Searcharxiv⌕ Search

arXiv subjects

G. Benane

Publications and source records attributed to G. Benane.

At least 19 recordsLinked to original sources
arXiv2026

Branching fraction measurements of $\eta$ and $\eta^\prime(958)$ anomalous decays

Branching fractions of $\eta$ and $\eta'(958)$ anomalous decays are measured using $pp$ collision data at a center-of-mass energy of $\sqrt{s}=13\,\text{TeV}$ collected by the LHCb experiment and corresponding to an integrated luminosity of $5.4\,\text{fb}^{-1}$. The measured values and upper limits are \begin{align*} \cal{B}(\eta\to\mu^+\mu^-) &= (5.02\pm0.14\pm0.18\pm0.26)\times10^{-6} , \\ \cal{B}(\eta'(958)\to\mu^+\mu^-) &<1.9\times10^{-7}\textrm{ at 90% CL} , \\ \cal{B}(\eta\to\pi^+\pi^-\mu^+\mu^-) &<5.4\times10^{-7}\textrm{ at 90% CL}, \\ \cal{B}(\eta'(958)\to\pi^+\pi^-\mu^+\mu^-) &= (2.73\pm0.14\pm0.13\pm0.14)\times10^{-5} , \end{align*} where the uncertainties are, respectively, statistical, systematic, and due to the external branching fraction of the $\phi(1020)\to\mu^+\mu^-$ decay, which is used for normalization. This marks the first experimental search for the $\eta'(958)$ decay, and the most precise measurement of the branching fraction $\cal{B}(\eta\to\mu^+\mu^-)$ to date.

hep-ex↗
arXiv2026

Amplitude analysis of $B^+ \!\to K^+ \pi^+ \pi^-$ decays

The branching fractions and quasi-two-body $C\!P$-violating asymmetries of intermediate states obtained through an amplitude analysis of the charmless three-body decay $B^+ \!\to K^+ \pi^+ \pi^-$ are reported. The analysis is based on $pp$ collision data at centre-of-mass energies $\sqrt{s}=7$ and $8\,\text{TeV}$ recorded with the LHCb detector, corresponding to an integrated luminosity of $3\,\text{fb}^{-1}$. The most challenging aspect of the amplitude modelling lies in the description of the dominant $K^+ \pi^-$ and $\pi^+ \pi^-$ S-wave contributions. This is achieved by three complementary approaches based on a physically motivated analytic model built on the isobar approximation, the K-matrix formalism, and a quasi-model-independent procedure in which overlapping crossing partial waves are simultaneously studied. In addition, alternative sets of results are presented, considering the $\pi^+ \pi^-$ final state to manifest either through direct $\omega(782)$ decays or $\rho(770)^0\textrm{-}\omega(782)$ mixing. The most precise measurements of branching fractions and $C\!P$ asymmetries are obtained for the vast majority of intermediate states, establishing firmer reference points against which to cleanly probe model-independent physics beyond the Standard Model. The results from all three approaches agree and provide new insight into strong dynamics and the origin of $C\!P$-violation effects in $B^+ \!\to K^+ \pi^+ \pi^-$ decays.

hep-ex↗
arXiv2026

Resolution of outstanding puzzles in $B^+ \!\to K^+ \pi^+ \pi^-$ decays

An amplitude analysis of $B^+ \!\to K^+ \pi^+ \pi^-$ decays is presented, based on $pp$ collision data recorded with the LHCb detector in 2011--2012, corresponding to an integrated luminosity of $3\,\text{fb}^{-1}$. Previous studies of the $B \!\to K \pi \pi$ sector have left key unresolved questions concerning the model of the S-wave contributions. A pivotal finding is that relaxing unitarity-based assumptions about the relation between the $K^*_0(1430)^0$ resonance and the slowly varying scalar part in $K^+\pi^-$ leads to considerably better agreement between the model and data. The $B^+ \!\to K^*_0(1430)^0 \pi^+$ branching fraction now challenges the experimental consensus that $B \!\to K^*_0(1430) \pi$ decays dominate the $B \!\to K \pi \pi$ phase space, aligning with the predictions of QCD factorisation rather than perturbative QCD, thus reversing the agreement found in previous measurements. With this increased flexibility, it also becomes possible to model the scalar $\pi^+ \pi^-$ amplitude using established states, eliminating the need for the ad-hoc ``$f_X(1300)$'' component included in previous analyses of the $B \!\to K\pi\pi$ sector. These advances facilitate the discovery of ten intermediate decays.

