A. Psallidas

The High Luminosity phase of the Large Hadron Collider will deliver 10 times more integrated luminosity than the existing collider, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry. As part of its upgrade program, the Compact Muon Solenoid collaboration is designing a high-granularity calorimeter (HGCAL) to replace the existing endcap calorimeters. It will feature unprecedented transverse and longitudinal readout and triggering segmentation for both electromagnetic and hadronic sections. The electromagnetic section and a large fraction of the hadronic section will be based on hexagonal silicon sensors of 0.5–1 cm2 cell size, with the remainder of the hadronic section being based on highly-segmented scintillators with silicon photomultiplier readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection. First hexagonal silicon modules, using the existing Skiroc2 front-end ASIC developed for CALICE, have been tested in beams at Fermilab and CERN in 2016. We present results from these tests, in terms of system stability, calibration with minimum-ionizing particles and resolution (energy, position and timing) for electrons, and the comparisons of these quantities with GEANT4-based simulation.

Neutrino oscillation experiments provide a unique window in exploring several new physics scenarios beyond the standard three flavour. One such scenario is quantum decoherence in neutrino oscillation which tends to destroy the interference pattern of neutrinos reaching the far detector from the source. In this work, we study the decoherence in neutrino oscillation in the context of the ESSnuSB experiment. We consider the energy-independent decoherence parameter and derive the analytical expressions for P$_{\mu e}$ and P$_{\mu \mu}$ probabilities in vacuum. We have computed the capability of ESSnuSB to put bounds on the decoherence parameters namely, $\Gamma_{21}$ and $\Gamma_{32}$ and found that the constraints on $\Gamma_{21}$ are competitive compared to the DUNE bounds and better than the current T2K and MINOS ones. We have also investigated the impact of decoherence on the ESSnuSB measurement of the Dirac CP phase $\delta_{\rm CP}$ and concluded that it remains robust in the presence of new physics.

We explore the possibility of interpreting the solar and atmospheric neutrino data within the context of the Minimal Supersymmetric Standard Model augmented by a single U(1) anomalous family symmetry spontaneously broken by non-zero vacuum expectation values of a pair of singlet fields. The symmetry retains a dimension-five operator which provides Majorana masses for left-handed neutrino states. Assuming symmetric lepton mass matrices, the model predicts inverse hierarchical neutrino mass spectrum, theta_{13}=0 and large mixing while at the same time it provides acceptable mass matrices for the charged fermions.

A long optical base line spectrophotometer designed to measure light transmission in deep sea waters is described. The variable optical path length allows measurements without the need for absolute or external calibration. The spectrophotometer uses eight groups of uncollimated light sources emitting in the range 370–530 nm and was deployed at various depths at two locations in the Ionian Sea that are candidate sites for a future underwater neutrino telescope. Light transmission spectra at the two locations are presented and compared.

The long optical base transmissometer (LAMS—Long Arm Marine Spectrophotometer) constructed in 2008 by NESTOR group is described. The data of the recent water transparency measurements in the NESTOR site and in the Capo Passero site in the wavelength range 378–522 nm are presented

Calorimeters with silicon detectors have many unique features and are proposed for several world-leading experiments. We discuss the tests of the first three 18x18 cm$^2$ layers segmented into 1024 pixels of the technological prototype of the silicon-tungsten electromagnetic calorimeter for a future $e^+e^-$ collider. The tests have beem performed in November 2015 at CERN SPS beam line.

A novel type of resistive Micromegas combining a Bulk mesh and a resistive pad board is presented. Readout pads are covered by a thin insulating layer with a top resistive coating segmented into resistive pads. Readout and resistive pads are electrically connected by means of planar resistors embedded in the insulator, enabling fast clearance of the avalanche charge from the resistive surface. The maximum gas gain achieved by these resistive detectors is similar to that of non-resistive Micromegas. A possible saturation of the gain for large energy deposits in the gas was investigated by means of 55Fe quanta and electromagnetic showers in the 30–200 GeV energy range, but no significant deviation from a proportional response was found. With a suitable choice of the resistance, these detectors demonstrate negligible gain drop and no sparking up to X-ray fluxes of ∼ 1 MHz / mm2 which constitutes a major improvement over non-resistive Micromegas. Spark suppression was also verified in a hadron beam for prototypes with a pad resistance as low as 40 kΩ or above. Passive protections of the front-end electronics against sparks (diodes on a printed circuit board) are therefore not required for these resistive detectors.

