About

Andrea Pocar is a Professor and Department Head in the Department of Physics at the University of Massachusetts Amherst. He holds a Ph.D. from Princeton University obtained in 2003 and a Laurea from the University of Milan, Italy, earned in 1996. His research interests encompass particle and nuclear physics, with a focus on instrumentation related to neutrinos, dark matter, light detection, and radon background mitigation. Pocar is recognized for award-winning teaching and offers research opportunities and interdisciplinary programs within a diverse and inclusive community of excellence. His main office is located in the Department of Physics at 1126 Lederle Graduate Research Tower, University of Massachusetts Amherst.

Research topics

• Physics
• Nuclear physics
• Computer Science
• Particle physics
• Optics
• Atomic physics
• Artificial Intelligence
• Astrophysics
• Mathematics
• Mathematical analysis
• Materials science
• Engineering
• Quantum mechanics
• Chemistry
• Algorithm
• Electronic engineering

Selected publications

• Sensitivity of nEXO to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mmultiscripts> <mml:mrow> <mml:mi>Xe</mml:mi> </mml:mrow> <mml:mprescripts/> <mml:none/> <mml:mrow> <mml:mn>136</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:mrow> </mml:math> charged-current interactions: Background-free searches for solar neutrinos and fermionic dark matter

  Physical review. D/Physical review. D. · 2025-11-06 · 1 citations

  article

  We study the sensitivity of nEXO to solar neutrino charged-current interactions, ${\ensuremath{\nu}}_{e}+^{136}\mathrm{Xe}\ensuremath{\rightarrow}\phantom{\rule{0ex}{0ex}}{^{136}\mathrm{Cs}}^{*}+{e}^{\ensuremath{-}}$, as well as analogous interactions predicted by models of fermionic dark matter. Due to the recently observed low-lying isomeric states of $^{136}\mathrm{Cs}$, these interactions will create a time-delayed coincident signal observable in the scintillation channel. Here we develop a detailed Monte Carlo simulation of scintillation emission, propagation, and detection in the nEXO detector to model these signals under different assumptions about the timing resolution of the photosensor readout. We show this correlated signal can be used to achieve background discrimination on the order of ${10}^{\ensuremath{-}9}$, enabling nEXO to make background-free measurements of solar neutrinos above the reaction threshold of 0.668 MeV. We project that nEXO could measure the flux of neutrinos from the carbon-nitrogen-oxygen cycle with a statistical uncertainty of 25%, thus contributing a novel and competitive measurement toward addressing the solar metallicity problem. Additionally, nEXO could measure the mean energy of the $^{7}\mathrm{Be}$ neutrinos with a precision of $\ensuremath{\sigma}\ensuremath{\le}1.5\text{ }\text{ }\mathrm{keV}$ and could determine the survival probability of $^{7}\mathrm{Be}$ and pep solar ${\ensuremath{\nu}}_{e}$ with precision comparable to the state of the art. These quantities are sensitive to the Sun's core temperature and to nonstandard neutrino interactions, respectively. Furthermore, the strong background suppression would allow nEXO to search for charged-current interactions of fermionic dark matter in the mass range ${m}_{\ensuremath{\chi}}=0.668--7\text{ }\text{ }\mathrm{MeV}$ with a sensitivity up to three orders of magnitude better than current limits.

  PublisherDOI

• Review of neutron yield from ( <i>α</i> , <i>n</i> ) reactions: data, methods, and prospects

  Journal of Physics G Nuclear and Particle Physics · 2025-07-15 · 3 citations

  preprintOpen access

  Abstract Understanding the radiogenic neutron production rate from the ( α , n ) reaction is crucial in many areas of physics, including dark matter searches, neutrino studies, and nuclear astrophysics. In addition to its relevance for fundamental research, the ( α , n ) reaction also plays a significant role in nuclear energy technologies, for example by contributing to neutron production in subcritical systems using UO 2 , as well as in applications such as medical physics. This review examines the current state of ( α , n ) yield calculations and neutron spectra, describes the computational tools used for their estimation, and discusses the available cross-section data. We investigate the uncertainties affecting ( α , n ) yield estimations and propose strategies to enhance their accuracy. Furthermore, we highlight the need for new measurements of ( α , n ) cross-sections for a variety of relevant materials. Such measurements are key to improving neutron flux predictions and reducing uncertainties in sensitivity estimates for next-generation physics experiments operating in the keV–MeV range.