hep-ex↗
arXiv2026

Observation of several sources of $C\!P$ violation in $B^+ \!\to K^+ \pi^+ \pi^-$ decays

An amplitude analysis of $B^+ \!\to K^+ \pi^+ \pi^-$ decays is presented in which six $C\!P$-violating phenomena are judged to be of significance for the first time. This analysis is based on $pp$ collision data recorded with the LHCb detector in 2011-2012, corresponding to an integrated luminosity of $3\,\text{fb}^{-1}$. Quasi-two-body $C\!P$ violation in $B^+ \!\to \rho(770)^0 K^+$ decays is discovered, while $C\!P$ violation at amplitude level is established in $B^+ \!\to f_2(1270) K^+$ decays. First evidence for $C\!P$ violation is reported in both the fully elastic S-wave $\pi\pi$-$\pi\pi$ rescattering region and also for any decay involving a spin-3 resonance. Additionally, significant $C\!P$-violation effects are identified in the interference between different $\pi\pi$ partial waves, with observation in S-P wave interference and evidence in S-D wave interference, both of which must be driven by long-distance interactions.

hep-ex↗
arXiv2026

New measurements of $B^+_c$ decays into single charm final states

Using proton-proton collision data corresponding to an integrated luminosity of $9 \,\textrm{fb}^{-1}$ collected by the LHCb experiment, searches are performed for $B^+_c$ mesons decaying to a charm and a charmless meson pair. Five products of branching fraction, ${\cal B}(B^+_c\!\to DX)$, and fragmentation ratio $f_c\big/f_u$ are reported, \begin{align*} R_{D^+ K^{*0}} &= ( 1.42 \pm 0.23 \pm 0.07 \pm 0.11 ) \times 10^{-6}, \\ R_{D^{*0} K^+} &= (1.46 \pm 0.30 \pm 0.11 \pm 0.05 ) \times 10^{-6}, \\ R_{D^+_s \phi}\ \ \ &= ( 4.0\pm 1.3 \pm 0.2 \pm 0.5) \times 10^{-7 }, \\ R_{D^0 K^+}\ &= ( 9.7 \pm 1.0 \pm 0.4 \pm 0.3 ) \times 10^{-7}, \\ R_{D^0 \pi^+}\ &<\ 1.4 \times 10^{-7}\ \text{at 95\% CL}. \end{align*} In each case, the first uncertainty is statistical, the second is systematic and the third includes external uncertainties. The first result is a first observation, the second and third exhibit clear evidence and the fourth improves the precision of previous measurements by a factor two. Additionally, the $CP$ asymmetry in $B^+_c\!\to D^0 K^+$ decays is measured and found to be compatible with zero.

hep-ex↗
arXiv2026

Associated $Z$ + $J/\psi$ production as a probe of multiparton interactions in the forward region

This letter reports a study of associated $Z$ boson and prompt $J/\psi$ production in proton-proton collisions at $\sqrt{s}=13$ TeV with the LHCb detector in the forward rapidity region, using a data sample taken during 2016 to 2018 corresponding to an integrated luminosity of $5.1 \mathrm{fb}^{-1}$. The measured fiducial cross-section is $5.5 \pm 1.5$ pb, significantly exceeding the single-parton scattering expectation of $0.10 \pm 0.08$ pb, indicating that multiparton interactions dominate this process in the explored phase space. Interpreted within the standard double-parton scattering framework, the data yields an effective cross-section $\sigma_{\mathrm{eff}} = 16.6 \pm 4.7$ mb. This provides a direct experimental constraint on the transverse spatial structure of the proton in a kinematic regime characterized simultaneously by small Bjorken-$x$ and an electroweak hard scale set by the $Z$ boson mass.

