**NuMI Commissioning Report**

**February 17, 2005**

# Introduction

The Project Execution Plan for the Neutrinos at the Main Injector (NuMI)
Project specifies a set of technical goals for project commissioning. In
accordance with the Project Execution Plan, these goals must be
satisfied for Critical Decision 4 (CD-4), the formal approval to start
operations. Table 1.1 summarizes the commissioning goals for NuMI.

  ----------------------- ----------------------- -----------------------
  **Parameter**           **Measurement**         **Commissioning Goal**

  Proton intensity in     Toroid (or equivalent)  Greater than 1 × 10^12^
  target hall             beam intensity monitor  120 GeV protons per
                          at entrance to the      spill
                          target hall             

  Beam alignment          Transverse              Proton direction
                          distributions of the    established to within 1
                          proton beam and         mr of the known
                          secondary beams         direction to the far
                                                  detector in the Soudan
                                                  mine

  Neutrino beam energy    Near Detector event     low energy, 2-4 GeV
                          energy                  

  Cosmic ray muons        Near Detector data read Majority of the 153
  detected in the MINOS   out through DAQ system  Near Detector planes
  Near Detector                                   sensitive to muons

  Near Detector neutrino  Charged-current event   Observe neutrinos
  flux                    rate in 1.5 ton         produced in the Near
                          fiducial region         Detector by the NuMI
                                                  beam

  Cosmic ray muons and    Far Detector data read  Majority of the 484
  atmospheric neutrinos   out through DAQ system  planes of the Far
  detected in each of the                         Detector sensitive to
  two MINOS Far Detector                          muons and atmospheric
  Supermodules                                    neutrinos
  ----------------------- ----------------------- -----------------------

Table 1.1 NuMI technical commissioning goals

The following sections address each of these goals. The section will
explicitly describe the measurements that define the successful
attainment of the goal and provide documentation that the goal has in
fact been attained.

# Proton Intensity in the Target Hall

The Fermilab Main Injector accelerates protons to a momentum of 120
GeV/c. A set of "kicker" magnets then extracts the 120 GeV protons and
sends them into the NuMI beamline, through which they are transported to
the NuMI target. The NuMI commissioning goal is to achieve a proton
intensity of 1 × 10^12^ protons per spill at the target.

## Beam Toroids

The intensity of the beam is measured by a series of devices in the Main
Injector and in the NuMI beamline. A DC Current Transformer (DCCT) with
the device name I:BEAMM in the Main Injector measures the intensity of
the Main Injector beam. The primary beam intensity in the NuMI line is
measured in two places by bench-calibrated toroid monitors. The first
(E:TOR101D) is in the MI60 region, 25 meters downstream of the kicker
magnets. The second (E:TORTGTD) is 20 meters upstream of the target.
Ensuring that the beam is cleanly extracted from the Main Injector and
transported through these monitors checks the calibration. Figure 2.1
shows beam intensity per spill in these three devices from Friday
January 22, 20:00 to 20:30 hours. A beam spill occurred every 2 minutes.
The intensity ranged from zero to 3 × 10^12^ protons/spill. Differences
in the measurements are due to minor mis-calibration of the NuMI
toroids.

![](media/image1.png){width="5.8597222222222225in"
height="4.6930555555555555in"}

Figure 2.1 Beam intensity in the Main Injector (I:IBEAMM) and in the
NuMI\
beamline (E:TOR101D, E:TORTGTD) for a 30 minute period during the
January\
test run.

Figure 2.2 shows the readout from the downstream toroid in the NuMI
beamline during the commissioning run. The vertical scale shows protons
on target × 10^12^. This goal is exceeded throughout most of the run.

![](media/image2.png){width="5.439583333333333in"
height="4.102083333333334in"}

Figure 2.2 Readout from toroid device E:TORTGT during the NuMI
commissioning run.

## Summary

The toroid and equivalent devices in the Main Injector and the NuMI
beamline have measured beam intensities during the NuMI commissioning
run. The proton intensity exceeds the commissioning goal of 1 × 10^12^
protons per spill at 120 GeV.

