Search

We report a measurement of cross section $\sigma ({\nu }_{\mu }+\text{nucleus}\to {\mu }^{-}+X)$ and the first measurements of the cross section $\sigma ({\overline{\nu }}_{\mu }+\text{nucleus}\to {\mu }^{+}+X)$ and their ratio $R(\frac{\sigma (\overline{\nu })}{\sigma (\nu )})$ at (anti) neutrino energies below 1.5 GeV. We determine the single momentum bin cross section measurements, averaged over the T2K $\overline{\nu }/\nu$-flux, for the detector target material (mainly carbon, oxygen, hydrogen and copper) with phase space restricted laboratory frame kinematics of ${\theta }_{\mu }<32°$ and $p_{\mu }>500\mathrm{MeV}/c$. The results are $\sigma (\overline{\nu })=(0.900\pm 0.029(\mathrm{stat})\pm 0.088(\mathrm{syst}))\times {10}^{-39}$ and $\sigma (\nu )=(2.41\pm 0.022(\mathrm{stat})\pm 0.231(\mathrm{syst}))\times {10}^{-39}$ in units of ${\mathrm{cm}}^2/\mathrm{nucleon}$ and $R(\frac{\sigma (\overline{\nu })}{\sigma (\nu )})=0.373\pm 0.012(\mathrm{stat})\pm 0.015(\mathrm{syst})$.

We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment. With data corresponding to $1.43\times {10}^{20}$ protons on target, we observe 31 fully-contained single $\mu$-like ring events in Super-Kamiokande, compared with an expectation of $104\pm 14(\mathrm{syst})$ events without neutrino oscillations. The best-fit point for two-flavor ${\nu }_{\mu }\to {\nu }_{\tau }$ oscillations is ${sin}^2(2{\theta }_{23})=0.98$ and $|\Delta m_{32}^2|=2.65\times {10}^{-3}{\mathrm{eV}}^2$. The boundary of the 90% confidence region includes the points $({sin}^2(2{\theta }_{23}),|\Delta m_{32}^2|)=(1.0,3.1\times {10}^{-3}{\mathrm{eV}}^2)$, (0.84, $2.65\times {10}^{-3}{\mathrm{eV}}^2$) and (1.0, $2.2\times {10}^{-3}{\mathrm{eV}}^2$).

T2K has performed the first measurement of ${\nu }_{\mu }$ inclusive charged current interactions on carbon at neutrino energies of $\sim 1\mathrm{GeV}$ where the measurement is reported as a flux-averaged double differential cross section in muon momentum and angle. The flux is predicted by the beam Monte Carlo and external data, including the results from the NA61/SHINE experiment. The data used for this measurement were taken in 2010 and 2011, with a total of $10.8\times {10}^{19}$ protons-on-target. The analysis is performed on 4485 inclusive charged current interaction candidates selected in the most upstream fine-grained scintillator detector of the near detector. The flux-averaged total cross section is $⟨{\sigma }_{\mathrm{CC}}{⟩}_{\varphi }=(6.91\pm 0.13(\mathrm{stat})\pm 0.84(\mathrm{syst}))\times {10}^{-39}\frac{{\mathrm{cm}}^2}{\mathrm{nucleon}}$ for a mean neutrino energy of 0.85 GeV.

We report a measurement of the flux-integrated cross section for inclusive muon neutrino charged-current interactions on carbon. The double-differential measurements are given as a function of the muon momentum and angle. Relative to our previous publication on this topic, these results have an increased angular acceptance and higher statistics. The data sample presented here corresponds to $5.7\times {10}^{20}$ protons on target. The total flux-integrated cross section is measured to be $(6.950\pm 0.662)\times {10}^{-39}{\mathrm{cm}}^2{\text{nucleon}}^{-1}$ and is consistent with our simulation.

Neutrino- and antineutrino-oxygen neutral-current quasielasticlike interactions are measured at Super-Kamiokande using nuclear deexcitation $\gamma$ rays to identify signal-like interactions in data from a $14.94(16.35)\times {10}^{20}$ protons-on-target exposure of the T2K neutrino (antineutrino) beam. The measured flux-averaged cross sections on oxygen nuclei are $⟨{\sigma }_{\nu \text{−}\mathrm{NCQE}}⟩=1.70\pm 0.17(\mathrm{stat}.{)}_{-0.38}^{+0.51}(\mathrm{syst}.)\times {10}^{-38}{\mathrm{cm}}^2/\text{oxygen}$ with a flux-averaged energy of 0.82 GeV and $⟨{\sigma }_{\overline{\nu }\text{−}\mathrm{NCQE}}⟩=0.98\pm 0.16(\mathrm{stat}.{)}_{-0.19}^{+0.26}(\mathrm{syst}.)\times {10}^{-38}{\mathrm{cm}}^2/\text{oxygen}$ with a flux-averaged energy of 0.68 GeV, for neutrinos and antineutrinos, respectively. These results are the most precise to date, and the antineutrino result is the first cross section measurement of this channel. They are compared with various theoretical predictions. The impact on evaluation of backgrounds to searches for supernova relic neutrinos at present and future water Cherenkov detectors is also discussed.

