Physics
https://hdl.handle.net/2144/1009
Department of Physics2021-09-21T17:39:30ZNMR relaxation in the spin-1 Heisenberg chain
https://hdl.handle.net/2144/42818
NMR relaxation in the spin-1 Heisenberg chain
Capponi, Sylvain; Dupont, Maxime; Sandvik, Anders W.; Sengupta, Pinaki
We consider the isotropic S=1 Heisenberg chain with a finite Haldane gap Δ and use state-of-the-art numerical techniques to investigate its dynamical properties at finite temperature, focusing on the nuclear spin-lattice relaxation rate 1/T1 measured in nuclear magnetic resonance (NMR) experiments, for instance. In particular, we analyze the contributions from modes with momenta close to q≈0 and q≈π as a function of temperature. At high-temperature we observe spin diffusion, while at low-temperature we argue that a simple activated behavior 1/T1∝exp(−Δ/T) can be observed only at temperatures much smaller than the gap Δ.
2019-09-09T00:00:00ZHilbert space fragmentation and Ashkin-Teller criticality in fluctuation coupled Ising models
https://hdl.handle.net/2144/42817
Hilbert space fragmentation and Ashkin-Teller criticality in fluctuation coupled Ising models
Patil, Pranay; Sandvik, Anders W.
We discuss the effects of exponential fragmentation of the Hilbert space on phase transitions in the context of coupled ferromagnetic Ising models in arbitrary dimension with special emphasis on the one-dimensional case. We show that the dynamics generated by quantum fluctuations is bounded within spatial partitions of the system and weak mixing of these partitions caused by global transverse fields leads to a zero temperature phase with ordering in the local product of both Ising copies but no long-range order in either species. This leads to a natural connection with the Ashkin-Teller universality class for general lattices. We confirm this for the periodic chain using quantum Monte Carlo simulations. We also point out that our treatment provides an explanation for pseudo-first-order behavior seen in the Binder cumulants of the classical frustrated J1−J2 Ising model and the q=4 Potts model in two dimensions.
2020-01-31T00:00:00ZMonte Carlo renormalization flows in the space of relevant and irrelevant operators: application to three-dimensional clock models
https://hdl.handle.net/2144/42816
Monte Carlo renormalization flows in the space of relevant and irrelevant operators: application to three-dimensional clock models
Shao, Hui; Guo, Wenan; Sandvik, Anders W.
We study renormalization group flows in a space of observables computed by Monte Carlo simulations. As an example, we consider three-dimensional clock models, i.e., the XY spin model perturbed by a Z_{q} symmetric anisotropy field. For q=4, 5, 6, a scaling function with two relevant arguments describes all stages of the complex renormalization flow at the critical point and in the ordered phase, including the crossover from the U(1) Nambu-Goldstone fixed point to the ultimate Z_{q} symmetry-breaking fixed point. We expect our method to be useful in the context of quantum-critical points with inherent dangerously irrelevant operators that cannot be tuned away microscopically but whose renormalization flows can be analyzed as we do here for the clock models.
2020-02-28T00:00:00ZBose-Einstein condensation of deconfined spinons in two dimensions
https://hdl.handle.net/2144/42815
Bose-Einstein condensation of deconfined spinons in two dimensions
Iaizzi, Adam; Scammell, Harley D.; Sushkov, Oleg P.; Sandvik, Anders W.
The transition between the Néel antiferromagnet and the valence-bond solid state in two dimensions has become a paradigmatic example of deconfined quantum criticality, a non-Landau transition characterized by fractionalized excitations (spinons). We consider an extension of this scenario whereby the deconfined spinons are subject to a magnetic field. The primary purpose is to identify the exotic scenario of a Bose-Einstein condensate of spinons. We employ quantum Monte Carlo simulations of the J−Q model with a magnetic field, and we perform a quantum field theoretic analysis of the magnetic field and temperature dependence of thermodynamic quantities. The combined analysis provides evidence for Bose-Einstein condensation of spinons and also demonstrates an extended temperature regime in which the system is best described as a gas of spinons interacting with an emergent gauge field.
2020-03-11T00:00:00ZScaling and diabatic effects in quantum annealing with a D-Wave device
https://hdl.handle.net/2144/42814
Scaling and diabatic effects in quantum annealing with a D-Wave device
Weinberg, Phillip; Tylutki, Marek; Rönkkö, Jami M.; Westerholm, Jan; Åström, Jan A.; Manninen, Pekka; Törmä, Päivi; Sandvik, Anders W.
