REVIEW
Top quark mass measurements at and above threshold at CLIC
High Energy Physics - Experiment · Submitted 15 Mar 2013 · 45 references
Pith's verdict: A careful full-simulation CLIC study whose above-threshold result holds up; the 34 MeV threshold number is a toy closure resting on a flat efficiency measured at one energy, and that gap is the one the authors don't flag.
T0 · AI review
Why Pith says this
Highlight any text to comment on it.
Referee report
The paper
The paper claims
A simulated 500 GeV CLIC stage could pin the top quark mass to roughly 100 MeV, and the threshold scan does it in a mass scheme that theory can actually interpret.
The reading
What carries the argument
Two pieces of machinery carry the argument. The first is the kinematic fit: it enforces three-dimensional energy and momentum conservation including the beam crossing angle, fixes both $W$ masses to 80.4 GeV, and forces the top and anti-top masses to be equal, varying jet and lepton four-momenta within their measured resolutions; this both sharpens the mass distribution and rejects more than 97 percent of the $qbar{q}$ background. The second is the threshold template fit: the top-pair cross section near threshold is computed with the TOPPIK code at next-to-next-to-leading order in the 1S mass scheme, folded with initial-state radiation and with the machine's luminosity spectrum, and the simulated data points are compared against a grid of templates in mass and $alpha_{s}$ spaced by 50 MeV and 0.0007 respectively. The luminosity spectrum is the pivot of the comparison with ILC: beamstrahlung smears the threshold rise, so the shape of that spectrum is itself a systematic input to the mass.
Extended reading notes
Core claim
The central claim is that a 500 GeV CLIC stage with 100 inverse femtobarns delivers a top quark mass with a total uncertainty around or below 100 MeV by two independent routes, and that the threshold route is the one with a defensible theoretical interpretation. Above threshold, a kinematic fit imposing energy-momentum conservation, the nominal $W$ mass of 80.4 GeV, and equal masses for top and anti-top, followed by a binned-likelihood background rejection, yields clean fully-hadronic and semi-leptonic samples; an unbinned fit of a Breit-Wigner convolved with a three-Gaussian resolution function and a background tail gives $m_{t} = 174.133$ GeV with a combined statistical error of 80 MeV and a width of $1.55$ GeV with an error of 220 MeV. At threshold, ten energy points spaced by 1 GeV from 344 to 353 GeV, 10 inverse femtobarns each, are fitted against NNLO cross-section templates in the 1S scheme, giving a statistical mass error of 34 MeV and a strong coupling error of 0.0009, with a theory normalization uncertainty worth only 5 to 8 MeV on the mass. Repeating the threshold analysis with the ILC luminosity spectrum, which has a sharper main peak, tightens the statistical error to 27 MeV, a difference far below the systematic uncertainties.
Load-bearing premise
The threshold-scan precision rests on the assumption that the signal selection efficiency of 70.2 percent and the residual background cross section of 73 femtobarns, both measured from fully simulated events at a single energy of 352 GeV, stay constant across the entire 344 to 353 GeV scan range, even though near threshold the event kinematics and the kinematic-fit success rate change quickly with energy.
Editorial extensions
If this is right
- A threshold scan at a linear collider would deliver the top mass in the 1S scheme, which can be converted into other mass conventions, unlike the generator mass extracted from invariant-mass reconstruction.
- The same scan determines the strong coupling to about 0.0009, comparable to the current world-average uncertainty, so $alpha_{s}$ need not be taken as an external input.
- Because the direct-reconstruction and threshold masses would be measured at the same machine, their difference becomes a handle on non-perturbative and colour-reconnection effects in the invariant-mass interpretation.
- The comparison of CLIC and ILC luminosity spectra shows the sharper ILC peak buys only about 20 percent in statistical precision, so the choice between technologies is not decided by the threshold-scan mass error.
- A ten-point scan of 100 inverse femtobarns total would already be limited by systematics rather than statistics, with the luminosity-spectrum shape the largest single worry.
- A six-point scan from 344 to 349 GeV, 60 inverse femtobarns, degrades the mass error to 40 MeV and the coupling error to 0.0013, showing the region above threshold matters mainly for $alpha_{s}$.