# Beam Alignment

The commissioning goal for alignment of the NuMI beam is to establish
the direction of the primary proton beam to within 1 milliradian (mr) of
the known direction to the MINOS far detector in the Soudan mine.
Measurements with the Global Positioning System (GPS) locate a network
of survey monuments on the surface of the Earth. The Fermilab alignment
group extended this network below ground at both sites, installing
survey monuments in the Pre-target, Target, and Absorber Hall regions
and at Soudan. Quality Assurance measurements taken during the NuMI
tunnel construction have shown the tunnel to be aimed at the mine to
within 0.015 mr. To meet the commissioning goal, the NuMI proton beam
must be aligned with the NuMI tunnel to within an acceptable tolerance.

A set of beam profile monitors in the NuMI pre-target area measures the
proton beam position as it enters the target hall. These monitors are
aligned relative to the NuMI survey monuments. The aiming of the proton
beam is measured by the distributions in monitors for the primary and
secondary beams. Hadron monitor measurements provide the most direct
measure of the proton beam alignment. Muon monitor measurements provide
additional confirmation.

## Beam Profile Monitors

The beam profile is monitored by segmented foil Secondary Emission
Monitors (SEMs), which measure the horizontal or vertical position of
the beam with a precision of 50 μm or better. The SEMs are aligned
relative to the NuMI facility survey monuments. Figure 3.3 shows the
readout from the SEM profile monitors as measured during the NuMI
commissioning run on January 21, 2005. They show clean extraction and
transport of protons through the NuMI beamline with the beam centered at
the entrance to the target hall.

![](media/image3.png){width="4.340972222222222in"
height="3.4868055555555557in"}

Figure 3.3 SEM readouts from the NuMI beam commissioning run.

## The NuMI Hadron Monitor

The NuMI hadron monitor is a 7 × 7 array of parallel plate ionization
chambers, which is installed in the absorber stack between the
downstream end of the decay pipe and the upstream face aluminum absorber
core. The hadron monitor is designed to verify the alignment of the NuMI
proton beam. It is located 732.1 m downstream of the pre-target SEMs and
is aligned relative to the Absorber Hall survey monuments. The initial
beam pulses were directed into the NuMI beamline, with no target in
place, the horns de-energized, and the decay pipe evacuated, thus
leaving as clear a path as possible for the primary beam protons to
reach the monitor. The relative count rates in the ionization chamber
plates show the positioning of the NuMI proton beam.

### Calibration and Alignment of the Hadron Monitor

The relative pixel calibration was established to within 3% using
radioactive sources, with the initial variation at the 10% level before
correction. The hadron monitor is installed in the absorber stack
through a 6-inch slot and is positioned on a set of support rails. The
rails were installed and surveyed relative to the Absorber cavern
alignment network prior to the construction of the hadron absorber core.
Measurements of the installed hadron monitor show that the nominal beam
center is aligned with the center ionization chamber.

### Beam Position at the Hadron Monitor

Figure 3.4 and Figure 3.5 depict the readout from the NuMI hadron
monitor during the commissioning run in horizontal and vertical views.
The horizontal axes of the figures show the position, in inches, of the
individual ion chambers. The horizontal axis represents the charge
readout during the beam pulse. The distance from the MTGT monitor to the
hadron monitor is 732.1 m. Pulse-to-pulse measurements in the SEMs and
the hadron monitor have verified the accuracy of the proton beam angle
within the tunnel to .035 mr.

![](media/image4.png){width="5.76875in" height="3.08125in"}

Figure 3.4 *x*-position of hadron monitor readout from beam
commissioning.

![](media/image5.png){width="6.0in" height="3.207638888888889in"}

Figure 3.5 *y*-position of hadron monitor readout from beam
commissioning.

## The NuMI Muon Monitors

The NuMI muon monitors comprise three sets of 9 × 9 arrays of ion
chambers, each array covering 2m × 2m. These devices, named E:MMA1D,
E:MMA2D and E:MMA3D in ACNET, are located in the first, second and third
muon alcoves downstream of the hadron absorber. Their function is to
monitor the NuMI beam by measuring the position and relative intensity
of the muon flux as it passes through successive amounts of material.