We discuss quantum annealing of the two-dimensional transverse-field Ising model on a D-Wave device, encoded on L×L lattices with L≤32. Analyzing the residual energy and deviation from maximal magnetization in the final classical state, we find an optimal L dependent annealing rate v for which the two quantities are minimized. The results are well described by a phenomenological model with two powers of v and L-dependent prefactors to describe the competing effects of reduced quantum fluctuations (for which we see evidence of the Kibble-Zurek mechanism) and increasing noise impact when v is lowered. The same scaling form also describes results of numerical solutions of a transverse-field Ising model with the spins coupled to noise sources. We explain why the optimal annealing time is much longer than the coherence time of the individual qubits.
2020-03-06T00:00:00ZComment on “Gapless spin liquid ground state of the spin- 12 J1−J2 Heisenberg model on square lattices”
https://hdl.handle.net/2144/42813
Comment on “Gapless spin liquid ground state of the spin- 12 J1−J2 Heisenberg model on square lattices”
Zhao, Bowen; Takahashi, Jun; Sandvik, Anders W.
Liu et al. [Phys. Rev. B 98, 241109 (2018)] used Monte Carlo sampling of the physical degrees of freedom of a projected entangled pair state type wave function for the S=1/2 frustrated J1−J2 Heisenberg model on the square lattice and found a nonmagnetic state argued to be a gapless spin liquid when the coupling ratio g=J2/J1 is in the range g∈[0.42,0.6]. Here we show that their definition of the order parameter for another candidate ground state within this coupling window—a spontaneously dimerized state—is problematic. The order parameter as defined will not detect dimer order when lattice symmeties are broken due to open boundaries or asymmetries originating from the calculation itself. Thus, a dimerized phase for some range of g cannot be excluded (and is likely based on several other recent works).
2020-04-09T00:00:00ZExistence of a spectral gap in the Affleck-Kennedy-Lieb-Tasaki model on the hexagonal lattice
https://hdl.handle.net/2144/42812
Existence of a spectral gap in the Affleck-Kennedy-Lieb-Tasaki model on the hexagonal lattice
Lemm, Marius; Sandvik, Anders W.; Wang, Ling
The S=1 Affleck-Kennedy-Lieb-Tasaki (AKLT) quantum spin chain was the first rigorous example of an isotropic spin system in the Haldane phase. The conjecture that the S=3/2 AKLT model on the hexagonal lattice is also in a gapped phase has remained open, despite being a fundamental problem of ongoing relevance to condensed-matter physics and quantum information theory. Here we confirm this conjecture by demonstrating the size-independent lower bound Δ>0.006 on the spectral gap of the hexagonal model with periodic boundary conditions in the thermodynamic limit. Our approach consists of two steps combining mathematical physics and high-precision computational physics. We first prove a mathematical finite-size criterion which gives an analytical, size-independent bound on the spectral gap if the gap of a particular cut-out subsystem of 36 spins exceeds a certain threshold value. Then we verify the finite-size criterion numerically by performing state-of-the-art DMRG calculations on the subsystem.
2020-05-01T00:00:00ZQuantum phases of SrCu₂(BO₃)₂ from high-pressure thermodynamics
https://hdl.handle.net/2144/42811
Quantum phases of SrCu₂(BO₃)₂ from high-pressure thermodynamics
Guo, Jing; Sun, Guangyu; Zhao, Bowen; Wang, Ling; Hong, Wenshan; Sidorov, Vladimir A.; Ma, Nvsen; Wu, Qi; Li, Shiliang; Meng, Zi Yang; Sandvik, Anders W.; Sun, Liling
We report heat capacity measurements of SrCu₂(BO₃)₂ under high pressure along with simulations of relevant quantum spin models and map out the (P,T) phase diagram of the material. We find a first-order quantum phase transition between the low-pressure quantum dimer paramagnet and a phase with signatures of a plaquette-singlet state below T=2 K. At higher pressures, we observe a transition into a previously unknown antiferromagnetic state below 4 K. Our findings can be explained within the two-dimensional Shastry-Sutherland quantum spin model supplemented by weak interlayer couplings. The possibility to tune SrCu₂(BO₃)₂ between the plaquette-singlet and antiferromagnetic states opens opportunities for experimental tests of quantum field theories and lattice models involving fractionalized excitations, emergent symmetries, and gauge fluctuations.
