PSAT 8/9 Reading Practice Test 7

Questions 1-8 refer to the following information.

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.