Search

One of the main goals of the Long Baseline Neutrino Observatory (LBNO) is to study the $L/E$ behaviour (spectral information) of the electron neutrino and antineutrino appearance probabilities, in order to determine the unknown CP-violation phase $\delta_{CP}$ and discover CP-violation in the leptonic sector. The result is based on the measurement of the appearance probabilities in a broad range of energies, covering t he 1st and 2nd oscillation maxima, at a very long baseline of 2300 km. The sensitivity of the experiment can be maximised by optimising the energy spectra of the neutrino and anti-neutrino fluxes. Such an optimisation requires exploring an extended range of parameters describing in details the geometries and properties of the primary protons, hadron target and focusing elements in the neutrino beam line. In this paper we present a numerical solution that leads to an optimised energy spectra and study its impact on the sensitivity of LBNO to discover leptonic CP violation. In the optimised flux both 1st and 2nd oscillation maxima play an important role in the CP sensitivity. The studies also show that this configuration is less sensitive to systematic errors (e.g. on the total event rates) than an experiment which mainly relies on the neutrino-antineutrino asymmetry at the 1st maximum to determine the existence of CP-violation.

The proposed Long Baseline Neutrino Observatory (LBNO) initially consists of $\sim 20$ kton liquid double phase TPC complemented by a magnetised iron calorimeter, to be installed at the Pyh\"asalmi mine, at a distance of 2300 km from CERN. The conventional neutrino beam is produced by 400 GeV protons accelerated at the SPS accelerator delivering 700 kW of power. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the $L/E$ behaviour, and distinguishing effects arising from $\delta_{CP}$ and matter. In this paper we show how this comprehensive physics case can be further enhanced and complemented if a neutrino beam produced at the Protvino IHEP accelerator complex, at a distance of 1160 km, and with modest power of 450 kW is aimed towards the same far detectors. We show that the coupling of two independent sub-MW conventional neutrino and antineutrino beams at different baselines from CERN and Protvino will allow to measure CP violation in the leptonic sector at a confidence level of at least $3\sigma$ for 50\% of the true values of $\delta_{CP}$ with a 20 kton detector. With a far detector of 70 kton, the combination allows a $3\sigma$ sensitivity for 75\% of the true values of $\delta_{CP}$ after 10 years of running. Running two independent neutrino beams, each at a power below 1 MW, is more within today's state of the art than the long-term operation of a new single high-energy multi-MW facility, which has several technical challenges and will likely require a learning curve.

In June 2012, an Expression of Interest for a long-baseline experiment (LBNO) has been submitted to the CERN SPSC. LBNO considers three types of neutrino detector technologies: a double-phase liquid argon (LAr) TPC and a magnetised iron detector as far detectors. For the near detector, a high-pressure gas TPC embedded in a calorimeter and a magnet is the baseline design. A mandatory milestone is a concrete prototyping effort towards the envisioned large-scale detectors, and an accompanying campaign of measurements aimed at assessing the detector associated systematic errors. The proposed $6\times 6\times 6$m$^3$ DLAr is an industrial prototype of the design discussed in the EoI and scalable to 20 kton or 50~kton. It is to be constructed and operated in a controlled laboratory and surface environment with test beam access, such as the CERN North Area (NA). Its successful operation and full characterisation will be a fundamental milestone, likely opening the path to an underground deployment of larger detectors. The response of the DLAr demonstrator will be measured and understood with an unprecedented precision in a charged particle test beam (0.5-20 GeV/c). The exposure will certify the assumptions and calibrate the response of the detector, and allow to develop and to benchmark sophisticated reconstruction algorithms, such as those of 3-dimensional tracking, particle ID and energy flow in liquid argon. All these steps are fundamental for validating the correctness of the physics performance described in the LBNO EoI., Comment: 217 pages, 164 figures, LBNO-DEMO (CERN WA105) Collaboration