2020-05-22T00:00:00ZQuantum-critical scaling properties of the two-dimensional random-singlet state
https://hdl.handle.net/2144/42809
Quantum-critical scaling properties of the two-dimensional random-singlet state
Liu, Lu; Guo, Wenan; Sandvik, Anders W.
Using quantum Monte Carlo simulations, we study effects of disorder on the S=1/2 Heisenberg model with exchange constant J on the square lattice supplemented by multispin interactions Q. It was found recently [L. Liu et al., Phys. Rev. X 8, 041040 (2018)] that the ground state of this J−Q model with random couplings undergoes a quantum phase transition from the Néel antiferromagnetic state into a randomness-induced spin-liquid-like state that is a close analog to the well known random-singlet (RS) state of the Heisenberg chain with random couplings. This 2D RS state arises from a spontaneously symmetry-broken fourfold degenerate columnar valence-bond solid that is broken up by the disorder into finite domains, with spinons localized at topological defects. The interacting spinons form a critical collective many-body state without magnetic long range order but with the mean spin-spin correlations decaying with distance r as r−2, as in the one-dimensional RS state. The dynamic exponent z≥2, varying continuously with the model parameters. In this work, we further investigate the properties of the RS state in the J−Q model with random Q couplings. We study the temperature dependence of the specific heat and various susceptibilities for large enough systems to reach the thermodynamic limit. We also analyze the size dependence of the critical magnetic order parameter and its susceptibility in the ground state. For all these quantities, we find consistency with the conventional quantum-critical scaling laws when the condition implied by the r−2 form of the spin correlations is imposed. In particular, all the different quantities can be explained by the same value of the dynamic exponent z at fixed model parameters. We argue that the RS state identified in the J−Q model corresponds to a generic renormalization group fixed point that can be reached in many quantum magnets with random couplings and that it has already been observed experimentally.
2020-08-31T00:00:00ZValence-bond solids, vestigial order, and emergent SO(5) symmetry in a two-dimensional quantum magnet
https://hdl.handle.net/2144/42808
Valence-bond solids, vestigial order, and emergent SO(5) symmetry in a two-dimensional quantum magnet
Takahashi, Jun; Sandvik, Anders W.
We introduce a quantum spin-1/2 model with many-body correlated Heisenberg-type interactions on the two-dimensional square lattice, designed so that the system can host a fourfold degenerate plaquette valence-bond solid (PVBS) ground state that spontaneously breaks Z4 symmetry. The system is sign-problem free and amenable to large-scale quantum Monte Carlo simulations, thus allowing us to carry out a detailed study of the quantum phase transition between the standard Néel antiferromagnetic (AFM) and PVBS states. We find a first-order transition, in contrast to previously studied continuous transitions from the AFM phase into a columnar valence-bond solid (CVBS) phase. The theory of deconfined quantum criticality predicts generic continuous AFM-CVBS and AFM-PVBS transitions, and, in one version of the theory, the two critical order parameters transform under SO(5) symmetry. Emergent SO(5) symmetry has indeed been observed in studies of the AFM-CVBS transition, and here we show that the first-order AFM-PVBS transition also exhibits SO(5) symmetry at the transition point. Such unexpected symmetry of the coexistence state, which implies a lack of energy barriers between the coexisting phases, has recently been observed at other first-order transitions, but the case presented here is the first example with SO(5) symmetry. The extended symmetry may indicate that the transition is connected to a deconfined critical point. We also discuss the first-order transition in the context of a recent proposal of spinons with fracton properties in the PVBS state, concluding that the fracton scenario is unlikely. Furthermore, we discover a novel type of eightfold degenerate VBS phase, arising when the PVBS state breaks a remaining Z2 symmetry. This second phase transition, which is continuous, implies that the PVBS phase can be regarded as an intermediate “vestigial” phase, a concept recently introduced to describe multistage phase transitions involving a continuous symmetry. Here we construct a six-dimensional order parameter and also introduce a general graph-theoretic approach to describe the two-stage discrete symmetry breaking. We discuss different ways of breaking the symmetries in one or two stages at zero and finite temperatures. In the latter case, we observe fluctuation-induced first-order transitions, which are hallmarks of vestigial phase transitions. We also mention possible connections of the AFM-PVBS transition to the SO(5) theory of high-T_c superconductivity.
