PSAT Reading Practice Question 304

Question: 304

Passage 1 is adapted from Clara Moskowitz, "Mysterious Neutrinos Get New Mass Estimate." Adapted with permission. Copyright ©2019 Scientific American, a division of Nature America, Inc. All rights reserved. Passage 2 is adapted from Davide Castelvecchi, "Physicists close in on elusive neutrino's mass." ?2019 by Springer Nature.
Passage 1
Neutrinos, some of nature's weirdest fundamental 
particles, are nearly massless—emphasis on nearly. 
They were predicted to be completely massless, 
Line but experiments roughly 20 years ago found they 
05surprisingly do have some mass. Just how much has 
remained a mystery. Now a new calculation based on 
cosmological observations places an upper limit on 
how heavy the lightest kind of neutrino can be. 
The new mass limit comes from a supercomputer 
10calculation that combined data on the distribution of 
galaxies throughout the universe, the remnants of the 
first light released after the big bang and supernova 
measurements that reflect the expansion rate of the 
cosmos. The analysis also used laboratory data on 
15neutrinos to arrive at an estimate of the maximum 
weight of the smallest one: 0.086 electron volt, or 0.000
00000000000000000000000000000000015 kilogram—
making it at least six million times lighter than an 
electron.
20"What they have done is really nice work," says 
Olga Mena of the Institute of Corpuscular Physics in 
Spain, who has worked on similar calculations. André 
de Gouvêa, a theoretical physicist at Northwestern 
University, says, "It's a slightly more detailed analysis
2525 of cosmological data than people had done before. It's 
quite a nice paper."
The estimate complements other efforts to weigh 
neutrinos that focus on laboratory experiments. 
For instance, a project called the Karlsruhe Tritium 
30Neutrino (KATRIN) experiment in Germany aims to 
measure neutrino mass by observing beta decays in 
which a neutron transforms into a proton by releasing 
a neutrino and an electron. By carefully measuring 
the energy of the electron, scientists can infer the 
35mass of the neutrino. In contrast to cosmology-
based estimates, which include uncertainties from 
assumptions about unknowns such as dark matter and 
dark energy, this kind of experiment is more direct. 
Ultimately, scientists must compare the results 
40from all these different methods. "Only by combing 
all the possible ways of measuring the neutrino mass 
will we have a finite and robust answer," Mena says. 
But if the estimates differ, some scientists say, all 
the better. "One thing that's exciting is: What if we 
45make a measurement from cosmology, and we get 
an answer that doesn't agree with particle physics 
measurements?" de Gouvêa says. "That would be 
indicative of the fact that there's something in this 
picture that's just wrong. Maybe there's something 
50wrong with our understanding of the early universe. 
Or maybe there's something unusual about the 
mechanism for neutrino masses, like the mass depends 
on where you are or when you make the measurement. 
It sounds crazy, but it's possible."
Passage 2
5555 An experiment in Germany has made the most 
precise measurement yet of the maximum mass of 
neutrinos — light subatomic particles that are so 
devilishly difficult to measure that physicists have only 
been able to estimate the upper limit of their mass. 
60The first results from the Karlsruhe Tritium 
Neutrino (KATRIN) experiment in southwestern 
Germany reveal that neutrinos weigh at most 
1.1 electronvolts (eV). This measurement is a 
two-fold improvement over previous upper-
65bound 65 measurements of 2 eV. Guido Drexlin, co-
spokesperson for the KATRIN collaboration, presented 
the results on 13 September at a conference in Toyama, 
Japan. 
KATRIN collected data over a few weeks of its 
70initial run in April and May. The detector monitored 
the nuclear decay of a heavy isotope of hydrogen 
called tritium. During this process, a neutron turns 
into a proton and emits an electron and a neutrino. 
KATRIN cannot detect the neutrinos directly. Instead, 
75it measures the range of energies of the electrons that 
shoot around inside a 23-metre-long, blimp-shaped 
chamber, which is the largest ultra-high-vacuum 
system in the world. This measurement reveals the 
range of energies of the unseen neutrinos, which in 
80turn reveals their mass. 
During the next five years, Drexlin's collaboration 
plans to make continuous improvements to KATRIN's 
sensitivity that could enable it to make an actual 
measurement of a neutrino's mass — or to narrow the 
85range of the estimate as far as the machine's sensitivity 
will allow. Cosmological observations suggest that the 
mass of neutrinos could be 0.1 eV or lighter.

The authors of Passage 1 and Passage 2 would most likely agree that

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