see paper for full list of authors; This Expression of Interest (EoI) describes the motivation for and the feasibility studies of a long baseline neutrino oscillation experiment (LBNO) with a new conventional neutrino beamline facility (CN2PY). The beam will be aimed at a next generation deep-underground neutrino observatory comprising a double phase liquid argon (LAr) detector and a magnetized iron calorimeter, located at the Pyhäsalmi (Finland) mine at a distance of 2300~km. The double phase LAr Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC) is known to provide excellent tracking and calorimetry performance that can outperform other techniques. An initial 20~kton LAr fiducial volume, as considered here, comparable to the fiducial mass of SuperKamiokande and NOvA, offers a new insight and an increase in sensitivity reach for many physics channels. A magnetized iron calorimeter with muon momentum and charge determination collects an independent neutrino sample, and serves as a tail catcher for CERN beam events occurring in the LAr target. The long baseline physics objectives comprise the precise investigation of all flavor oscillations ($\nu_\mu\rightarrow \nu_\mu$, $\nu_\mu\rightarrow \nu_\tau$, $\nu_\mu\rightarrow \nu_e$) with neutrinos and antineutrinos, exploiting the energy spectrum information of the oscillation probability ($L/E$ method) in appearance and disappearance modes, to provide unambiguous sensitivity to oscillation parameters, and a stringent test of the 3-generation mixing. The existence of CP-violation will be tested explicitly, which is different from simply extracting the $\delta_{CP}$ violating phase from global fits of all available data. With an exposure of $2.25\times 10^{20}$~p.o.t. from the SPS at 400~GeV, a conclusive determination ($>5\sigma$~C.L.) of the neutrino mass hierarchy is possible for \emph{any} value of $\delta_{CP}$. Although limited by statistics in the initial configuration, the $L/E$ method also yields a clean measurement of the CP-violating phase. With $1\times 10^{21}$~p.o.t., the existence of CP-violation (CPV) can be demonstrated at the 90\%C.L. for $\sim 60\%$ of the $\delta_{CP}$ parameter space. This CPV-sensitivity is achievable in $\sim$12~years at the upgraded SPS. It improves further with the increased exposure resulting from longer running periods and/or an increase in beam power and far detector mass. With the chosen location in the deepest mine in Europe at $-1440$~m ($\sim$4000~m.w.e.), the already very large initial target mass provides an unique opportunity to observe new rare phenomena, independently of the CERN beam events. In the GeV range, evidence for Grand Unified Theories (GUT) can be searched for with nucleon decay signals. From 100~MeV to tens of GeV, the collection of thousands of atmospheric electron and muon neutrinos with good energy resolution and particle identification over a very large range of energies (SubGeV and MultiGeV) improves our understanding of this source and yields information on subleading oscillation effects, which provide additional and complementary sensitivity to the oscillation phenomenology including $\theta_{13}$, matter effects and possibly the CP-phase. At high energy, it allows an identification with high statistical significance and a study of $\nu_\tau$ appearance in atmospheric events. Below 100~MeV, neutrinos from a new galactic supernova burst would be recorded with large statistics, addressing the astrophysics of the supernova and neutrino flavor oscillations through the SN and Earth matter. Neutrinos from relic supernovae could also be potentially detected, depending on their flux and prevailing backgrounds. LBNO can also potentially detect as-of-yet unknown sources of astrophysical neutrinos, like for instance those that could arise from annihilation processes of WIMP particles in astrophysical objects, and study their flavor composition. The plan described so far is augmented with a concrete upgrade path to evolve towards an ultimate volume observatory by additional units of increasingly larger masses. With a three-fold increase in exposure (defined as the product neutrino beam power $\times$ far detector target mass), CPV becomes accessible at $>3\sigma$~C.L. for 75\% of the $\delta_{CP}$ parameter space, assuming that all systematic errors can be controlled below the 5\% level. The LBNO far site at 2300~km from CERN could also represent the first step towards a Neutrino Factory project based on the decays of muons in the straight sections of a storage ring. Based on the expertise present at CERN and in European and in international research groups, and building upon the results of several years of EU-funded design studies, we are confident that the technology for the beam and detectors is sufficiently mature to allow for an early start to realizing the facility. We are calling on CERN to promptly support and engage in the prototyping of the near and far detector components, to investigate options for campaigns of detector performance characterization and calibration with test beams in the North Area, and engage in a collaborative effort with the LBNO Collaboration that should lead to a full engineering design of the CN2PY beam and to an LBNO Proposal by the end of 2014.