The single ${\pi }^0$ production rate in neutral current neutrino interactions on water in a neutrino beam with a peak neutrino energy of 0.6 GeV has been measured using the PØD, one of the subdetectors of the T2K near detector. The production rate was measured for data taking periods when the PØD contained water ($2.64\times {10}^{20}$ protons-on-target) and also periods without water ($3.49\times {10}^{20}$ protons-on-target). A measurement of the neutral current single ${\pi }^0$ production rate on water is made using appropriate subtraction of the production rate with water in from the rate with water out of the target region. The subtraction analysis yields $106\pm 41\pm 69$ signal events where the uncertainties are statistical (stat.) and systematic (sys.) respectively. This is consistent with the prediction of 157 events from the nominal simulation. The measured to expected ratio is $0.68\pm 0.26(\mathrm{stat})\pm 0.44(\mathrm{sys})\pm 0.12(\mathrm{flux})$. The nominal simulation uses a flux integrated cross section of $7.63\times {10}^{-39}{\mathrm{cm}}^2$ per nucleon with an average neutrino interaction energy of 1.3 GeV.

We report measurements by the T2K experiment of the parameters ${\theta }_{23}$ and $\mathrm{\Delta }{m}_{32}^2$, which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2K’s neutrino energy and propagation distance. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, muon-like events from each beam mode are used to measure these parameters separately for neutrino and antineutrino oscillations. Data taken from $1.49\times {10}^{21}$ protons on target (POT) in neutrino mode and $1.64\times {10}^{21}$ POT in antineutrino mode are used. The best-fit values obtained by T2K were ${\sin }^2({\theta }_{23})={0.51}_{-0.07}^{+0.06}({0.43}_{-0.05}^{+0.21})$ and $\mathrm{\Delta }{m}_{32}^2={2.47}_{-0.09}^{+0.08}({2.50}_{-0.13}^{+0.18})\times {10}^{-3}{\mathrm{eV}}^2/c^4$ for neutrinos (antineutrinos). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed. An analysis using an effective two-flavor neutrino oscillation model where the sine of the mixing angle is allowed to take nonphysical values larger than 1 is also performed to check the consistency of our data with the three-flavor model. Our data were found to be consistent with a physical value for the mixing angle.

“Beta beams” produce collimated pure electron (anti)neutrino beams by accelerating beta active ions to high energies and having them decay in a racetrack shaped storage ring of 7 km circumference, the decay ring. EUROnu beta beams are based on CERN infrastructures and existing machines. Using existing machines may be an advantage for the cost evaluation, but will also constrain the physics performance. The isotope pair of choice for the beta beam is ${}^6\mathrm{He}$ and ${}^{18}\mathrm{Ne}$. However, before the EUROnu studies one of the required isotopes, ${}^{18}\mathrm{Ne}$, could not be produced in rates that satisfy the needs for physics of the beta beam. Therefore, studies of alternative beta emitters, ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$, with properties interesting for a beta beam have been proposed and have been studied within EUROnu. These alternative isotopes could be produced by using a small storage ring, in which the beam traverses a target, creating the ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ isotopes. This production ring, the injection linac and the target system have been evaluated. Measurements of the cross section of the reactions to produce the beta beam isotopes show interesting results. A device to collect the produced isotopes from the target has been developed and tested. However, the yields of ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$, using the production ring for production of ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$, is not yet, according to simulations, giving the rates of isotopes that would be needed. Therefore, a new method of producing the ${}^{18}\mathrm{Ne}$ isotope has been developed and tested giving good production rates. A 60 GHz ECRIS prototype, the first in the world, was developed and tested for ion production with contributions from EUROnu. The decay ring lattices for the ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ have been developed and the lattice for ${}^6\mathrm{He}$ and ${}^{18}\mathrm{Ne}$ has been optimized to ensure the high intensity ion beam stability.

