $$ $m (h \bar{h}) < 2.85$ GeV, where h stands for a proton or a charged kaon. The relative branching fraction is found to be $$ \frac{\mathcal{B}\left({\Lambda}_b^0\to \Lambda p\overline{p}\right)}{\mathcal{B}\left({\Lambda}_b^0\to \Lambda {K}^{+}{K}^{-}\right)}=\left(5.1\pm {1.3}_{\left(\mathrm{stat}\right)}\pm {0.3}_{\left(\mathrm{syst}\right)}\right)\times {10}^{-2}. $$ $\frac{B (Λ_{b}^{0} \to Λ p \bar{p})}{B (Λ_{b}^{0} \to Λ K^{+} K^{-})} = (5.1 \pm {1.3}_{(stat)} \pm {0.3}_{(syst)}) \times 10^{- 2} .$
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- 5 August 2026
- Published by Springer Nature in Journal of High Energy Physics
Open Access
Observation of the charmless purely baryonic decay $ {\Lambda}_b^0\to \Lambda p\overline{p} $
by R. Aaij, M. Abdelfatah, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, et al.
A bstract: A search for the charmless purely baryonic decay $$ {\Lambda}_b^0\to \Lambda p\overline{p} $$ $Λ_{b}^{0} \to Λ p \bar{p}$ is performed using proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of $$ \sqrt{s}=13 $$ $\sqrt{s} = 13$ TeV and corresponding to an integrated luminosity of 6 . 0 fb ^{−
1} . The signal decay is observed with a significance of 5.1 standard deviations. Its branching fraction is measured for the first time, relative to that of the topologically similar decay $$ {\Lambda}_b^0\to \Lambda {K}^{+}{K}^{-} $$ $Λ_{b}^{0} \to Λ K^{+} K^{-}$ . Contributions from intermediate charmonium resonances decaying to the $$ p\overline{p} $$ $p \bar{p}$ and K ⁺ K ⁻ final states are explicitly excluded with a requirement on the invariant mass of the companion hadron system, $$ m\left(h\overline{h}\right)<2.85 $$ $m (h \bar{h}) < 2.85$ GeV, where h stands for a proton or a charged kaon. The relative branching fraction is found to be $$ \frac{\mathcal{B}\left({\Lambda}_b^0\to \Lambda p\overline{p}\right)}{\mathcal{B}\left({\Lambda}_b^0\to \Lambda {K}^{+}{K}^{-}\right)}=\left(5.1\pm {1.3}_{\left(\mathrm{stat}\right)}\pm {0.3}_{\left(\mathrm{syst}\right)}\right)\times {10}^{-2}. $$ $\frac{B (Λ_{b}^{0} \to Λ p \bar{p})}{B (Λ_{b}^{0} \to Λ K^{+} K^{-})} = (5.1 \pm {1.3}_{(stat)} \pm {0.3}_{(syst)}) \times 10^{- 2} .$

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