The commissioning run included a target scan with the beam, during which
the muon monitors read out data as the beam moved from the target center
to the baffle. The baffle is 2.5 meters upstream of the target, so that
when the proton beam strikes the baffle, the horns focus a higher-energy
spectrum of pions than when the beam hits the target. The focusing of
higher-energy pions results in a higher-energy spectrum of muons. The
energy that a muon requires to penetrate the rock to reach the first,
second and third muon alcoves is approximately 4 GeV, 9 GeV and 17 GeV,
respectively. Figure 3.6 and Figure 3.7 demonstrate the ability to aim
and align the NuMI beam. Figure 3.6 shows the horizontal and vertical
projections of the three muon monitors superimposed when the proton beam
is centered on the target. The distribution is centered, with relatively
low readings in the two downstream monitors. In Figure 3.7, the proton
beam is deliberately striking the baffle. The distribution is
off-center, reflecting the fact that the beam is not on target. The
number of muons reaching alcoves 2 and 3, relative to those in alcove 1,
is significantly higher, indicating a higher-energy muon spectrum as
expected.

![](media/image6.png){width="6.0in" height="1.8597222222222223in"}

Figure 3.6 Muon monitor readout during the NuMI commissioning run with
the beam focused on target. The left histogram shows x position in
inches; the right histogram shows *y* position in inches.

![](media/image7.png){width="5.992361111111111in" height="2.00625in"}

Figure 3.7 Muon monitor readout during the NuMI commissioning run with
the beam deliberately focused on the baffle. The left histogram shows x
position in inches; the right histogram shows *y* position in inches.

## Summary

Data from the commissioning run show the primary and secondary beam
monitors to perform well. Combining the errors of the NuMI tunnel
alignment with the Soudan mine (.015 mr) and the proton beam with the
NuMI tunnel (.035 mr), we find that the proton beam is aligned with the
Soudan mine to within .038 mr, well within the commissioning goal. Thus,
this commissioning goal has been achieved.

# Cosmic Ray Muons in the MINOS Near Detector

The installation of the MINOS Near Detector began in March 2004 and was
completed in August 2004. Initial testing of the Near Detector
Electronics and DAQ system took place during this time, using natural
radioactivity and dark current from the phototubes. As the construction
progressed, the detector planes were used to reconstruct muon tracks
from cosmic rays and the completed detector now has a substantial sample
of cosmic ray data. The commissioning goal requires that the majority of
the 153 active planes in the Near Detector be sensitive to muons. Data
read out through the near detector Data Acquisition (DAQ) system are
used here to demonstrate that this has been achieved.

## Near Detector Plane Sensitivity

Figure 4.8 depicts the arrangement of scintillator planes in the two
sections of the Near Detector. In the calorimeter section all steel
planes are covered by scintillator; every fifth is fully covered, while
the intervening planes are partially covered. In the spectrometer
section every fifth steel plane is fully covered by scintillator, while
the intervening planes are uninstrumented steel. This configuration
dictates the way in which events in the Near Detector are triggered.

![](media/image8.png){width="2.747916666666667in"
height="2.0229166666666667in"}![](media/image9.png){width="2.873611111111111in"
height="2.1381944444444443in"}

Figure 4.8 Schematic illustration of the calorimeter (left) and
spectrometer (right) planes of the MINOS Near Detector.

### Near Detector Trigger

All of the data presented in this section were recorded with the "10/12"
trigger or the "10 activity" trigger. The "10/12" trigger reads out the
detector when 10 out of 12 consecutive planes register a "hit". The "10
activity" trigger reads out the detector when 10 detector planes
anywhere register a "hit". By focusing on events that extend over 10 or
more planes, these triggers target the penetrating muons.

### Near Detector Plane Occupancy

Figure 4.9 and Figure 4.10 show a pair of occupancy plots for the
reconstructed cosmic muons in the MINOS Near Detector. The color
gradations indicate the number of reconstructed muon tracks passing
through each module or strip for a selected set of data runs. Figure 4.9
depicts the number of reconstructed tracks that pass through each
scintillator module. Figure 4.10 depicts the number of reconstructed
tracks that pass through each scintillator strip. The occupancy plots
show that not only are all of detector planes functioning, but all of
the modules and most of the scintillator strips are functioning as well.
The densely-occupied region at the lower left is the fiducial region of
the calorimeter section, including fully- and partially-instrumented
planes. The vertical lines extending above this region represent the
additional modules of the fully-instrumented planes (one in every five).
The right-hand side of the plot represents the spectrometer region.