In June 2012, an Expression of Interest for a long-baseline experiment (LBNO, CERN-SPSC-EOI-007) has been submitted to the CERN SPSC and is presently under review. LBNO considers three types of neutrino detector technologies: a double-phase liquid argon (LAr) TPC and a magnetised iron detector as far detectors. For the near detector, a high-pressure gas TPC embedded in a calorimeter and a magnet is the baseline design. A mandatory milestone in view of any future long baseline experiment is a concrete prototyping effort towards the envisioned large-scale detectors, and an accompanying campaign of measurements aimed at assessing the systematic errors that will be affecting their intended physics programme. Following an encouraging feedback from 108th SPSC on the technology choices, we have defined as priority the construction and operation of a $6\times 6\times 6$m$^3$ (active volume) double-phase liquid argon (DLAr) demonstrator, and a parallel development of the technologies necessary for large magnetised MIND detectors. The $6\times 6\times 6$m$^3$ DLAr is an industrial prototype of the design proposed in the EoI and scalable to 20 kton, 50~kton or more. It is to be constructed and operated in a controlled laboratory and surface environment with test beam access, such as the CERN North Area (NA). Its successful operation and full characterisation will be a fundamental milestone, likely opening the path to an underground deployment of larger detectors. The response of the DLAr demonstrator will be measured and understood with an unprecedented precision in a charged particle test beam (0.5-20 GeV/c). The exposure will certify the assumptions and calibrate the response of the detector, and allow to develop and to benchmark sophisticated reconstruction algorithms, such as those of 3-dimensional tracking, particle ID and energy flow in liquid argon. All these steps are fundamental for validating the correctness of the physics performance described in the LBNO EoI. We anticipate that a successful operation of the double-phase \six DLAr demonstrator and its campaign exposure to a charged particle beam, will provide very important and vital feedback for long baseline programmes, and in general for the field. It will represent a never-achieved milestone for LAr detectors. Its design specifically addresses and represents a concrete step towards an extrapolation of the technology to very large masses in the tens of kton range, such as the one considered and studied for several years within the EU FP7 funded LAGUNA/LAGUNA-LBNO design studies. The parameters of the demonstrator will be directly scalable and the components mass-produceable. Long drift paths will be assessed on a large scale. As requested by SPSC, we submit a Technical Design Report, in view of a realisation of the facility and an exposure to the charged particle beam before the LHC LS2. In June 2012, an Expression of Interest for a long-baseline experiment (LBNO) has been submitted to the CERN SPSC. LBNO considers three types of neutrino detector technologies: a double-phase liquid argon (LAr) TPC and a magnetised iron detector as far detectors. For the near detector, a high-pressure gas TPC embedded in a calorimeter and a magnet is the baseline design. A mandatory milestone is a concrete prototyping effort towards the envisioned large-scale detectors, and an accompanying campaign of measurements aimed at assessing the detector associated systematic errors. The proposed $6\times 6\times 6$m$^3$ DLAr is an industrial prototype of the design discussed in the EoI and scalable to 20 kton or 50~kton. It is to be constructed and operated in a controlled laboratory and surface environment with test beam access, such as the CERN North Area (NA). Its successful operation and full characterisation will be a fundamental milestone, likely opening the path to an underground deployment of larger detectors. The response of the DLAr demonstrator will be measured and understood with an unprecedented precision in a charged particle test beam (0.5-20 GeV/c). The exposure will certify the assumptions and calibrate the response of the detector, and allow to develop and to benchmark sophisticated reconstruction algorithms, such as those of 3-dimensional tracking, particle ID and energy flow in liquid argon. All these steps are fundamental for validating the correctness of the physics performance described in the LBNO EoI.

This Expression of Interest (EoI) describes the motivation for and the feasibility studies of a long baseline neutrino oscillation experiment (LBNO) with a new conventional neutrino beamline facility (CN2PY). The beam will be aimed at a next generation deep-underground neutrino observatory comprising a double phase liquid argon (LAr) detector and a magnetized iron calorimeter, located at the Pyh\"asalmi (Finland) mine at a distance of 2300~km. The double phase LAr Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC) is known to provide excellent tracking and calorimetry performance that can outperform other techniques. An initial 20~kton LAr fiducial volume, as considered here, comparable to the fiducial mass of SuperKamiokande and NOvA, offers a new insight and an increase in sensitivity reach for many physics channels. A magnetized iron calorimeter with muon momentum and charge determination collects an independent neutrino sample, and serves as a tail catcher for CERN beam events occurring in the LAr target. The long baseline physics objectives comprise the precise