We study D-brane inspired models with $U(3)\ifmmode\times\else\texttimes\fi{}U(2)\ifmmode\times\else\texttimes\fi{}U(1{)}^{N}$ gauge symmetry in the context of split supersymmetry. We consider configurations with one, two and three $(N=1,2,3)$ Abelian branes and derive all hypercharge embeddings which imply a realistic particle content. Then, we analyze the implications of split supersymmetry on the magnitude of the string scale, the gauge coupling evolution, the third family fermion mass relations and the gaugino masses. We consider gauge coupling relations which may arise in parallel as well as intersecting brane scenarios and classify the various models according to their predictions for the magnitude of the string scale and the low energy implications. In the parallel brane scenario where the $U(1)$ branes are superposed to $U(2)$ or $U(3)$ brane stacks, varying the split-SUSY scale in a wide range, we find three distinct cases of models predicting a high, intermediate and low string scale, ${M}_{S}\ensuremath{\sim}{10}^{16}\text{ }\text{ }\mathrm{GeV}$, ${M}_{S}\ensuremath{\sim}{10}^{7}\text{ }\text{ }\mathrm{GeV}$ and ${M}_{S}\ensuremath{\sim}{10}^{4}\text{ }\text{ }\mathrm{GeV}$, respectively. We further find that in the intermediate string scale model the low energy ratio ${m}_{b}/{m}_{\ensuremath{\tau}}$ is compatible with $b--\ensuremath{\tau}$ Yukawa unification at the string scale. Furthermore, we perform a similar analysis for arbitrary Abelian gauge coupling relations at ${M}_{S}$ corresponding to possible intersecting brane models. We find cases which predict a string scale of the order ${M}_{S}\ensuremath{\ge}{10}^{14}\text{ }\text{ }\mathrm{GeV}$ that accommodate a right-handed neutrino mass of the same order so that a seesaw type, light, left-handed neutrino component is obtained in the sub-eV range as required by experimental and cosmological data. Finally, a short discussion is devoted to the gaugino masses and the lifetime of the gluino.

Resistive micromegas is proposed as an active element for sampling calorimetry. Future linear collider experiments or the HL-LHC experiments can profit from those developments for Particle Flow Calorimetry. Micromegas possesses remarkable properties concerning gain stability, reduced ion feedback, response linearity, adaptable sensitive element granularity, fast response and high rate capability. Recent developments on Micromegas with a protective resistive layer present excellent results, resolving the problem of discharges caused by local high charge deposition, thanks to its RC-slowed charge evacuation. Higher resistivity though, may cause loss of the response linearity at high rates. We have scanned a wide range of resistivities and performed laboratory tests with X-rays that demonstrate excellent response linearity up to rates of (a few) times 10 MHz / cm 2 , with simultaneous mitigation of discharges. Beam test studies at SPS/CERN with hadrons have also shown a remarkable stability of the resistive Micromegas and low currents for rates up to 15 MHz / cm 2 . We present results from the aforementioned studies confronted with MC simulation

In this paper we study non-standard interactions mediated by a scalar field (SNSI) in the context of ESSnuSB experiment. In particular we study the capability of ESSnuSB to put bounds on the SNSI parameters and also study the impact of SNSI in the measurement of the leptonic CP phase $\delta_{\rm CP}$. Existence of SNSI 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 $\eta_{\mu\mu}$, $\eta_{\tau\tau}$ and $\eta_{\mu\tau}$ depend upon how $\Delta m^2_{31}$ is minimized in the theory. However, this is not the case when one tries to measure the impact of SNSI on $\delta_{\rm CP}$. 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 $\delta_{\rm CP}$.

A silicon-based fine granularity calorimeter is a potential technology for the future International Linear Collider ILC, the future circular collider CEPC, and is also the chosen technology for the upgraded CMS experiment of the Large Hadron Collider. Active silicon sensing pads are used as MIP counters and the standard calibration of the calorimeter uses weights based on the average energy loss, dEdx. In this work, the limitations of the dEdx calibration method in terms of energy linearity, scale and resolution are explored. In the case of a calorimeter with varying passive layer thickness as the one planned for CMS, the dEdx method leads to a significant constant term in the resolution function and a non-linearity of energy response. For these reasons, a method based on the calorimeter sampling fraction that exploits the per-event measured shower depth is presented and shown to deliver superior absolute energy scale, linearity and resolution. Calorimetric designs in which the back of the shower is sampled less, offer reduced cost without loss in performance. Therefore, a proper calibration as proposed here is crucial in obtaining the most cost- and performance-effective silicon-sampling calorimeter design.

