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Questions tagged [data-analysis]

Use for question relating the the techniques of data analysis.

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1answer
42 views

Double slit experiment/ fitting data to complicated sine function and vice versa [closed]

As part of analysing the double slit experiment, I've recorded position values for a number of minima and the central peak position. Also, I've conducted a single slit experiment (with unknown width)...
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2answers
52 views

Removing zero-counts in exponential decay measurement

I'm doing an experiment where I'm measuring the mean-lifetime of muons. I have a set of data points for the number of decays against time, resembling an exponential distribution (of course). But in ...
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0answers
60 views

Where to find databases from physics experiments?

In some lecture I want to write about data analysis in physics I want to show some real uses of data analysis tools in the analysis of data from real experiments. I tried to search but I couldn't find ...
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1answer
30 views

What do the points on a Dalitz plot represent

I have read that a Dalitz plot is nothing but the plot of $m_{12}^2$ vs $m_{23}^2$, and that the dots correspond to "events". However, this doesn't really tell me anything. My question can boil down ...
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2answers
69 views

Estimate of the period of noisy “event counting” data

I have a set of experimental data, which come from a periodical event. More specifically, these are detections from a single photon detector, so there is no intensity, I only have the timestamps of ...
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0answers
31 views

Data-analysis (Uncertainty and errors)

This is just a data anlysis question but I thought you might need an introduction. In order to calibrate de Michelson interferometer one needs to find $\eta$ in the relation: $d = \eta D_\mu$ where $...
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1answer
32 views

File with particle decay data [closed]

Does anyone know of a computer parsable file that has basic physics and decay data for (quite many) observable particles, such as mesons, barions, heavy leptons and $W, Z, H$? To clarify the data I ...
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0answers
19 views

Does the vertex efficiency include track reconstruction efficiency?

Consider a document of ATLAS collaboration on displaced vertex level efficiency. On the first two pages there is a description of cut-offs required to background free displaced vertex reconstruction. ...
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1answer
48 views

What is the significance of a $\chi^2$ analysis?

What is the merit of $\chi^2$ analysis in the laboratory experiments? Why is so much emphasis put on it?
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1answer
202 views

Binning or just skipping values in a simulation to avoid autocorrelation

Given a set of data from a generic Montecarlo simulation $x_i$, $(1=1,...,N)$, autocorrelation is expected to happen between data points within relaxation time $\tau$ (correlation time) distance ...
3
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1answer
87 views

Jackknife estimation of variance very different from expected variance

I was rapidly introduced to the Jackknife procedure for data analysis and I stumbled upon a problem I'm not able to understand. Let's consider a very simple case: the estimation of the average of a ...
2
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2answers
77 views

Is there any experiment that doesn't have a finite countable number of outcomes?

There are a lot of random variables in physics that are, in principle, continuous and unbounded (canonical examples: time, position along each direction). In practice, it is my understanding that the ...
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0answers
74 views

Exclusion limits on particle dark matter

I'm trying to make sense on how the upper limits of the cross section of particle dark matter (WIMPs) are computed, like in the figure below. This is taken from an article on dark matter searches. ...
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1answer
43 views

Determining Threshold Voltage and Plateau from experimental data

I’ve been trying to figure out how to interpret the following data from the Geiger muller tube There are only seven data points. Where does the plateau begin? Has the data collection begun after the ...
0
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1answer
32 views

Tracking efficiency for experiments at CERN

For various experiments (e.g. ALICE, CMS etc) at the CERN-LHC, people talk about tracking efficiency. What exactly is this tracking efficiency? How different is it from reconstruction efficiency?
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1answer
68 views

Convergence tests for experimental data

I ran a simulation for the critical density at which traffic flow transitions from laminar flow to start-stop-waves. The results for different road lengths are: From the graph we can see that the ...
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0answers
38 views

Question about statement of uncertainty

I have a doubt about uncertainty of a measurement. I have a sample of a specific material which is my reference material and it is calibrated and NIST traceable. This sentence is in its data-sheet: ...
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0answers
62 views

What are common methods to remove discretization on experimental measures?