Tunable deconfined quantum criticality and interplay of different valence-bond solid phases
https://hdl.handle.net/2144/42807
Tunable deconfined quantum criticality and interplay of different valence-bond solid phases
Zhao, Bowen; Takahashi, Jun; Sandvik, Anders W.
We use quantum Monte Carlo simulations to study an S = 1/2 spin model with competing multi-spin interactions. We find a quantum phase transition between a columnar valence-bond solid (cVBS) and a Néel antiferromagnet (AFM), as in the scenario of deconfined quantum-critical points, as well as a transition between the AFM and a staggered valence-bond solid (sVBS). By continuously varying a parameter, the sVBS–AFM and AFM–cVBS boundaries merge into a direct sVBS–cVBS transition. Unlike previous models with putative deconfined AFM–cVBS transitions, e.g., the standard J–Q model, in our extended J–Q model with competing cVBS and sVBS inducing terms the transition can be tuned from continuous to first-order. We find the expected emergent U(1) symmetry of the microscopically Z4 symmetric cVBS order parameter when the transition is continuous. In contrast, when the transition changes to first-order, the clock-like Z4 fluctuations are absent and there is no emergent higher symmetry. We argue that the confined spinons in the sVBS phase are fracton-like. We also present results for an SU(3) symmetric model with a similar phase diagram. The new family of models can serve as a useful tool for further investigating open questions related to deconfined quantum criticality and its associated emergent symmetries.
2020-05-01T00:00:00ZConsistent scaling exponents at the deconfined quantum-critical point
https://hdl.handle.net/2144/42806
Consistent scaling exponents at the deconfined quantum-critical point
Sandvik, Anders W.; Zhao, Bowen
We report a quantum Monte Carlo study of the phase transition between antiferromagnetic and valence-bond solid ground states in the square-lattice S = 1/2 J–Q model. The critical correlation function of the Q terms gives a scaling dimension corresponding to the value ν = 0.455 ± 0.002 of the correlation-length exponent. This value agrees with previous (less precise) results from conventional methods, e.g., finite-size scaling of the near-critical order parameters. We also study the Q-derivatives of the Binder cumulants of the order parameters for L2 lattices with L up to 448. The slope grows as L1/ν with a value of ν consistent with the scaling dimension of the Q term. There are no indications of runaway flow to a first-order phase transition. The mutually consistent estimates of ν provide compelling support for a continuous deconfined quantum-critical point.
2020-05-01T00:00:00ZMulticritical deconfined quantum criticality and Lifshitz point of a helical valence-bond phase
https://hdl.handle.net/2144/42805
Multicritical deconfined quantum criticality and Lifshitz point of a helical valence-bond phase
Zhao, Bowen; Takahashi, Jun; Sandvik, Anders W.
The S=1/2 square-lattice J-Q model hosts a deconfined quantum phase transition between antiferromagnetic and dimerized (valence-bond solid) ground states. We here study two deformations of this model-a term projecting staggered singlets, as well as a modulation of the J terms forming alternating "staircases" of strong and weak couplings. The first deformation preserves all lattice symmetries. Using quantum Monte Carlo simulations, we show that it nevertheless introduces a second relevant field, likely by producing topological defects. The second deformation induces helical valence-bond order. Thus, we identify the deconfined quantum critical point as a multicritical Lifshitz point-the end point of the helical phase and also the end point of a line of first-order transitions. The helical-antiferromagnetic transitions form a line of generic deconfined quantum-critical points. These findings extend the scope of deconfined quantum criticality and resolve a previously inconsistent critical-exponent bound from the conformal-bootstrap method.