  PublisherDOI

• Sensitivity of nEXO to $^{136}$Xe Charged-Current Interactions: Background-free Searches for Solar Neutrinos and Fermionic Dark Matter

  ArXiv.org · 2025-06-27

  preprintOpen access

  We study the sensitivity of nEXO to solar neutrino charged-current interactions, $ν_e + ^{136}$Xe$\rightarrow ^{136}$Cs$^* + e^-$, as well as analogous interactions predicted by models of fermionic dark matter. Due to the recently observed low-lying isomeric states of $^{136}$Cs, these interactions will create a time-delayed coincident signal observable in the scintillation channel. Here we develop a detailed Monte Carlo of scintillation emission, propagation, and detection in the nEXO detector to model these signals under different assumptions about the timing resolution of the photosensor readout. We show this correlated signal can be used to achieve background discrimination on the order of $10^{-9}$, enabling nEXO to make background-free measurements of solar neutrinos above the reaction threshold of 0.668 MeV. We project that nEXO could measure the flux of CNO solar neutrinos with a statistical uncertainty of 25%, thus contributing a novel and competitive measurement towards addressing the solar metallicity problem. Additionally, nEXO could measure the mean energy of the $^7$Be neutrinos with a precision of $σ\leq 1.5$ keV and could determine the survival probability of $^{7}$Be and $pep$ solar $ν_e$ with precision comparable to state-of-the-art. These quantities are sensitive to the Sun's core temperature and to non-standard neutrino interactions, respectively. Furthermore, the strong background suppression would allow nEXO to search for for charged-current interactions of fermionic dark matter in the mass range $m_χ$ = $0.668$-$7$ MeV with a sensitivity up to three orders of magnitude better than current limits.

  PublisherOA PDFDOI

• Ultra-sensitive radon assay using an electrostatic chamber in a recirculating system

  Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment · 2025-08-01 · 2 citations

  articleOpen access

  Rare event searches such as neutrinoless double beta decay and Weakly Interacting Massive Particle detection require ultra-low background detectors. Radon contamination is a significant challenge for these experiments, which employ highly sensitive radon assay techniques to identify and select low-emission materials. This work presents the development of ultra-sensitive electrostatic chamber (ESC) instruments designed to measure radon emanation in a recirculating gas loop, for future lower background experiments. Unlike traditional methods that separate emanation and detection steps, this system allows continuous radon transport and detection. This is made possible with a custom-built recirculation pump. A Python-based analysis framework, PyDAn, was developed to process and fit time-dependent radon decay data. Radon emanation rates are given for various materials measured with this instrument. A radon source of known activity provides an absolute calibration, enabling statistically-limited minimal detectable activities of 20 μ Bq. These devices are powerful tools for screening materials in the development of low-background particle physics experiments.