hep-ex↗
arXiv2026

First evidence of the decay $B^+\to\pi^+ e^+ e^-$

The first evidence for the decay $B^+\to\pi^+ e^+ e^-$ is reported using proton-proton collision data recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb$^{-1}$. A signal excess with a significance of 3.2$\sigma$ is observed and the branching fraction is measured to be $\cal{BR}(B^+\to\pi^+ e^+ e^-) = (2.4\,{}^{+0.9}_{-0.8} \,{}^{+0.4}_{-0.2}) \times 10^{-8}$, where the first set of uncertainties is statistical and the second is systematic. The result is consistent with the Standard Model expectation.

hep-ex↗
arXiv2026

Observation of a new excited charm-strange meson $D_{s1}(2933)^+$ in $B^0\to D^+ D^- K^+ \pi^-$ decays

A new excited charm-strange meson is observed through an amplitude analysis of the full phase space of $B^0\to D^+ D^- K^+ \pi^-$ decays. The analysis is based on a proton-proton collision data sample collected by the \lhcb experiment at a center-of-mass energy $\sqrt{s} = 13\,\text{TeV}$, corresponding to an integrated luminosity of $5.4\text{fb}^{-1}$. The statistical significance of the new state exceeds $10$ standard deviations. Its Breit--Wigner mass and width are measured to be $m_0 = {2933}^{+6}_{-5}(\text{stat})^{+4}_{-3}(\text{syst}) \,\text{MeV} $ and $\Gamma_0 = {72}^{+18}_{-12}(\text{stat})^{+\phantom{0}7}_{-10}(\text{syst}) \,\text{MeV} $, respectively, and its spin-parity quantum numbers are determined to be $J^P = 1^+$. This new meson, denoted as $D_{s1}(2933)^+$, is a candidate for a $D_s(2P^{(\prime)}_{1})^+$ state.

hep-ex↗
arXiv2026

Study of the $B^0 \to \Lambda_c^+ \bar{\Lambda}_c^- K_S^0$ decay

The decay $B^0 \to \Lambda_c^+ \bar{\Lambda}_c^- K_S^0$ is studied at LHCb for the first time using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of 5.4 fb$^{-1}$. The branching ratio relative to the decay $B^+ \to \Lambda_c^+ \bar{\Lambda}_c^- K^+$ is measured to be $$ \frac{{\cal B}(B^0 \to \Lambda_c^+ \bar{\Lambda}_c^- K_S^0)}{{\cal B}(B^+ \to \Lambda_c^+ \bar{\Lambda}_c^- K^+)} = 0.53 \pm 0.05 \pm 0.05, $$ where the first uncertainty is statistical and the second is systematic. Evidence is found for contributions from two resonant states, $\Xi_c(2923)^+$ and $\Xi_c(2939)^+$, in the $\Lambda_c^+ K_S^0$ system. The two states show a significance of $3.9\sigma$ relative to the nonresonant hypothesis. These two $\Xi_c^+$ states are consistent with being the isospin partners of the states observed in $\Lambda_c^+ K^-$ system.

hep-ex↗
arXiv2026

Precision measurement of the muon charge asymmetry from $W$-boson decays in $pp$ collisions at $\sqrt{s}$ = 13 TeV in the forward region

A precision measurement of the muon charge asymmetry from $W$-boson decays in proton-proton collisions at $\sqrt{s}$ = 13 TeV is presented. The analysis utilizes data corresponding to an integrated luminosity of 5.1 $fb^{-1}$, recorded by the LHCb detector during 2016, 2017 and 2018. The asymmetry is measured for muons with transverse momentum between 25 and 55 GeV and pseudorapidity between 2.0 and 4.5. This result represents the most precise determination of the muon charge asymmetry in the forward region to date, exhibiting excellent agreement with next-to-next-to-leading-order predictions in perturbative quantum chromodynamics.

hep-ex↗
arXiv2026

Measurement of the $W$-boson production cross-sections in $pp$ collisions at $\sqrt{s}$ = 13 TeV in the forward region