Reading between the lines
- The paper's two numbers point in opposite directions for strategy: the 80 MeV invariant-mass result is cheaper in luminosity but currently unusable for precision physics, while the 34 MeV threshold result is only meaningful if the machine's luminosity spectrum is known to better than roughly 20 percent in RMS width, so accelerator diagnostics become a physics deliverable.
- If the flat-efficiency assumption across the scan range fails, the distortion enters as a shape change in the cross-section rise, which is degenerate with a mass shift; a single additional simulated point at 344 GeV would test this cheaply.
- The 350 MeV shift from a 2 percent b-jet energy scale error, versus under 100 MeV from light jets, suggests the b-jet calibration programme (using $Z \to b\bar{b}$ in di-boson and radiative-return events) is the binding experimental systematic for the above-threshold measurement.
- A future comparison of a threshold-scan 1S mass with a hadron-collider Monte Carlo mass would test the size of the non-perturbative correction directly, rather than inferring it from generator comparisons.
Original abstract
We present a study of the expected precision of the top quark mass determination, measured at a linear e+ e- collider based on CLIC technology. GEANT4-based detector simulation and full event reconstruction including realistic physics and beam-induced background levels are used. Two different techniques to measure the top mass are studied: The direct reconstruction of the invariant mass of the top quark decay products and the measurement of the mass together with the strong coupling constant in a threshold scan, in both cases including first studies of expected systematic uncertainties. For the direct reconstruction, experimental uncertainties around 100 MeV are achieved, which are at present not matched by a theoretical understanding on a similar level. With a threshold scan, total uncertainties of around 100 MeV are achieved, including theoretical uncertainties in a well-defined top mass scheme. For the threshold scan, the precision at ILC is also studied to provide a comparison of the two linear collider technologies.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We present a study of the expected precision of the top quark mass determination, measured at a linear e+ e- collider based on CLIC technology. GEANT4-based detector simulation and full event reconstruction including realistic physics and beam-induced background levels are used. Two different techniques to measure the top mass are studied: The direct reconstruction of the invariant mass of the top quark decay products and the measurement of the mass together with the strong coupling constant in a threshold scan, in both cases including first studies of expected systematic uncertainties. For the direct reconstruction, experimental uncertainties around 100 MeV are achieved, which are at present not matched by a theoretical understanding on a similar level. With a threshold scan, total uncertainties of around 100 MeV are achieved, including theoretical uncertainties in a well-defined top mass scheme. For the threshold scan, the precision at ILC is also studied to provide a comparison of the two linear collider technologies.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present a study of the expected precision of the top quark mass determination, measured at a linear e+ e- collider based on CLIC technology. | contribution 1.00 | 0.81 | 0.06 | asserted 0.91 |
| s1 | GEANT4-based detector simulation and full event reconstruction including realistic physics and beam-induced background levels are used. | method 1.00 | 0.79 | 0.02 | asserted 0.99 |
| s2 | Two different techniques to measure the top mass are studied: The direct reconstruction of the invariant mass of the top quark decay products and the measurement of the mass together with the strong coupling constant in a threshold scan, in both cases including first studies of expected systematic uncertainties. | method 0.65 | 0.80 | 0.08 | asserted 0.96 |
| s3 | For the direct reconstruction, experimental uncertainties around 100 MeV are achieved, which are at present not matched by a theoretical understanding on a similar level. | result 0.93 | 0.76 | 0.18 | asserted 1.00 |
| s4 | With a threshold scan, total uncertainties of around 100 MeV are achieved, including theoretical uncertainties in a well-defined top mass scheme. | result 1.00 | 0.82 | 0.34 | asserted 1.00 |
| s5 | For the threshold scan, the precision at ILC is also studied to provide a comparison of the two linear collider technologies. | contribution 0.90 | 0.78 | 0.04 | asserted 0.92 |
What was examined, and what was not
- arXiv listing abstract v3
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
Figures
Showing 6 of the paper's 7 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:1303.3758 by the authors.
References
How later papers used it
56 later papers cite it
2 later papers by other authors are listed below: 1 used its method or tool and 2 used its data or values. 1 of them appears under more than one label. 3 more papers by the same authors are listed: 1 built on it, 3 used its method or tool and 1 used its data or values. 2 of them appear under more than one label.