2020-12-18T00:00:00ZExtreme suppression of antiferromagnetic order and critical scaling in a two-dimensional random quantum magnet
https://hdl.handle.net/2144/42804
Extreme suppression of antiferromagnetic order and critical scaling in a two-dimensional random quantum magnet
Hong, Wenshan; Liu, Lu; Liu, Chang; Ma, Xiaoyan; Koda, Akihiro; Li, Xin; Song, Jianming; Yang, Wenyun; Yang, Jinbo; Cheng, Peng; Zhang, Hongxia; Bao, Wei; Ma, Xiaobai; Chen, Dongfeng; Sun, Kai; Guo, Wenan; Luo, Huiqian; Sandvik, Anders W.; Li, Shiliang
Sr_2CuTeO_6 is a square-lattice Néel antiferromagnet with superexchange between first-neighbor S=1/2 Cu spins mediated by plaquette centered Te ions. Substituting Te by W, the affected impurity plaquettes have predominantly second-neighbor interactions, thus causing local magnetic frustration. Here we report a study of Sr_2CuTe_1-xW_xO_6 using neutron diffraction and μSR techniques, showing that the Néel order vanishes already at x=0.025±0.005. We explain this extreme order suppression using a two-dimensional Heisenberg spin model, demonstrating that a W-type impurity induces a deformation of the order parameter that decays with distance as 1/r^2 at temperature T=0. The associated logarithmic singularity leads to loss of order for any x>0. Order for small x>0 and T>0 is induced by weak interplane couplings. In the nonmagnetic phase of Sr_2CuTe_1-x W_x O_6, the μSR relaxation rate exhibits quantum critical scaling with a large dynamic exponent, z≈3, consistent with a random-singlet state.
2021-01-22T00:00:00ZUnconventional U(1) to Zq crossover in quantum and classical q -state clock models
https://hdl.handle.net/2144/42803
Unconventional U(1) to Zq crossover in quantum and classical q -state clock models
Patil, Pranay; Shao, Hui; Sandvik, Anders W.
We consider two-dimensional q-state quantum clock models with quantum fluctuations connecting states with all-to-all clock transitions with different choices for the matrix elements. We study the quantum phase transitions in these models using quantum Monte Carlo simulations and finite-size scaling, with the aim of characterizing the crossover from emergent U(1) symmetry at the transition (for q≥4) to Zq symmetry of the ordered state. We also study classical three-dimensional clock models with spatial anisotropy corresponding to the space-time anisotropy of the quantum systems. The U(1) to Zq symmetry crossover in all these systems is governed by a so-called dangerously irrelevant operator. We specifically study q=5 and q=6 models with different forms of the quantum fluctuations and different anisotropies in the classical models. In all cases, we find the expected classical XY critical exponents and scaling dimensions yq of the clock fields. However, the initial weak violation of the U(1) symmetry in the ordered phase, characterized by a Zq symmetric order parameter ϕq, scales in an unexpected way. As a function of the system size (length) L, close to the critical temperature ϕq∝Lp, where the known value of the exponent is p=2 in the classical isotropic clock model. In contrast, for strongly anisotropic classical models and the quantum models, we find p=3. For weakly anisotropic classical models, we observe a crossover from p=2 to p=3 scaling. The exponent p directly impacts the exponent ν′ governing the divergence of the U(1) to Zq crossover length scale ξ′ in the thermodynamic limit, according to the relationship ν′=ν(1+|yq|/p), where ν is the conventional correlation length exponent. We present a phenomenological argument for p=3 based on an anomalous renormalization of the clock field in the presence of anisotropy, possibly as a consequence of topological (vortex) line defects. Thus, our study points to an intriguing interplay between conventional and dangerously irrelevant perturbations, which may also affect other quantum systems with emergent symmetries.
2021-02-10T00:00:00ZFractional and composite excitations of antiferromagnetic quantum spin trimer chains
https://hdl.handle.net/2144/42802
Fractional and composite excitations of antiferromagnetic quantum spin trimer chains
Cheng, Jun-Qing; Li, Jun; Xiong, Zijian; Wu, Han-Qing; Sandvik, Anders W.; Yao, Dao-Xin
Using Lanczos exact diagonalization, stochastic analytic continuation of quantum Monte Carlo data, and perturbation theory, we investigate the dynamic spin structure factor S(q, 𝜔) of the S=1/2 antiferromagnetic Heisenberg trimer chain. We systematically study the evolution of the spectrum by varying the ratio g=J_2/J_1 of the intertrimer and intratrimer coupling strengths and interpret the observed features using analytical and numerical calculations with the trimer eigenstates. The doublet ground states of the trimers form effective interacting S=1/2 degrees of freedom described by a Heisenberg chain with coupling J_eff=(4/9)J_2. Therefore, the conventional two-spinon continuum of width ∝ J_1 when g =1 evolves into to a similar continuum of width ∝ J_2 in the reduced Brillouin zone when g ⟶ 0. The high-energy modes (at 𝜔 ∝ J_1) for g ≈ 0.5 can be understood as weakly dispersing propagating internal trimer excitations (which we term doublons and quartons), and these fractionalize with increasing g to form the conventional spinon continuum when g is increased toward 1. The coexistence of two kinds of emergent spinon branches for intermediate values of g give rise to interesting spectral signatures, especially at g ≈ 0.7 where the gap between the low-energy spinon branch and the high energy band of mixed doublons, quartons, and spinons closes. These features should be observable in inelastic neutron scattering experiments if a quasi-one-dimensional quantum magnet with the linear trimer structure and J_2 < J_1 can be identified. We suggest that finding such materials would be useful, enabling detailed studies of coexisting exotic excitations and their interplay within a relatively simple theoretical framework.