![](media/image10.png){width="5.579861111111111in" height="3.31875in"}

Figure 4.9 Cosmic ray muon occupancy (module *vs.* plane) for the MINOS
Near Detector.

![](media/image11.png){width="5.544444444444444in"
height="3.254166666666667in"}

Figure 4.10 Cosmic ray muon occupancy (strip *vs.* plane) for the MINOS
Near Detector.

These plots verify that the detector, electronics, DAQ and
reconstruction software are functioning and that all active planes are
sensitive to muons. The downstream spectrometer region is sparsely
occupied; that is expected and understood. The spectrometer region has a
4-fold plex, namely 4 different scintillator strips are read out by the
same electronics channel. This results in four "mirror" images in each
view of the spectrometer that cannot by themselves reconstruct the
actual event. Thus the reconstruction software reconstructs
3-dimensional tracks only if they start in the calorimeter region, which
is not multiplexed. The Near Detector is, of course, not optimized to
detect nearly-vertical cosmic rays. Muon tracks from beam neutrinos lie
closer to the detector axis and, in general, are easier to follow from
the calorimeter into the spectrometer.

## Cosmic Ray Muon Distributions

Figure 4.11 depicts the event display for a typical cosmic ray muon in
the MINOS Near Detector. The top panel shows the transverse position of
hit strips in the *u* view versus the *z* position of the plane. The
middle panel shows the same for the *v* view. The relative sizes of the
signal from each hit in the event are shown in the histograms along the
top and sides of the *uz* and *vz* views. The lower left panel is the
*xy* projection of the track. The lower right graph shows the time for
each digit along the track versus its y-position.

![](media/image12.png){width="3.886111111111111in"
height="3.6256944444444446in"}

Figure 4.11 Event display of a typical cosmic ray muon in the Near
Detector.

Figure 4.12 shows the zenith angle distribution of cosmic ray data for
tracks with a length greater than 20 planes. The probability that these
tracks are muons, as opposed to detector noise, is extremely high. The
zenith angle distribution is in agreement with expectations: very few
horizontal muons and none from directly above. The latter effect is due
to the software trigger used to record these events and the track length
criterion.

![](media/image13.png){width="4.059722222222222in"
height="2.7527777777777778in"}

Figure 4.12 Zenith angle distribution of cosmic ray muons in the near
detector.

The azimuth angle distribution again reflects the trigger used and the
detector geometry: Muons traversing the detector along the *x* direction
won't satisfy the trigger criterion. Again the results agree very well
with expectations.

![](media/image14.png){width="4.001388888888889in"
height="2.7090277777777776in"}

Figure 4.13 Azimuthal distribution of cosmic ray muons in the near
detector.

## Summary

The data presented in this section demonstrate that the MINOS Near
Detector is capable of observing cosmic ray muon events and reading them
out through the MINOS DAQ system. They also show that all of the
detector's active planes are sensitive to muons. Thus, this
commissioning goal has been achieved.

# Cosmic Ray Muons & Atmospheric Neutrinos in the MINOS Far Detector

The MINOS far detector has taken cosmic ray data since September 2002,
when the first supermodule was completed and magnetized. Construction of
the second supermodule was still in progress and was completed in July
2003. The full magnetized detector has taken data since that time. The
far detector routinely observes muons produced by cosmic ray
interactions in the atmosphere. The commissioning goal requires that the
majority of the Far Detector's 484 planes are sensitive to muons and
atmospheric neutrinos.

Muons and neutrino events are observed in both supermodules of the Far
Detector. Data read out through the Far Detector DAQ system is used to
reconstruct these events, which include cosmic ray muons and neutrinos.
The latter are observed in both upward-going muon events and contained
events.

## Far Detector Plane Sensitivity

Each instrumented plane of the Far Detector contains 8 scintillator
modules. Each module contains 192 scintillator strips.

![](media/image15.png){width="2.876388888888889in"
height="2.089583333333333in"}
![](media/image16.png){width="2.876388888888889in"
height="2.0861111111111112in"}

Figure 5.14 Occupancy plots from muon tracks in the MINOS far detector.