investigation of all flavor oscillations ($\nu_\mu\rightarrow \nu_\mu$, $\nu_\mu\rightarrow \nu_\tau$, $\nu_\mu\rightarrow \nu_e$) with neutrinos and antineutrinos, exploiting the energy spectrum information of the oscillation probability ($L/E$ method) in appearance and disappearance modes, to provide unambiguous sensitivity to oscillation parameters, and a stringent test of the 3-generation mixing. The existence of CP-violation will be tested explicitly, which is different from simply extracting the $\delta_{CP}$ violating phase from global fits of all available data. With an exposure of $2.25\times 10^{20}$~p.o.t. from the SPS at 400~GeV, a conclusive determination ($>5\sigma$~C.L.) of the neutrino mass hierarchy is possible for \emph{any} value of $\delta_{CP}$. Although limited by statistics in the initial configuration, the $L/E$ method also yields a clean measurement of the CP-violating phase. With $1\times 10^{21}$~p.o.t., the existence of CP-violation (CPV) can be demonstrated at the 90\%C.L. for $\sim 60\%$ of the $\delta_{CP}$ parameter space. This CPV-sensitivity is achievable in $\sim$12~years at the upgraded SPS. It improves further with the increased exposure resulting from longer running periods and/or an increase in beam power and far detector mass. With the chosen location in the deepest mine in Europe at $-1440$~m ($\sim$4000~m.w.e.), the already very large initial target mass provides an unique opportunity to observe new rare phenomena, independently of the CERN beam events. In the GeV range, evidence for Grand Unified Theories (GUT) can be searched for with nucleon decay signals. From 100~MeV to tens of GeV, the collection of thousands of atmospheric electron and muon neutrinos with good energy resolution and particle identification over a very large range of energies (SubGeV and MultiGeV) improves our understanding of this source and yields information on subleading oscillation effects, which provide additional and complementary sensitivity to the oscillation phenomenology including $\theta_{13}$, matter effects and possibly the CP-phase. At high energy, it allows an identification with high statistical significance and a study of $\nu_\tau$ appearance in atmospheric events. Below 100~MeV, neutrinos from a new galactic supernova burst would be recorded with large statistics, addressing the astrophysics of the supernova and neutrino flavor oscillations through the SN and Earth matter. Neutrinos from relic supernovae could also be potentially detected, depending on their flux and prevailing backgrounds. LBNO can also potentially detect as-of-yet unknown sources of astrophysical neutrinos, like for instance those that could arise from annihilation processes of WIMP particles in astrophysical objects, and study their flavor composition. The plan described so far is augmented with a concrete upgrade path to evolve towards an ultimate volume observatory by additional units of increasingly larger masses. With a three-fold increase in exposure (defined as the product neutrino beam power $\times$ far detector target mass), CPV becomes accessible at $>3\sigma$~C.L. for 75\% of the $\delta_{CP}$ parameter space, assuming that all systematic errors can be controlled below the 5\% level. The LBNO far site at 2300~km from CERN could also represent the first step towards a Neutrino Factory project based on the decays of muons in the straight sections of a storage ring. Based on the expertise present at CERN and in European and in international research groups, and building upon the results of several years of EU-funded design studies, we are confident that the technology for the beam and detectors is sufficiently mature to allow for an early start to realizing the facility. We are calling on CERN to promptly support and engage in the prototyping of the near and far detector components, to investigate options for campaigns of detector performance characterization and calibration with test beams in the North Area, and engage in a collaborative effort with the LBNO Collaboration that should lead to a full engineering design of the CN2PY beam and to an LBNO Proposal by the end of 2014.

see paper for full list of authors; This Expression of Interest (EoI) describes the motivation for and the feasibility studies of a long baseline neutrino oscillation experiment (LBNO) with a new conventional neutrino beamline facility (CN2PY). The beam will be aimed at a next generation deep-underground neutrino observatory comprising a double phase liquid argon (LAr) detector and a magnetized iron calorimeter, located at the Pyhäsalmi (Finland) mine at a distance of 2300~km. The double phase LAr Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC) is known to provide excellent tracking and calorimetry performance that can outperform other techniques. An initial 20~kton LAr fiducial volume, as considered here, comparable to the fiducial mass of SuperKamiokande and NOvA, offers a new insight and an increase in sensitivity reach for many physics channels. A magnetized iron calorimeter with muon momentum and charge determination collects an independent neutrino sample, and serves as a tail catcher for CERN beam events occurring in the LAr target. The long baseline physics objectives comprise the precise investigation of all flavor oscillations ($\nu_\mu\rightarrow \nu_\mu$, $\nu_\mu\rightarrow \nu_\tau$, $\nu_\mu\rightarrow \nu_e$) with neutrinos and antineutrinos, exploiting the energy spectrum information of the oscillation probability ($L/E$ method) in appearance and disappearance modes, to provide unambiguous sensitivity to oscillation parameters, and a stringent test of the 3-generation mixing. The existence of CP-violation will be tested explicitly, which is different from simply extracting the $\delta_{CP}$ violating phase from global fits of all available data. With an exposure of $2.25\times 10^{20}$~p.o.t. from the SPS at 400~GeV, a conclusive determination ($>5\sigma$~C.L.) of the neutrino mass hierarchy is possible for \emph{any} value of $\delta_{CP}$. Although limited by statistics in the initial configuration, the $L/E$ method also yields a clean measurement of the CP-violating phase. With $1\times 10^{21}$~p.o.t., the existence of CP-violation (CPV) can be demonstrated at the 90\%C.L. for $\sim 60\%$ of the $\delta_{CP}$ parameter space. This CPV-sensitivity is achievable in $\sim$12~years at the upgraded SPS. It improves further with the increased exposure resulting from longer running periods and/or an increase in beam power and far detector mass. With the chosen location in the deepest mine in Europe at $-1440$~m ($\sim$4000~m.w.e.), the already very large initial target mass provides an unique opportunity to observe new rare phenomena, independently of the CERN beam events. In the GeV range, evidence for Grand Unified Theories (GUT) can be searched for with nucleon decay signals. From 100~MeV to tens of GeV, the collection of thousands of atmospheric electron and muon neutrinos with good energy resolution and particle identification over a very large range of energies (SubGeV and MultiGeV) improves our understanding of this source and yields information on subleading oscillation effects, which provide additional and complementary sensitivity to the oscillation phenomenology including $\theta_{13}$, matter effects and possibly the CP-phase. At high energy, it allows an identification with high statistical significance and a study of $\nu_\tau$ appearance in atmospheric events. Below 100~MeV, neutrinos from a new galactic supernova burst would be recorded with large statistics, addressing the astrophysics of the supernova and neutrino flavor oscillations through the SN and Earth matter. Neutrinos from relic supernovae could also be potentially detected, depending on their flux and prevailing backgrounds. LBNO can also potentially detect as-of-yet unknown sources of astrophysical neutrinos, like for instance those that could arise from annihilation processes of WIMP particles in astrophysical objects, and study their flavor composition. The plan described so far is augmented with a concrete upgrade path to evolve towards an ultimate volume observatory by additional units of increasingly larger masses. With a three-fold increase in exposure (defined as the product neutrino beam power $\times$ far detector target mass), CPV becomes accessible at $>3\sigma$~C.L. for 75\% of the $\delta_{CP}$ parameter space, assuming that all systematic errors can be controlled below the 5\% level. The LBNO far site at 2300~km from CERN could also represent the first step towards a Neutrino Factory project based on the decays of muons in the straight sections of a storage ring. Based on the expertise present at CERN and in European and in international research groups, and building upon the results of several years of EU-funded design studies, we are confident that the technology for the beam and detectors is sufficiently mature to allow for an early start to realizing the facility. We are calling on CERN to promptly support and engage in the prototyping of the near and far detector components, to investigate options for campaigns of detector performance characterization and calibration with test beams in the North Area, and engage in a collaborative effort with the LBNO Collaboration that should lead to a full engineering design of the CN2PY beam and to an LBNO Proposal by the end of 2014.

217 pages, 164 figures, LBNO-DEMO (CERN WA105) Collaboration; In June 2012, an Expression of Interest for a long-baseline experiment (LBNO) has been submitted to the CERN SPSC. LBNO considers three types of neutrino detector technologies: a double-phase liquid argon (LAr) TPC and a magnetised iron detector as far detectors. For the near detector, a high-pressure gas TPC embedded in a calorimeter and a magnet is the baseline design. A mandatory milestone is a concrete prototyping effort towards the envisioned large-scale detectors, and an accompanying campaign of measurements aimed at assessing the detector associated systematic errors. The proposed $6\times 6\times 6$m$^3$ DLAr is an industrial prototype of the design discussed in the EoI and scalable to 20 kton or 50~kton. It is to be constructed and operated in a controlled laboratory and surface environment with test beam access, such as the CERN North Area (NA). Its successful operation and full characterisation will be a fundamental milestone, likely opening the path to an underground deployment of larger detectors. The response of the DLAr demonstrator will be measured and understood with an unprecedented precision in a charged particle test beam (0.5-20 GeV/c). The exposure will certify the assumptions and calibrate the response of the detector, and allow to develop and to benchmark sophisticated reconstruction algorithms, such as those of 3-dimensional tracking, particle ID and energy flow in liquid argon. All these steps are fundamental for validating the correctness of the physics performance described in the LBNO EoI.