2020-01-01T00:00:00ZDeconfined quantum criticality in spin-1/2 chains with long-range interactions
https://hdl.handle.net/2144/42801
Deconfined quantum criticality in spin-1/2 chains with long-range interactions
Yang, Sibin; Yao, Dao-Xin; Sandvik, Anders W.
We study spin-1/2 chains with long-range power-law decaying unfrustrated (bipartite) Heisenberg exchange J_r ∝ r^-𝛂 and multi-spin interactions Q favoring a valence-bond solid (VBS) ground state. Employing quantum Monte Carlo techniques and Lanczos diagonalization, we analyze order parameters and excited-state level crossings to characterize quantum states and phase transitions in the (𝛂,Q) plane. For weak Q and sufficiently slowly decaying Heisenberg interactions (small 𝛂), the system has a long-range-ordered antiferromagnetic (AFM) ground state, and upon increasing 𝛂 there is a continuous transition into a quasi long-range ordered (QLRO) critical state of the type in the standard Heisenberg chain. For rapidly decaying long-range interactions, there is transition between QLRO and VBS ground states of the same kind as in the frustrated J_1-J_2 Heisenberg chain. Our most important finding is a direct continuous quantum phase transition between the AFM and VBS states - a close analogy to the 2D deconfined quantum-critical point. In previous 1D analogies the ordered phases both have gapped fractional excitations, and the critical point is a conventional Luttinger-Liquid. In our model the excitations fractionalize upon transitioning from the AFM state, changing from spin waves to deconfined spinons. We extract critical exponents at the AFM-VBS transition and use order-parameter distributions to study emergent symmetries. We find emergent O(4) symmetry of the O(3) AFM and scalar VBS order parameters. Thus, the order parameter fluctuations exhibit the covariance of a uniaxially deformed O(4) sphere (an "elliptical" symmetry). This unusual quantum phase transition does not yet have any known field theory description, and our detailed results can serve to guide its construction. We discuss possible experimental realizations.
2020-01-01T00:00:00ZThe mini-CAPTAIN liquid argon time projection chamber
https://hdl.handle.net/2144/42788
The mini-CAPTAIN liquid argon time projection chamber
Grant, Christopher
2020-01-01T00:00:00ZCurrent status and future prospects of the SNO+ experiment
https://hdl.handle.net/2144/42787
Current status and future prospects of the SNO+ experiment
Andringa, S.; Arushanova, E.; Asahi, S.; Askins, M.; Auty, D.J.; Back, A.R.; Barnard, Z.; Barros, N.; Beier, E.W.; Bialek, A.; Biller, S.D.; Blucher, E.; Bonventre, R.; Braid, D.; Caden, E.; Callaghan, E.; Caravaca, J.; Carvalho, J.; Cavalli, L.; Chauhan, D.; Chen, M.; Chkvorets, O.; Clark, K.; Cleveland, B.; Coulter, I.T.; Cressy, D.; Dai, X..; Darrach, C.; Davis-Purcell, B.; Deen, R.; Depatie, M.M.; Descamps, F.; Di Lodovico, F.; Duhaime, N.; Duncan, F.; Dunger, J.; Falk, E.; Fatemighomi, N.; Ford, R.; Gorel, P.; Grant, Christopher; Grullon, S.; Guillian, E.; Hallin, A.L.; Hallman, D.; Hans, S.; Hartnell, J.; Harvey, P.; Hedayatipour, M.; Heintzelman, W.J.; Helmer, R.L.; Hreljac, B.; Hu, J.; Iida, T.; Jackson, C.M.; Jelley, N.A.; Jillings, C.; Jones, C.; Jones, P.G.; Kamdin, K.; Kaptanoglu, T.; Kaspar, J.; Keener, P.; Khaghani, P.; Kippenbrock, L.; Klein, J.R.; Knapik, R.; Kofron, J.N.; Kormos, L.L.; Korte, S.; Kraus, C.; Krauss, C.B.; Labe, K.; Lam, I.; Lan, C.; Land, B.J.; Langrock, S.; LaTorre, A.; Lawson, I.; Lefeuvre, G.M.; Leming, E.J.; Lidgard, J.; Liu, X.; Liu, Y.; Lozza, V.; Maguire, S.; Maio, A.; Majumdar, K.; Manecki, S.; Maneira, J.; Marzec, E.; Mastbaum, A.; McCauley, N.; McDonald, A.B.; McMillan, J.E.; Mekarski, P.; Miller, C.; Mohan, Y.; Mony, E.; Mottram, M.J.; Novikov, V.; O’Keeffe, H.M.; O’Sullivan, E.; Orebi