Figure 5.14 shows the occupancy of tracks by module and by strip for
both supermodules of the far detector. The two plots on the left are for
supermodule 1; those on the right are for supermodule 2. The horizontal
axis on all plots represents plane number. On the upper plots, the
vertical axis represents the scintillator module number. On the lower
plots, the vertical axis represents the scintillator strip number. The
color gradations indicate the number of reconstructed muon tracks
passing through each module or strip for a selected set of data runs.
The red bands in the upper plots represent the largest modules (2 and
7), which have the greatest number of tracks, while the smallest modules
(1 and 8), have the fewest. This result is just as one would expect.
These plots not only demonstrate that all of the instrumented Far
Detector planes are sensitive to muons, but also that all of the modules
and most of the strips are sensitive to them as well.

## Observation of Muons

Figure 5.15 and Figure 5.16 show the geometrical distribution of
observed muons. The criteria for identifying an event as containing a
muon require that a reconstructed track traverse at least 20 planes in
the detector and that the track length be at least 2 meters.

![](media/image17.png){width="4.292361111111111in"
height="2.9034722222222222in"}

Figure 5.15 Zenith angle distribution of cosmic ray muons in the MINOS
far detector.

Figure 5.15 shows the zenith angle \[cos(θ)\] distribution. The sharp
drop off of the distribution near cos(θ) = 1 reflects the fact that the
muons coming from directly above the detector will not pass the cuts on
the number of planes crossed and track length, due to low acceptance for
those angles. The distribution also falls with increasing zenith angle,
as the amount of rock between the detector and the surface increases
rapidly for values of cos(θ) near the horizon. Only the most energetic
muons can penetrate the overburden at these angles.

![](media/image18.png){width="4.313194444444444in" height="2.95625in"}

Figure 5.16 Azimuthal distribution of cosmic ray muons in the MINOS far
detector.

Figure 5.16 shows the azimuthal distribution of the cosmic ray muons.
The azimuthal angle is defined by φ = 0° due north and φ = 90° due east.
Since the detector is not aligned north-south, but rather on a line
pointing toward Fermilab, the muons with values of φ \< 60° have had
360° added to the azimuth for this plot. This is to make the muons from
the north be in a contiguous region, 240° \< φ \< 420°. Similarly, muons
coming from the south have 60° \< φ \< 240°. More muons come from the
south than the north because there is more rock to the north.

## Upward-Going Muons from Atmospheric Neutrinos

The far detector has observed muons produced by neutrino interactions in
the rock surrounding the detector. These muons are uniquely identifiable
when they come from below the detector, where the amount of rock between
the detector and the surface is so great that cosmic ray muons cannot
penetrate it. MINOS is able to observe neutrino-induced muons coming
from zenith angles -1 \< cos(θ) \< 0.1 (the flat overburden at the
Soudan site allows neutrino-induced muons coming from above the horizon
to be observed).

### Detector Timing Calibration

A good timing calibration is essential for identifying neutrino-induced
muons coming from below the horizon, as these events are selected based
on the timing of the hits along the tracks. The 1/β distribution of the
muons, where β is the ratio of the measured muon velocity to the speed
of light, provides a quality check of the timing calibration.

Figure 5.17 shows the 1/β distribution for events satisfying the muon
selection criteria. The downward-going muons have 1/β \~ 1 and
upward-going candidates have 1/β \~ -1. Gaussian distributions fitted to
the upward- and downward-going muons have widths of 0.05, indicating
timing calibrations that are more than adequate to distinguish upward-
from downward-going muons.

![](media/image19.png){width="3.39375in" height="2.8645833333333335in"}

Figure 5.17 Timing distributions (1/β) for muons in the MINOS far
detector.

### Observation of Upward-Going Muons

The magnetic field in the far detector allows the charge sign of the
particles interacting in it to be determined. Figure 5.18 shows the
event display for an upward going μ^+^. The top panel shows the
transverse position of hit strips in the *u* view versus the *z*
position of the plane for both supermodules. The middle panel shows the
same for the *v* view. The relative sizes of the signal from each hit in
the event are shown in the histograms along the top and sides of the
*uz* and *vz* views. The lower left panel is the *xy* projection of the
track. The lower right graph shows the time for each digit along the
track versus its *y*-position, as the *y* direction increases away from
the center of the Earth. This muon is clearly upward-going since the
time of the hits along the track increase with increasing values of *y*.
The lower right hand legend gives a summary of the event information.