The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Fréjus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of and beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular and , also stored in a ring. The far detector is also the MEMPHYS detector in the Fréjus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the physics reach of each facility, in particular for the measurement of violation in the lepton sector, and estimated the cost of construction. These have demonstrated that the best facility to build is the Neutrino Factory. However, if a powerful proton driver is constructed for another purpose or if the MEMPHYS detector is built for astroparticle physics, the Super Beam also becomes very attractive.

MEMPHYS (MEgaton Mass PHYSics) is a proposed large-scale water-Cherenkov experiment to be performed deep underground. It is dedicated to nucleon decay searches and the detection of neutrinos from supernovae, solar, and atmospheric neutrinos, as well as neutrinos from a future beam to measure the $CP$ violating phase in the leptonic sector and the mass hierarchy. This paper provides an overview of the latest studies on the expected performance of MEMPHYS in view of detailed estimates of its physics reach, mainly concerning neutrino beams.

The T2K experiment has reported the first observation of the appearance of electron neutrinos in a muon neutrino beam. The main and irreducible background to the appearance signal comes from the presence in the neutrino beam of a small intrinsic component of electron neutrinos originating from muon and kaon decays. In T2K, this component is expected to represent 1.2% of the total neutrino flux. A measurement of this component using the near detector (ND280), located 280 m from the target, is presented. The charged current interactions of electron neutrinos are selected by combining the particle identification capabilities of both the time projection chambers and electromagnetic calorimeters of ND280. The measured ratio between the observed electron neutrino beam component and the prediction is $1.01\pm 0.10$ providing a direct confirmation of the neutrino fluxes and neutrino cross section modeling used for T2K neutrino oscillation analyses. Electron neutrinos coming from muons and kaons decay are also separately measured, resulting in a ratio with respect to the prediction of $0.68\pm 0.30$ and $1.10\pm 0.14$, respectively.

We report the first measurement of the neutrino-oxygen neutral-current quasielastic (NCQE) cross section. It is obtained by observing nuclear deexcitation $\gamma$ rays which follow neutrino-oxygen interactions at the Super-Kamiokande water Cherenkov detector. We use T2K data corresponding to $3.01\times 10^{20}$ protons on target. By selecting only events during the T2K beam window and with well-reconstructed vertices in the fiducial volume, the large background rate from natural radioactivity is dramatically reduced. We observe 43 events in the 4–30 MeV reconstructed energy window, compared with an expectation of 51.0, which includes an estimated 16.2 background events. The background is primarily nonquasielastic neutral-current interactions and has only 1.2 events from natural radioactivity. The flux-averaged NCQE cross section we measure is $1.55\times 10^{-38}{\mathrm{cm}}^2$ with a 68% confidence interval of $(1.22,2.20)\times 10^{-38}{\mathrm{cm}}^2$ at a median neutrino energy of 630 MeV, compared with the theoretical prediction of $2.01\times 10^{-38}{\mathrm{cm}}^2$.

This paper reports measurements of final-state proton multiplicity, muon and proton kinematics, and their correlations in charged-current pionless neutrino interactions, measured by the T2K ND280 near detector in its plastic scintillator (${\mathrm{C}}_8{\mathrm{H}}_8$) target. The data were taken between years 2010 and 2013, corresponding to approximately $6\times {10}^{20}$ protons on target. Thanks to their exploration of the proton kinematics and of imbalances between the proton and muon kinematics, the results offer a novel probe of the nuclear-medium effects most pertinent to the (sub-)GeV neutrino-nucleus interactions that are used in accelerator-based long-baseline neutrino oscillation measurements. These results are compared to many neutrino-nucleus interaction models which all fail to describe at least part of the observed phase space. In case of events without a proton above a detection threshold in the final state, a fully consistent implementation of the local Fermi gas model with multinucleon interactions gives the best description of the data. In the case of at least one proton in the final state, the spectral function model agrees well with the data, most notably when measuring the kinematic imbalance between the muon and the proton in the plane transverse to the incoming neutrino. Within the models considered, only the existence of multinucleon interactions are able to describe the extracted cross section within regions of high transverse kinematic imbalance. The effect of final-state interactions is also discussed.