Gann, G.D.; Parnell, M.J.; Peeters, S.J.M.; Pershing, T.; Petriw, Z.; Prior, G.; Prouty, J.C.; Quirk, S.; Reichold, A.; Robertson, A.; Rose, J.; Rosero, R.; Rost, P.M.; Rumleskie, J.; Schumaker, M.A.; Schwendener, M.H.; Scislowski, D.; Secrest, J.; Seddighin, M.; Segui, L.; Seibert, S.; Shantz, T.; Shokair, T.M.; Sibley, L.; Sinclair, J.R.; Singh, K.; Skensved, P.; Sörensen, A.; Sonley, T.; Stainforth, R.; Strait, M.; Stringer, M.I.; Svoboda, R.; Tatar, J.; Tian, L.; Tolich, N.; Tseng, J.; Tseung, H.W.C.; Van Berg, R.; Vázquez-Jáuregui, E.; Virtue, C.; von Krosigk, B.; Walker, J.M.G.; Walker, M.; Wasalski, O.; Waterfield, J.; White, R.F.; Wilson, J.R.; Winchester, T.J.; Wright, A.; Yeh, M.; Zhao, T.; Zuber, K.
SNO+ is a large liquid scintillator-based experiment located 2 km underground at SNOLAB, Sudbury, Canada. It reuses the Sudbury Neutrino Observatory detector, consisting of a 12 m diameter acrylic vessel which will be filled with about 780 tonnes of ultra-pure liquid scintillator. Designed as a multipurpose neutrino experiment, the primary goal of SNO+ is a search for the neutrinoless double-beta decay (0νββ) of ^130Te. In Phase I, the detector will be loaded with 0.3% natural tellurium, corresponding to nearly 800 kg of ^130Te, with an expected effective Majorana neutrino mass sensitivity in the region of 55–133 meV, just above the inverted mass hierarchy. Recently, the possibility of deploying up to ten times more natural tellurium has been investigated, which would enable SNO+ to achieve sensitivity deep into the parameter space for the inverted neutrino mass hierarchy in the future. Additionally, SNO+ aims to measure reactor antineutrino oscillations, low energy solar neutrinos, and geoneutrinos, to be sensitive to supernova neutrinos, and to search for exotic physics. A first phase with the detector filled with water will begin soon, with the scintillator phase expected to start after a few months of water data taking. The 0νββ Phase I is foreseen for 2017.
2016-01-01T00:00:00ZOpportunities with decay-at-rest neutrinos from decay-In-flight neutrino beams
https://hdl.handle.net/2144/42786
Opportunities with decay-at-rest neutrinos from decay-In-flight neutrino beams
Grant, C.; Littlejohn, B.R.
Neutrino beam facilities, like spallation neutron facilities, produce copious quantities of neutrinos from the decay at rest of mesons and muons. The viability of decay-in-flight neutrino beams as sites for decay-at-rest neutrino studies has been investigated by calculating expected low-energy neutrino fluxes from the existing Fermilab NuMI beam facility. Decay-at-rest neutrino production in NuMI is found to be roughly equivalent per megawatt to that of spallation facilities, and is concentrated in the facility's target hall and beam stop regions. Interaction rates in 5 and 60 ton liquid argon detectors at a variety of existing and hypothetical locations along the beamline are found to be comparable to the largest existing decay-at-rest datasets for some channels. The physics implications and experimental challenges of such a measurement are discussed, along with prospects for measurements at targeted facilities along a future Fermilab long-baseline neutrino beam.
2015-10-28T00:00:00Z