A precision measurement of the $W$-boson production cross-section is performed using the $W \to \mu\nu$ decay channel, based on a sample of proton-proton collision data collected by the LHCb experiment at $\sqrt{s}$ = 13 TeV and corresponding to an integrated luminosity of 5.1 $fb^{-1}$. The cross-section is measured for muons with transverse momentum between 25 and 55 GeV and pseudorapidity between 2.0 and 4.5. The integrated production cross-sections of $W$ bosons are measured to be $$ \begin{array}{lcl} \sigma_{W^+ \to \mu^+\nu} &=& 1754.2 \pm 1.5 \pm 11.9 \pm 35.1\text{ pb} \\ \sigma_{W^- \to \mu^-\bar{\nu}} &=& 1178.1 \pm 1.3 \pm 9.7 \pm 23.6\text{ pb} \end{array} $$ where uncertainties are statistical, systematic, and due to the luminosity determination, respectively. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. This measurement is significantly more precise than previous results in this kinematic regime.

hep-ex↗
arXiv2026

Measurement of inclusive production of charmonium states in $b$-hadron decays via their decay into $\phi \phi$

The inclusive production of the $\eta_c(1S)$, $\eta_c(2S)$ and $\chi_{c}$ charmonium states in $b$-hadron decays is studied with LHCb Run~2 data, corresponding to an integrated luminosity of $5.9~\text{fb}^{-1}$, using charmonia decays to $\phi\phi$ pairs. The production branching fractions of the $\chi_{c}(1P)$ states in $b$-hadron decays are measured, using $b \to \eta_c(1S) (\to \phi \phi) X$ as a normalisation channel, with $X$ indicating any additional particles. The results are \begin{align*} &{\cal{B}} (b \to \chi_{c0} X) = (1.34 \pm 0.13 \pm 0.06 \pm 0.37) \times 10^{-3}, &{\cal{B}} (b \to \chi_{c1} X) = (1.58 \pm 0.12 \pm 0.09 \pm 0.44) \times 10^{-3}, &{\cal{B}} (b \to \chi_{c2} X) = (0.55 \pm 0.08 \pm 0.05 \pm 0.15) \times 10^{-3}, \end{align*} where the first uncertainty is statistical, the second systematic and the last is due to the limited knowledge of externally measured branching fractions. The production branching fraction of $\eta_c(2S)$ times the branching fraction of its decay into $\phi \phi$ is measured as ${\cal{B}} (b \to \eta_c(2S) X) \times {\cal{B}} (\eta_c(2S) \to \phi \phi) = (4.0 \pm 0.6 \pm 0.6 \pm 1.1) \times 10^{-7}$. Furthermore, the mass of the $\eta_c(1S)$ state is measured to be $M_{\eta_c(1S)} = 2984.1 \pm 0.5 \pm 0.5$ MeV with the best precision to date.

hep-ex↗
arXiv2026

Test of lepton flavour universality with $B^0\to K^{*0}\ell^+\ell^-$ decays at large dilepton invariant mass

Muon-electron universality is tested in $B^0 \to K^{*0} \ \ell^+ \ell^-$ decays, in the dilepton-invariant-mass region above the $\psi(2S)$ resonance. The analysis uses beauty mesons produced in proton-proton collisions recorded by the LHCb detector at center-of-mass energies of 7, 8, and 13 $\text{TeV}$, corresponding to an integrated luminosity of 9 $\text{fb}^{-1}$. The ratio of branching fractions between the muon and electron channels $R_{K^{*0}}$ is measured to be $1.08\,^{+0.14}_{-0.12}\text{(stat)} \ \pm 0.07\text{(syst)}$ for a dilepton-invariant-mass squared above 14.0 $\text{GeV}^{2}/\text{c}^{4}$, consistent with the standard model prediction. This result represents the most precise measurement of $R_{K^{*0}}$ in this region and the first such measurement performed at a hadron collider.

hep-ex↗
arXiv2026

Search for the decays $B_{(s)}^0\to J/\psi\gamma$ at LHCb

A search for the rare decays $B_{(s)}^0\to J/\psi\gamma$ is performed with proton-proton collision data collected by the LHCb experiment, corresponding to integrated luminosities of $3~\rm{fb}^{-1}$ at centre-of-mass energies of 7 and 8 TeV, and $6~\rm{fb}^{-1}$ at 13 TeV. Assuming no contribution from $B^0\to J/\psi\gamma$ decay, an upper limit is set on the branching fraction $\mathcal{B}(B_{s}^0\to J/\psi\gamma)<2.9\times10^{-6}$ at the 90% confidence level. If instead no contribution from $B_{s}^0\to J/\psi\gamma$ decay is assumed, the limit is $\mathcal{B}(B^0\to J/\psi\gamma)<2.5\times10^{-6}$ at the 90% confidence level. These results supersede the previous LHCb results, with the limit for $B_{s}^0\to J/\psi\gamma$ improved by a factor of 2.5.

