ID #40; arXiv:2404.17559 amann16.iitr@gmail.com Investigating Quantum Decoherence in ν-Oscillation at ESSnuSB Experiment Author: Aman Gupta 1,2; Presenter: Monojit Ghosh 3 on behalf of the ESSnuSB collaboration 1Saha Institute of Nuclear Physics,Kolkata, India, 2HBNI,Mumbai, India,3Ruđer Bošković Institute,Zagreb, Croatia Introduction •Neutrino oscillation is a quantum mechanical phenomenon that arises due to the coherent superposition of neutrino mass states. However, if neutrino as a quantum system is coupled to an environment, the coherence between two or more propagating states may be lost leading to the suppression of flavour oscillations. •Such type of environmentally induced quantum decoherence (QD) in neutrino states might emerge from quantum gravity effects or space-time “foam” which acts as dissipative sources and can modify the ν-oscillation probability in various ways [1]. QD: Formalism The time evolution of neutrinos in an open quantum system is given by ∂ρ(t) ∂t = −i[H, ρ(t)] + D[ρ(t)] , (1) where H is the neutrino Hamilto- nian which can be written as H = 1 2E   U                    0 0 0 0 ∆m2 21 0 0 0 ∆m2 31                    U†   + VCC                    1 0 0 0 0 0 0 0 0                    . (2) The effect of decoherence is given by the dissipator matrix D which on imposing relevant physical con- ditions can be parametrized as D = −diag(Γ21, Γ21, 0, Γ31, Γ31, Γ32, Γ32, 0) . (3) The solution to the Eq.1 is given by ρα ij(x) = ˜U∗ αi ˜Uαje−(Γij+i ˜∆ij)x (4) and the oscillation probabilities in the presence of decoherence read as P(να →νβ) = Tr  ρα(0)ρβ(x)   (5) Here, ˜U is the modified PMNS ma- trix in matter and ˜∆ij = ∆˜m2 ijL 4E , with ∆˜m2 ij being the mass squared differences in matter. •L = 360 km, Water Cherenkov detector of fiducial volume 538 kt and 5 years run-time of neutrino + 5 years of antineutrino [2]. Oscillation Probability including Decoherence P(να →νβ) = δαβ −2 X i>j Re " ˜U∗ αi ˜Uβi ˜Uβj ˜U∗ βj #  1 −cos  2 ˜∆ij  e−ΓijL  + 2 X i>j Im " ˜U∗ αk ˜Uβk ˜Uβj ˜U∗ βj # sin  2 ˜∆ij  e−ΓijL , QD induces terms similar to damping phenomena of the form e−ΓijL in the oscillation probability. Fig.: Effect of Γ21 and Γ32 on the appearance probability for the ESSnuSB. •The Pµe probability is mostly affected by Γ21 in comparison to Γ32. •The effect of Γ21 is significant when δCP is −90◦. Important Analytical Formulae For maximal CPV, the relevant contributing terms for Γ21 and Γ32 are |P CP−odd µe | ∝|2α∆31(Γ21L −2 sin2 ∆31) −Γ21L sin 2∆31| . |P CP−odd µe | ∝|Γ32L cos 2∆31 + 2 sin2 ∆31| . For δCP = 0, 180◦, expression for CPV precision is given by: ∆δCP ∝ 1 |2α∆31(Γ21L −2 sin2 ∆31) −Γ21L sin 2∆31| ; 1 |α∆31Γ32L cos 2∆31 + 2α∆31 sin2 ∆31| . On the other hand, for maximal CP violation, we obtain ∆δCP ∝ 1 |Γ21L(cos 2∆31 + cos 2θ12) + 2α∆31 sin 2∆31| ; 1 |α∆31(1 −Γ32L) sin ∆31| . Bounds on Γ21 and Γ32 Other experimental bounds at 90% C.L. are [3, 4] Γ32 = Γ21 < 9.4 × 10−24 GeV [MINOS/MINOS+], Γ21 < 1.2 × 10−23 GeV [DUNE], Γ32 < 4.7 × 10−24 GeV [DUNE] . CPV Sensitivity & Precision 24.0 23.5 23.0 22.5 22.0 21.5 21.0 log10 0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 2 (CPV) solid: true CP = + 90° dashed: true CP = 90° 21 when 32 = 0 32 when 21 = 0 21 = 32 For small Γ21, the sensitivity first slightly decreases and when the de- coherence term becomes dominant, the relevant probability increases along with Γ21, improving the sen- sitivity. 24.0 23.5 23.0 22.5 22.0 21.5 21.0 log10 0 1 2 3 4 5 6 7 8 CP[in deg.] solid: 21 when 32 = 0 dashed: 32 when 21 = 0 dot dashed: 32 = 21 true CP = 0° true CP = 180° 24.0 23.5 23.0 22.5 22.0 21.5 21.0 log10 0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 CP[in deg.] solid: 21 when 32 = 0 dashed: 32 when 21 = 0 dot dashed: 32 = 21 true CP = + 90° true CP = 90° 2.24 cm Correlations Key Takeaways •For the first time, we explore the sensitivity of ESSnuSB to const