![](media/image20.png){width="3.9805555555555556in" height="3.25625in"}

Figure 5.18 Event display for an upward-going muon in the MINOS far
detector.

## Contained Neutrino Events

As the name implies, a fully-contained event is one in which the charged
particles observed do not enter or exit the detector. This is an
indicator that they have been produced by a neutrino interaction at the
endpoint of the event. Figure 5.19 and Figure 5.20 show sample events of
this type. These were chosen from a set of 37 candidate events derived
from 2.52 kiloton-years of cosmic ray data in the far detector.

![](media/image21.png){width="3.935416666666667in"
height="3.8118055555555554in"}

Figure 5.19 Event display for a contained neutrino event in Supermodule
1.

![](media/image22.png){width="4.021527777777778in" height="3.8875in"}

Figure 5.20 Event display for a contained neutrino event in Supermodule
2.

These events, along with other candidate neutrino events in the data
set, demonstrate that both supermodules of the MINOS far detector are
sensitive to atmospheric neutrinos.

## Summary

The data presented in this section demonstrate that the MINOS Far
Detector is capable of observing cosmic ray muon events and cosmic ray
neutrino events. These events are read out through the MINOS DAQ system.
They also show that all of the detector's 484 active planes are
sensitive to muons. Thus, this commissioning goal has been achieved.

# Neutrino Flux in the MINOS Near Detector

The NuMI beam produces a flux of neutrinos, some of which interact in
the MINOS Near Detector. The commissioning goal requires the detection
of these neutrinos.

During the NuMI commissioning run, charged-current neutrino events were
generated in the target region of the MINOS Near Detector.
Reconstruction of these events shows them to have momentum in the beam
direction and to occur in time with the beam pulse, thus tagging them as
beam-produced. The charged-current interaction rate is indicative of the
neutrino flux.

## Reconstruction of Charged-Current Events

Figure 6.21 is a Near Detector event display, which shows an event
collected during the NuMI commissioning run on January 21, 2005. The
absence of hits in the upstream planes indicates that the interacting
particle is neutral. The length of the penetrating track identifies it
as a muon with momentum in the beam direction. Thus, this event is
identified as a charged-current interaction from a beam-produced muon
neutrino.

![](media/image23.png){width="4.0625in" height="3.0347222222222223in"}

Figure 6.21 Event display of a charged-current event in the MINOS Near
Detector.

Consideration of the angular distribution and timing of the candidate
events demonstrates that they were produced by the NuMI beam.

### Angular Distribution of Near Detector Events

Beam-induced events in the Near Detector will have momentum in the
general direction of the beam. Figure 6.22 shows the distribution of
azimuth angle and zenith angle for data taken during the commissioning
run, superimposed on the distributions from cosmic rays. The red
histograms are candidate neutrino events only, the black histograms are
candidate neutrino events plus rock muons (muons produced by neutrino
interactions in the rock upstream) and the dotted histograms are cosmic
rays. The left-hand plot shows the distribution of zenith track angles.
Since the beam center passes through the Near Detector at a downward
angle of 3.3°, one would expect a typical cos θ value of approximately
0.06, which is consistent with the data. The right-hand plot shows the
azimuth angle distribution for the same events. The expected azimuth for
the beam direction is 154°. The neutrino and muon distributions are
clearly peaked in the beam direction. Both the zenith and azimuthal
angle distributions are markedly different from those induced by cosmic
rays, demonstrating that these are beam-induced events.

![](media/image24.png){width="6.002777777777778in"
height="3.0902777777777777in"}

Figure 6.22 Angular distributions of neutrino candidate events from the
NuMI commissioning run.

Figure 6.23 shows the distribution of the angle of event tracks with
respect to the calculated neutrino beam direction. The data include both
neutrino candidates and rock muons. The data collected during the
commissioning run are compared with the predictions of Monte Carlo
simulations run in the commissioning configuration, described in Section
7. The distribution is, to within the errors, what would be expected.

![](media/image25.png){width="5.002083333333333in" height="3.3875in"}

Figure 6.23 Distribution of track deviation (including rock muons) from
beam angle. Data are compared with Monte Carlo predictions for the
neutrino beam in the commissioning configuration.