hep-ex↗
arXiv2026

Measurement of CP asymmetries in $\kern 0.18em\overline{\kern -0.18em B}^0 \to D_s^- D^+$ and $\kern 0.18em\overline{\kern -0.18em B}_s^0 \to D_s^+ D^-$ decays

Measurements of the combined CP asymmetries in $\kern 0.18em\overline{\kern -0.18em B}^0 \to D_s^- D^+$ and $\kern 0.18em\overline{\kern -0.18em B}_s^0 \to D_s^+ D^-$ decays are made using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9fb$^{-1}$. The measurements are found to be \begin{aligned} A_{CP}(\kern 0.18em\overline{\kern -0.18em B}^0 \to D_s^- D^+) &= 0.0009 \pm 0.0053 \pm 0.0040, \\ A_{CP}(\kern 0.18em\overline{\kern -0.18em B}_s^0 \to D_s^+ D^-) &= 0.103\phantom{0} \pm 0.053\phantom{0} \pm 0.010, \end{aligned} where the first and second uncertainties are statistical and systematic, respectively. This is the first measurement of this asymmetry in $\kern 0.18em\overline{\kern -0.18em B}_s^0$ decays, and the most precise measurement to date for $\kern 0.18em\overline{\kern -0.18em B}^0$ decays. Both measurements are found to be consistent with CP symmetry.

hep-ex↗
arXiv2026

$B$-jet fragmentation with $B^{\pm} \to J/\psi K^{\pm}$ decays in $\sqrt{s} = 13$ TeV $pp$ collisions at LHCb

The collinear and transverse-momentum-dependent jet fragmentation function and the radial profile for $B^{\pm}$ mesons in jets are measured. The $B^{\pm}$ mesons are reconstructed through the $J/\psi (\to \mu^{+} \mu^{-}) K^{\pm}$ decay channel using proton-proton collision data collected during 2016-2018 with the LHCb detector at a center-of-mass energy of $\sqrt{s}=13$ TeV, corresponding to an integrated luminosity of $5.4$ fb$^{-1}$. The results complement recent measurements of jet fragmentation functions for heavy-flavor hadrons and suggest a growing contribution of gluon fragmentation to $B^{\pm}$ mesons as the jet transverse momentum increases.

hep-ex↗
arXiv2026

First measurement of time-dependent $CP$ violation in the flavor-changing neutral-current decay $B^{0}\rightarrow K_{S}^{0}\mu^{+}\mu^{-}$

A flavor-tagged time-dependent analysis of $B^{0}\rightarrow K_{S}^{0}\mu^{+}\mu^{-}$ decays is performed across the full dimuon mass range excluding the $J/\psi$ and $\psi(2S)$ resonance regions. The analysis uses proton-proton collision data collected by the LHCb experiment in 2011--2018 at center-of-mass energies of 7, 8 and 13TeV, corresponding to an integrated luminosity of 9$fb^{-1}$. The CP violation parameters are determined to be $C=-0.13 \pm 0.32 \pm 0.04$ and $S= +0.82\pm 0.29 \pm 0.05$, where the first uncertainties are statistical and the second are systematic. The results are consistent with the Standard Model prediction. This is the first experimental study of time-dependent CP violation in $b\rightarrow sl^{+}l^{-}$ processes.

hep-ex↗
arXiv2026

Measurement of the local and nonlocal amplitudes in $B^{+}\to K^{+}\mu^{+}\mu^{-}$ decays

This paper presents a thorough study of the local and nonlocal amplitudes in $B^+ \to K^+\mu^+\mu^-$ 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 8.4fb$^{-1}$ collected by the LHCb experiment. 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 $C_9+C_9'$ and $C_{10}+C_{10}'$ with the Standard Model prediction is found to vary between $1.6\,\sigma$ and $4\,\sigma$, depending on the choice of local form factors.

hep-ex↗