I have some experimental data, and since the measurements are digital, the data is discretized/quantized/rounded/truncated. I need to know if there are general methods, or common methods, to "smooth" ...
4
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1answer
103 views

What causes the 20 second period in LIGO data?

I download LIGO data on GW150914 (gravitational waves) via the code in Mathematica ...
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0answers
507 views

Parallel Axis Theorem Experiment

I am currently working on a physics experiment to confirm the parallel axis theorem. To do this, I have the following setup: In this experiment I change the distance between the centre of the ...
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1answer
452 views

Moment of Inertia and Mass Experiement

I am currently working on a physics project to experimentally confirm the relationship between mass and moment of inertia. The experiment is setup as depicted: In this experiment, $r1$ and $r2$ are ...
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0answers
47 views

Correlations and associativity

Suppose one has a set of data $D$ and a theoretical model $M(A,B,C)$ one wants to fit to it by obtaining the best fitting values of the parameters $A,B,C$, which in principle are free. Plotting the ...
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1answer
28 views

How to find average in this case?

If we have 10 trials of measuring density each repeated three times. How can we find average? Do we take the average of each trial and then find the average of the averages? Would this be physically ...
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0answers
35 views

Uncertainty of interpolation when covariance matrix is given

Assume that there is a given covariance matrix of an evaluated quantity ( in my case it's a rection cross section $\sigma = f(E)$, where $\sigma$ is the cross section and $E$ is each energy point ...
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3answers
302 views

Uncertainty in counting population? Vs uncertainty in measuring length?

I know that when I use a ruler to measure the length of a table, an uncertainty will be the finite width of the ruler's markings. What about when counting people? Say I count the number of people ...
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2answers
76 views

Consistency of data

In particle physics, what factors do we consider to conclude that the measurements done by two different experiments are consistent with each other? (You may even explain the concept with an example)
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2answers
59 views

Experiment on friction coefficient

Here you can see the results of the experiment about a friction coefficient: The mean of the friction coefficient becomes 0.262 but when I do a linear regression in the form of y=mx the slope is 0.31....
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2answers
103 views

How to analyse gamma ray spectra?

I have recently done an experiment using gamma radiation and am now at a loss as to how to analyse the data I acquired. I have a background spectrum and a spectrum from a radioactive sample and need ...
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0answers
45 views

Can a particle be identified when one knows $\left<dE/dx\right>$ and the Cherenkov angle $\theta_c$?

I have a question about if it would be possible to identify a particle by measuring the energy loss due to ionization $\langle dE/dx\rangle$ and the Cherenkov angle $\theta_c$. I assume that we know ...
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2answers
48 views

How does finding the $y$-intercept of a graph reduce error compared to finding the average of the data set?

In my particular case I have the equation $$ \frac{1}{d_i} = -\frac{1}{d_o}+\frac{1}{f} $$ and I'm plotting $\frac{1}{d_i}$ against $\frac{1}{d_o}$ to give an intercept of (in theory) -1 and a $y$-...
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1answer
81 views

Difference between Fourier and Laplace transforms in analyzing data

I have a set of displacement-time graphs from an experiment to convert to the frequency domain. Both the Fourier and Laplace transform seem to do this, so what's the difference between them (...
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0answers
59 views

What “error” should we report? The standard deviation of the mean or twice the standard deviation of a single measurement?

According to some sources, when one performs $N$ independent measurements of a Gaussian-like distributed values, one should report the mean value $\pm \text{the uncertainty}$ where the uncertainty is ...
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2answers
107 views

Reporting an uncertainty lower than the precision of the apparatus?

When performing $N$ independent measurements following a Gaussian distribution, it is sometimes said to report the mean and the standard deviation of the mean as value and its uncertainty. Now, the ...
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1answer
197 views

When to round off standard deviations in uncertainty propagation?