  PublisherDOI

• Search for high energy 5.5 MeV solar axions with the complete Borexino dataset

  The European Physical Journal C · 2025-10-21

  articleOpen access

  Abstract A search for solar axions and axion-like particles produced in the $$p+d\rightarrow ^3\textrm{He}+A~(5.5 ~\textrm{MeV})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>p</mml:mi> <mml:mo>+</mml:mo> <mml:mi>d</mml:mi> <mml:msup> <mml:mo>→</mml:mo> <mml:mn>3</mml:mn> </mml:msup> <mml:mtext>He</mml:mtext> <mml:mo>+</mml:mo> <mml:mi>A</mml:mi> <mml:mspace/> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>5.5</mml:mn> <mml:mspace/> <mml:mtext>MeV</mml:mtext> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> reaction was performed using the complete dataset of the Borexino detector (3995 days of measurement live-time). The following interaction processes have been considered: axion decay into two photons $$(\textrm{A}\rightarrow 2\gamma )$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mtext>A</mml:mtext> <mml:mo>→</mml:mo> <mml:mn>2</mml:mn> <mml:mi>γ</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> , inverse Primakoff conversion on nuclei $$(\textrm{A}+Z\rightarrow \gamma +Z$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mtext>A</mml:mtext> <mml:mo>+</mml:mo> <mml:mi>Z</mml:mi> <mml:mo>→</mml:mo> <mml:mi>γ</mml:mi> <mml:mo>+</mml:mo> <mml:mi>Z</mml:mi> </mml:mrow> </mml:math> ), the Compton conversion of axions to photons $$(\textrm{A}+e\rightarrow e+\gamma )$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mtext>A</mml:mtext> <mml:mo>+</mml:mo> <mml:mi>e</mml:mi> <mml:mo>→</mml:mo> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> <mml:mi>γ</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> and the axio-electric effect $$(\textrm{A}+e+Z\rightarrow e+Z$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mtext>A</mml:mtext> <mml:mo>+</mml:mo> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> <mml:mi>Z</mml:mi> <mml:mo>→</mml:mo> <mml:mi>e</mml:mi> <mml:mo>+</mml:mo> <mml:mi>Z</mml:mi> </mml:mrow> </mml:math> ). Model-independent limits on product of axion–photon ( $$g_{A\gamma }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>g</mml:mi> <mml:mrow> <mml:mi>A</mml:mi> <mml:mi>γ</mml:mi> </mml:mrow> </mml:msub> </mml:math> ), axion–electron ( $$g_{Ae}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>g</mml:mi> <mml:mrow> <mml:mi>Ae</mml:mi> </mml:mrow> </mml:msub> </mml:math> ), and isovector axion–nucleon ( $$g_{3AN}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>g</mml:mi> <mml:mrow> <mml:mn>3</mml:mn> <mml:mi>A</mml:mi> <mml:mi>N</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) couplings are obtained: $$|g_{A\gamma }\times g_{3AN}| \le 2.3\times 10^{-11} \textrm{GeV}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mrow> <mml:mo>|</mml:mo> </mml:mrow> <mml:msub> <mml:mi>g</mml:mi> <mml:mrow> <mml:mi>A</mml:mi> <mml:mi>γ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>×</mml:mo> <mml:msub> <mml:mi>g</mml:mi> <mml:mrow> <mml:mn>3</mml:mn> <mml:mi>A</mml:mi> <mml:mi>N</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>|</mml:mo> <mml:mo>≤</mml:mo> <mml:mn>2.3</mml:mn> <mml:mo>×</mml:mo> </mml:mrow> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>11</mml:mn> </mml:mrow> </mml:msup> <mml:msup> <mml:mtext>GeV</mml:mtext> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> and $$|g_{Ae}\times g_{3AN}| \le 1.9\times 10^{-13}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">

  PublisherOA PDFDOI

• Latest results from EXO-200

  AIP conference proceedings · 2025-01-01

  article1st authorCorresponding
  PublisherDOI

• Fermionic sub-GeV Dark Matter from evaporating Primordial Black Holes at DarkSide-50

  ArXiv.org · 2025-05-19

  preprintOpen access

  We present a search for boosted dark matter from Primordial Black Holes (PBH) evaporation using the DarkSide-50 ionization-signal-only dataset corresponding to the experiment's ($12202\pm180$) ${\rm kg\: d}$ exposure. We focus on evaporation of PBHs with masses in the range [$10^{14},\,10^{16}$] g producing Dirac fermionic dark matter particles with sub-GeV kinetic energy. These relativistic particles, with energies up to hundreds of MeV, can generate detectable signals for masses below $\mathcal{O}(100)$ MeV. The absence of a signal enables setting complementary limits to those derived from cosmological observations and direct detection searches for cosmic ray-boosted dark matter.