Builds on it 1 of 2 papers with this label · 1 by the same authors
By the same authors
-
Extended the analysis discussed in detail in this paper to provide a first look at the impact of the NNNLO scale uncertainties on the top quark mass measurement in a threshold scan.
A First Look at the Impact of NNNLO Theory Uncertainties on Top Mass Measurements at the ILC (2016) (same authors) · 1.00 · paraphrased: the licence does not allow quoting
Uses its method or tool 4 of 7 papers with this label · 3 by the same authors
-
Performed a fit to the cross-section measurement according to the method proposed in this paper, using a predefined function obtained from the double-top calculation at NNLO.
Study of single top production at high energy electron positron colliders (2014) · 1.00 · paraphrased: the licence does not allow quoting
By the same authors
-
Combined the results of NNNLO QCD calculations with the experimental techniques developed in this paper to perform a first preliminary analysis of the impact of scale uncertainties on the top mass extraction.
A First Look at the Impact of NNNLO Theory Uncertainties on Top Mass Measurements at the ILC (2016) (same authors) · 0.86 · paraphrased: the licence does not allow quoting
-
Corrected its theory cross section for initial state radiation and for the luminosity spectrum of the collider as described in this paper.
Scanning Strategies at the Top Threshold at ILC (2019) (same authors) · 0.99 · paraphrased: the licence does not allow quoting
-
Used the methodology described in this paper with state-of-the-art NNNLO QCD calculations of ttbar production as input to account for the ILC luminosity spectrum, initial state radiation, signal efficiencies and background contributions.
The Potential of the ILC for Discovering New Particles (2017) (same authors) · 0.99 · paraphrased: the licence does not allow quoting
Uses its data or values 3 of 10 papers with this label · 1 by the same authors
-
Expected an 18 MeV variation in the extracted top-quark mass for a 5% shift of the estimated background contribution, citing this paper.
Optimising top-quark threshold scan at CLIC using genetic algorithm (2021) · 0.93 · paraphrased: the licence does not allow quoting
-
Followed the energy range and top quark mass choices in this paper.
Study of single top production at high energy electron positron colliders (2014) · 0.87 · paraphrased: the licence does not allow quoting
By the same authors
-
Assumed a signal efficiency of 70.2% for the cross section measurement, with an effective background level after all selection cuts of 73 fb, following this paper.
Scanning Strategies at the Top Threshold at ILC (2019) (same authors) · 0.98 · paraphrased: the licence does not allow quoting
How the literature uses it
56 arXiv papers cite this in 101 sentences
Papers whose main result relates to this one's
States the same result 1 paper
-
A careful analysis suggests that the top quark mass can be extracted from a threshold scan at NLC with an accuracy of about 100 MeV.
Papers citing it · 70 sentences without a confident label
Builds on it 2 papers
-
To provide a first look at the impact of the NNNLO scale uncertainties on the measurement of the top quark mass in a threshold scan, the analysis discussed in detail in [ref] has been extended, as discussed in the following.
A First Look at the Impact of NNNLO Theory Uncertainties on Top Mass Measurements at the ILC · A threshold scan analysis with NNNLO scale uncertainties · 1.00
-
In this contribution, the analysis described in [ref] is extended to two-dimensional extractions of the top quark mass and width and of the mass and the Yukawa coupling.
Scanning Strategies at the Top Threshold at ILC · Introduction · 1.00
Uses its method or tool 7 papers
-
Here, the results of these calculations are combined with the experimental techniques developed in [ref] to perform a first preliminary analysis of the impact of the scale uncertainties on the top mass extraction.
A First Look at the Impact of NNNLO Theory Uncertainties on Top Mass Measurements at the ILC · Introduction · 0.86
-
The present study builds on the technique developed in [ref] , obtaining simulated cross section measurements from a combination of the NNNLO top pair production cross section with the signal reconstruction efficiencies and expected background levels from full detector simulations performed slightly above the top pair production threshold.
Scanning Strategies at the Top Threshold at ILC · The simulation study · 0.84
-
According to the method proposed in [ref] , a fit is performed to the cross-section measurement, using a predefined function obtained from the double-top calculation at NNLO.