### Timing of Near-Detector Events

The Near Detector collected data using a beam gate for a portion of the
NuMI commissioning run. The gate opened approximately 2 μs before the
anticipated start of the beam spill and remained open for a period of 18
μs. During this time, all data above a specified noise threshold were
read out from the detector. Figure 6.24 shows the time distribution of
energy in the detector, relative to the start of the beam gate, for a
total of 178 beam spills over 3 hours. The figure shows a low level of
noise throughout the gate. The 1.6 μs beam spill is clearly seen as the
enhancement of energy from 2 μs to 3.6 μs. All observed neutrino and
rock muon events in the detector occur during this time. The small tail
of energy visible for about 1 μs after the end of the beam spill is
likely due to neutrons produced in neutrino interactions.

![](media/image26.png){width="5.995138888888889in"
height="4.065972222222222in"}

Figure 6.24 Timing plot shows the Near Detector's ADC output *vs.* time.

## Charged-Current Event Rate in the MINOS Near Detector

During the NuMI commissioning run, five hours of data were recorded with
the proton beam centered on the NuMI production target. A total of 8.1 ×
10^14^ protons were delivered during this time, during which 49
charged-current neutrino events were observed in a 50-ton fiducial
volume. The fiducial volume is defined to be a cylinder extending from 1
m downstream of the front face of the detector to 1 m upstream of the
end of the calorimeter, 1 m in radius, centered on the intersection of
the beam center line with the front face of the detector. As trigger and
reconstruction efficiencies are not yet determined it is not possible to
state an absolute charged-current event rate. The analysis to determine
these efficiencies is presently underway.

## Summary

Both neutrino and rock muon events were observed in the MINOS Near
Detector during the commissioning run. The angular distributions and
timing of these events demonstrates that they were induced by the NuMI
beam. The number of charged-current events observed in the MINOS Near
Detector with the beam in the commissioning configuration is consistent
with expectations.

# Neutrino Beam Energy

The commissioning goal is to produce neutrinos with the beamline in the
low energy configuration. Such neutrinos typically have energies in the
2-4 GeV range.

In the NuMI beamline, the locations of the horns can be adjusted with
respect to the target location to change the energy profile of the beam.
The NuMI beam is presently in a "low energy" configuration, that is,
with a low-energy beam target in place and the horns in the proper
spacing for the NuMI low energy beam. The current run plan for MINOS is
to spend the majority of the run time in the low energy configuration,
which is designed to maximize the neutrino flux in the energy region
where the expected oscillation probability is highest. Within a given
horn configuration, the positioning of the target offers an additional
degree of freedom. During the commissioning of the beamline, data were
taken with the target pulled back 1 m relative to the normal low energy
position. This "pseudo-medium energy" variant of the low energy
configuration provides an increase in the overall neutrino flux. The
distribution of the energies of the muons from charged-current neutrinos
observed during the commissioning run is correlated to the neutrino
energies.

## Muon Track Energy

The energy of a muon from a charged-current interaction can be
determined from the range, based on the amount of material the muon
passed through before stopping. Figure 7.25 shows the energy for
fully-contained tracks in the Near Detector. The kinetic energy is
deduced from the amount of material through which the track passed. The
selected events met a track-length criterion (42 planes) to ensure a
minimum energy of 1.5 GeV. The dashed line shows the predicted muon
track energy spectrum for beam events. The energies observed in the data
are in good agreement with the prediction.

![](media/image27.png){width="3.9291666666666667in"
height="2.6791666666666667in"}

Figure 7.25 Distribution of muon energies in charged-current events
determined by muon range. Data taken during the commissioning run are
compared to Monte Carlo predictions for the NuMI beam in the
commissioning configuration.

## Summary

The muon energy distribution and the neutrino energy distribution that
it implies demonstrate that the NuMI beam produces neutrinos in the
energy range for which it is configured. The energy configuration will
be adapted to the region in which neutrino oscillations are most likely
to occur for the operational phase of the MINOS experiment.

# Conclusion

The preceding sections of this document have presented supporting
evidence for the successful completion of the NuMI Project. The NuMI
Project has achieved its commissioning goals as stated in Table 1.1 and
is now ready to request CD-4 from the Department of Energy. Upon
obtaining CD-4 the NuMI facility and the MINOS experiment are prepared
to enter their operational phase.