Let's take a concrete example. One is dealing with a wire through which a DC is running. One measures its voltage and obtain its current by measuring the magnetic field around it in some way such that ...
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1answer
214 views

What do we mean by fit of data in particle physics?

I am unable to clearly understand the meaning of fitting the data. Like in this paper of determination of mass and width of Z boson and number of neutrinos (from ALEPH detector) Does it mean that ...
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1answer
27 views

Reason for borexino pep flux confidence level error

At the TAUP conference in 2011, the Borexino collaboration presented an analysis of electron-neutrino elastic scattering events in their liquid scintillation detector to claim the first observation of ...
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1answer
196 views

Analyzing the rates of cooling points using the graph and data [closed]

how should i use this data to analyse the differences between the two materials. and what calculations could i use for it?
3
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1answer
133 views

What is the difference between data-driven and semi-data-driven techniques?

I keep hearing the terms data-driven and semi-data-driven techniques(especially for background estimation) in many CERN analysis talks. I looked for their difference but didn't find any documentation ...
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1answer
276 views

How to estimate the goodness of a 2D fit using the chi-square distribution?

I have measured a quantity $b$ as a function of two variables, let's say $x$ and $y$. Then I fitted a 2D polynomial of the shape $$b(x,y) = \sum c_{j,i} x^i y^j$$ to the data (which is of 2nd order). ...
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1answer
205 views

What is meant by “decay topology” in experimental high energy physics

Often we come across 'decay topology' while doing data analysis in experimental particle physics. My guess is that it represents decay of a particle and how it decays and into what it decays. Edit: I ...
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3answers
74 views

Describe the dynamics of a fluctuating vector

I have a time series for the $\mathbf{v}(t) = (x,y,z)$ components of a vector quantity. It is fluctuating in time, and has a non-trivial autocorrelation function which I want to somehow elucidate. The ...
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1answer
83 views

Question when comparing two experimental results

In my textbook it says that if two experimental results vary less than 3$\sigma$ then they can be considered to have arrived at the same result. My question is how do you determine this "x$\sigma$". ...
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1answer
55 views

What is the actual significance of increasing efficiency of a detector?

Say, I have a gamma detector with a 80% detection efficiency. And I buy a new one, with 85% efficiency, or even 90%. How exactly does it benefit me to be having 10% greater efficiency, other than to ...
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0answers
28 views

Is there a mathematical model that models spectral power distribution curves?

The experiment was aimed to find the specturm cruve of different light bulbs experimentally. Is there a mathematical way to justify the results I obtained (the plotted graph)? Would the equation in ...
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1answer
41 views

Is it valid to compare experimental data and theoretical data like this? Does the vertical axis of the graphs have to correspond?

The plotted curve is the experimental value of the SPD curve. Though it doesn't look "spikey" as it should, stacking the image on top seems to explain that the data is infact correct, but that more ...
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0answers
77 views

Calculation of mixing angle and mass squared difference in neutrino experiments

How is an exclusion curve/contour plotted in $\Delta{m^2}$ - $\tan(\theta)$ plane from a given experimental data and how the best fit value of $\Delta{m^2}$ (mass squared difference) and $\theta$ (...
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0answers
29 views

Statistical test to determine agreement between measurements

I'm in the following situation: I have the results from a one factor experiment in which I measured using instrument A, and I wish to compare them to the results obtained by using instrument B (same ...
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5answers
3k views

How do scientists determine when to disregard a model that has a higher correlation to data than another model?

For any set of data points, you can comprise a 100% correlated and fitted curve using a sum of sloped lines all multiplied by their respective Heaviside step functions to form a zig-zag shaped curve. ...
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1answer
782 views

What are signal efficiency and background rejection?

Recently I came across the terms signal efficiency and background rejection (for example in this paper), but I couldn't find an understandable definitions to those terms and how they are used. ...
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1answer
92 views

Selection criteria in experimental particle physics

I often read in particle physics articles, "relaxed selection criteria" and "nominal selection criteria" of events. what is the meaning of relaxed and nominal ? PS : Links and details would be ...