Study of single top production at high energy electron positron colliders · Analysis of top mass at threshold · 1.00
Uses its data or values 10 papers
-
Following [ref] , a signal efficiency of 70.2% is assumed for the cross section measurement, with an effective background level after all selection cuts of 73 fb.
Scanning Strategies at the Top Threshold at ILC · The simulation study · 0.98
-
When generating simulated measurements (pseudo-data), the overall top-pair event reconstruction efficiency of 70.2% (including the relevant branching fractions) was assumed, and the background contribution remaining after the event selection procedure corresponding to the cross section of 73 fb [ref] .
Optimising top-quark threshold scan at CLIC using genetic algorithm · Reference scenario · 1.00
-
In summary, for a 300 fb$^-1$ threshold scan, the total expected uncertainty on the top quark mass is $∼100$ MeV, resulting from the sum in quadrature of the following contributions: a statistical uncertainty of order 30 MeV (from Ref. [ref] , confirmed to be possible also with 100 fb$^-1$ from a 2-parameter fit in a recent study in Ref. [ref] ), 35 MeV (beam energy), 50 MeV (luminosity spectrum) and 80 MeV (from the conversion of $s_res$ into $m_t$ according Eq. [ref]).
Determination of the top quark mass circa 2013: methods, subtleties, perspectives · Threshold $tt̅$ production at $e^+e^-$ colliders: experimental simulations · 0.87
Compares with it 2 papers
-
This uncertainty is comparable in size to the uncertainty derived for a naive 3% scale uncertainty in the theory in [ref] .
A First Look at the Impact of NNNLO Theory Uncertainties on Top Mass Measurements at the ILC · Systematic uncertainties derived from scale variations · 0.99
-
As data events are recorded at the most efficient single energy point, 7 MeV statistical uncertainty can be achieved within 50 $fb^-1$ effective integrated luminosity, which is about half of that comparing to the 10 average distributed points scheme used in [ref] with an equal total integrated luminosity.
An optimal scheme for top quark mass measurement near $t\bar{t}$ threshold at future $e^{+}e^{-}$ colliders · Summary · 1.00
Cites it as support 1 paper
-
In the context of Higgs boson and top quark physics, this is for example beneficial for the rejection of physics background in hadronic and semi-leptonic final states, for the kinematic reconstruction of particle masses and for the constraints on the jet energy scales, as shown for top quark pair events in [ref] .
Higgs and top physics reconstruction challenges and opportunities at FCC-ee · Particle flow and beyond : reconstructing individual particles, jets, and global event kinematics · 1.00
Cites it as background 4 papers
-
Actually, relative studies [ref] have already been made to simulate the threshold scan at future $e^+e^-$ colliders.
An optimal scheme for top quark mass measurement near $t\bar{t}$ threshold at future $e^{+}e^{-}$ colliders · Top mass measurement scheme · 0.95
-
Recent reanalyses include realistic beam energy spectra for the ILC and CLIC [ref] and beam polarization [ref] .
Study of single top production at high energy electron positron colliders · Analysis of top mass at threshold · 0.87
-
The CLIC has been extensively studied for interactions beyond the SM [ref] .
Probe of electromagnetic moments of the tau lepton in gamma-gamma collisions at the CLIC · Introduction · 0.94
What it cites · 6 sentences without a confident label
Uses the method or tool of 1 paper
-
For the present analyses, the 500 GeV version of the CLIC_ILD [ref] detector is used.
Physics and Detectors at CLIC: CLIC Conceptual Design Report · Experimental conditions and detectors at CLIC · 0.96
Uses data or values from 1 paper
-
However, an additional systematic uncertainty of 20 MeV on the mass arises from the precision of $α_s$, when assuming the current uncertainty of the world average of 0.0007 [ref] .
World Summary of $\alpha_s$ (2012) · Alternative scenarios · 1.00
Cites as background 2 papers
-
More information on the beam induced backgrounds can be found in [ref] .
Physics and Detectors at CLIC: CLIC Conceptual Design Report · Event generation, simulation and reconstruction · 0.92
-
The project is foreseen to be implemented in several stages [ref] to provide optimal luminosity conditions at lower energies.
The CLIC Programme: Towards a Staged e+e- Linear Collider Exploring the Terascale : CLIC Conceptual Design Report · Experimental conditions and detectors at CLIC · 0.88
Discussion
Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.