The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of $14.7(7.6)\times {10}^{20}$ protons on target in the neutrino (antineutrino) mode, 89 ${\nu }_e$ candidates and seven anti-${\nu }_e$ candidates are observed, while 67.5 and 9.0 are expected for ${\delta }_{CP}=0$ and normal mass ordering. The obtained $2\sigma$ confidence interval for the $CP$-violating phase, ${\delta }_{CP}$, does not include the $CP$-conserving cases (${\delta }_{CP}=0$, $\pi$). The best-fit values of other parameters are ${\sin }^2{\theta }_{23}=0.526_{-0.036}^{+0.032}$ and $\mathrm{\Delta }{m}_{32}^2={2.463}_{-0.070}^{+0.071}\times {10}^{-3}{\mathrm{eV}}^2/c^4$.

We report the first measurement of the flux-averaged cross section for charged current coherent ${\pi }^{+}$ production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured flux-averaged cross sections are below those predicted by both the Rein-Sehgal and Alvarez-Ruso et al. models.

This paper reports a measurement by the T2K experiment of the ${\nu }_{\mu }$ charged current quasielastic (CCQE) cross section on a carbon target with the off-axis detector based on the observed distribution of muon momentum ($p_{\mu }$) and angle with respect to the incident neutrino beam (${\theta }_{\mu }$). The flux-integrated CCQE cross section was measured to be $⟨\sigma ⟩=(0.83\pm 0.12)\times {10}^{-38}{\mathrm{cm}}^2$. The energy dependence of the CCQE cross section is also reported. The axial mass, $M_A^{\mathrm{QE}}$, of the dipole axial form factor was extracted assuming the Smith-Moniz CCQE model with a relativistic Fermi gas nuclear model. Using the absolute (shape-only) $p_{\mu }\text{−}\cos {\theta }_{\mu }$ distribution, the effective $M_A^{\mathrm{QE}}$ parameter was measured to be $1.26_{-0.18}^{+0.21}\mathrm{GeV}/c^2$ ($1.43_{-0.22}^{+0.28}\mathrm{GeV}/c^2$).

In this paper, we study scalar mediator induced nonstandard interactions (SNSIs) in the context of the ESSnuSB experiment. In particular, we study the capability of ESSnuSB to put bounds on the SNSI parameters and also study the impact of SNSIs in the measurement of the leptonic $CP$ phase ${\delta }_{CP}$. Existence of SNSIs modifies the neutrino mass matrix and this modification can be expressed in terms of three diagonal real parameters (${\eta }_{ee}$, ${\eta }_{\mu \mu }$, and ${\eta }_{\tau \tau }$) and three off-diagonal complex parameters (${\eta }_{e\mu }$, ${\eta }_{e\tau }$, and ${\eta }_{\mu \tau }$). Our study shows that the upper bounds on the parameters ${\eta }_{\mu \mu }$ and ${\eta }_{\tau \tau }$ depend upon how $\mathrm{\Delta }{m}_{31}^2$ is minimized in the theory. However, this is not the case when one tries to measure the impact of SNSIs on ${\delta }_{CP}$. Further, we show that the $CP$ sensitivity of ESSnuSB can be completely lost for certain values of ${\eta }_{ee}$ and ${\eta }_{\mu \tau }$ for which the appearance channel probability becomes independent of ${\delta }_{CP}$.

We report the first measurement of neutron capture multiplicity in neutrino-oxygen neutral-current quasielasticlike interactions at the gadolinium-loaded Super-Kamiokande detector using the T2K neutrino beam, which has a peak energy of about 0.6 GeV. A total of 30 neutral-current quasielasticlike event candidates were selected from T2K data corresponding to an exposure of $1.76\times {10}^{20}$ protons on target. The $\gamma$ ray signals resulting from neutron captures were identified using a neural network. The flux-averaged mean neutron capture multiplicity was measured to be ${1.37\pm 0.33(\mathrm{stat}.)}_{-0.27}^{+0.17}(\mathrm{syst}.)$, which is compatible within 2.3 sigma than predictions obtained using our nominal simulation. We discuss potential sources of systematic uncertainty in the prediction and demonstrate that a significant portion of this discrepancy arises from the modeling of hadron-nucleus interactions in the detector medium.

The Super-Kamiokande and T2K Collaborations present a joint measurement of neutrino oscillation parameters from their atmospheric and beam neutrino data. It uses a common interaction model for events overlapping in neutrino energy and correlated detector systematic uncertainties between the two datasets, which are found to be compatible. Using 3244.4 days of atmospheric data and a beam exposure of $19.7(16.3)\times {10}^{20}$ protons on target in (anti)neutrino mode, the analysis finds a $1.9\sigma$ exclusion of $CP$ conservation (defined as $J_{CP}=0$) and a $1.2\sigma$ exclusion of the inverted mass ordering.