  PublisherOA PDFDOI

• Ultra-low-background physics: lessons from BOREXINO and future steps

  2025-03-20

  articleOpen access

  The Borexino experiment concluded the data acquisition at the end of 2021 and among the solar neutrino experiments it has been the only one capable of reconstructing the position and the energy on an event-by-event base, with an energy threshold of 150 keV, thanks to its ultra-high radio-purity. The experimental techniques and analysis methods that allowed Borexino to reach such unprecedented levels of radio-purity are now a standard and the legacy that Borexino leaves to the next low energy neutrinos and rare event searching experiments. This contribution is aimed to present the methods and the main achievements of the Borexino and to summarize the broad experimental effort presently in progress in the field of ultra-low background physics to further improve the sensitivity with massive underground detectors and new techniques.

  PublisherOA PDFDOI

• Ultra-pure Nickel for Structural Components of Low-Radioactivity Instruments

  ArXiv.org · 2025-08-11

  preprintOpen access

  International audience

  PublisherOA PDF

• Combined directional and spectral analysis of solar neutrinos from Carbon-Nitrogen-Oxygen fusion cycle with Borexino Experiment

  2024-01-28

  articleOpen access

  Borexino, placed at LNGS in Italy, was a 280-ton liquid scintillator detector that took data from May 2007 to October 2021. Thanks to its unprecedented radio-purity, the real time spectroscopic measurement of solar neutrinos from both the \textit{pp}-chain and Carbon-Nitrogen-Oxygen (CNO) fusion cycle of the Sun has been performed. Borexino also reported the first directional measurement of sub-MeV $^7$Be solar neutrinos with the Phase-I period (May 2007-May 2010) using a novel technique called Correlated and Integrated Directionality (CID), exploiting the sub-dominant and directional Cherenkov photons detected at early times. For the first time, we provide the CNO solar neutrinos measurement without using an independent constraint on $^{210}$Bi background rate by exploiting the CID technique on the complete Borexino detector live time dataset. This article presents the complete analysis strategy and the latest results on CNO solar neutrinos obtained by using the CID technique in Borexino. In addition, we also present the most precise CNO measurement obtained by Borexino using a spectral fit on the Phase-III dataset as used in 2022 analysis, where the novel CID result is now applied as an additional constraint.

  PublisherOA PDFDOI

Recent grants

• A Search for Neutrino-less Double Beta Decay with nEXO

  NSF · $750k · 2018–2022

• A Search for Weakly-Interacting Particle Dark Matter with DarkSide

  NSF · $285k · 2016–2019

• Neutrino-Less Double Beta Decay with EXO-200 and EXO

  NSF · $609k · 2012–2016

• Collaborative Research: Solar Neutrino Science with Borexino: The Quest for CNO Neutrinos

  NSF · $92k · 2019–2023

• Particle Astrophysics with Neutrinos and Weakly Interacting Dark Matter: Borexino and DarkSide

  NSF · $576k · 2012–2016

Frequent coauthors

• D. Franco

  University of Chicago

  734 shared

• C. Galbiati

  Gran Sasso Science Institute

  409 shared

• Y. Suvorov

  390 shared

• M. Pallavicini

  383 shared

• A. Sotnikov

  382 shared

• A. Razeto

  366 shared

• F. Ortica

  University of Chinese Academy of Sciences

  364 shared

• A. Romani

  360 shared

Labs

• Pocar GroupPI

Education

• PhD, Physics

  Princeton University

  2003

• Laurea, Physics

  Università degli Studi di Milano

  1996