Motivated by effective low energy models of string origin, we discuss the neutrino masses and mixing within the context of the Minimal Supersymmetric Standard Model supplemented by a U(1) anomalous family symmetry and additional Higgs singlet fields charged under this extra U(1). In particular, we interpret the solar and atmospheric neutrino data assuming that there are only three left-handed neutrinos which acquire Majorana masses via a lepton number violating dimension-five operator. We derive the general form of the charged lepton and neutrino mass matrices when two different pairs of singlet Higgs fields develop nonzero vacuum expectation values and show how the resulting neutrino textures are related to approximate lepton flavor symmetries. We perform a numerical analysis for one particular case and obtain solutions for masses and mixing angles, consistent with experimental data.

We discuss renormalization effects on neutrino masses and mixing angles in a supersymmetric string-inspired $\mathrm{SU}(4)\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(2{)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(2{)}_{R}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{X}$ model, with matter in fundamental and antisymmetric tensor representations and singlet Higgs fields charged under the anomalous $\mathrm{U}(1{)}_{X}$ family symmetry. The quark, lepton and neutrino Yukawa matrices are distinguished by different Clebsch-Gordan coefficients. The presence of a second $\mathrm{U}(1{)}_{X}$ breaking singlet with fractional charge allows a more realistic, hierarchical light neutrino mass spectrum with bi-large mixing. By numerical investigation we find a region in the model parameter space where the neutrino mass-squared differences and mixing angles at low energy are consistent with experimental data.

Abstract A requirement for neutrino telescope is the ability to resolve point sources of neutrinos. In order to understand its resolving power a way to perform absolute angular calibration with muons is required. Muons produced by cosmic rays in the atmosphere offer an abundant calibration source. By covering a surface vessel with 200 modules of 5 m 2 plastic scintillator a surface air shower array can be set up. Running this array in coincidence with a deep-sea km 3 size neutrino detector, where the coincidence is defined by the absolute clock timing stamp for each event, would allow absolute angular calibration to be performed. Monte Carlo results simulating the absolute angular calibration of the km 3 size neutrino detector will be presented. Future work and direction will be discussed.

To measure variations of zenith dependence of sedimentation/bio-fouling on the optical modules (OMs) as considered by the KM3NeT consortium in the deep sea, we have used a grid of photodiodes distributed inside the glass sphere to measure the light intensity of two light sources located outside the glass sphere on a fixed position. The method is described and the data collected during the last three years in depths from 3100 m down to 5100 m, in the southeast Ionian sea, at sites near Pylos, Peloponnese, Greece, are discussed.

In this thesis, the possibility of interpreting the solar and atmospheric neutrino data within the context of theoretical models is being explored. In particular, the implications of the Minimal Supersymmetric Standard Model augmented by a single U(1) anomalous family symmetry for neutrino masses and mixing angles are investigated. Motivated by the above results, the effect of introducing a proper second singlet pair is studied resulting to additional mass entries in the previous model. Also, renormalization effects on neutrino masses and mixing angles in a supersymmetric string-inspired SU(4)xSU(2)_LxSU(2)_RxU(1)_X model are discussed. Lastly, D-brane inspired models are studied with U(3)xU(2)xU(1)^N gauge symmetry in the context of split supersymmetry.

In this talk, we discuss the implications of the renormalization group equations for the neutrino masses and mixing angles in a supersymmetric string-inspired SU(4)×SU(2)L×SU(2)R×U(1)X model with matter in fundamental and antisymmetric tensor representations only.The quark, charged lepton and neutrino Yukawa matrices are distinguished by different Clebsch-Gordan coefficients due to contracting over SU(4) and SU(2)R indices.In order to permit for a more realistic, hierarchical light neutrino mass spectrum with bi-large mixing a second U (1)X breaking singlet with fractional charge is introduced.By numerical investigation we find a region in the model parameter space where the neutrino mass-squared differences and mixing angles at low energy are consistent with experimental data.

In this talk we discuss the implications of the Minimal Supersymmetric Standard Model augmented by a single U(1) anomalous family symmetry for neutrino masses and mixing angles. The left-handed neutrino states are provided with Majorana masses through a dimension-five operator in the absence of right handed neutrino components. Assuming symmetric lepton mass matrices, the model predicts inverse hierarchical neutrino mass spectrum, theta_13=0 and large mixing while at the same time it provides acceptable mass matrices for the charged fermions.