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John Campbell

Publications and source records attributed to John Campbell.

At least 19 recordsLinked to original sources
arXiv2026

The Ramanujan Challenge For AI

To help evaluate the mathematical skills of current AI systems, we present a set of formulas for fundamental mathematical constants. These problems are attractive for AI evaluation because they are concrete and can be checked numerically to arbitrary precision, yet proving them may require non-obvious mathematics. Mathematical constants such as $π$, $e$, Catalan's constant, and special values of the Riemann zeta function have fascinated mathematicians for centuries. The search for formulas evaluating mathematical constants has produced some of the most beautiful mathematics in the field, especially in cases that yield irrationality proofs or fast convergence rates. Ramanujan's legacy is emblematic of this tradition. The list we provide contains two types of problems: formulas whose proofs are known to the authors but will remain encrypted for a short initial period; and formulas that are not yet proven. We are curious to see the achievements of AI in both cases.

math.HO↗
arXiv2024

Projection-to-Born-improved Subtractions at NNLO

While the current frontier in fixed-order precision for collider observables is N$^3$LO, important steps are necessary to consolidate NNLO cross-section predictions with improved stability and efficiency. Slicing methods have been successfully applied to obtain NNLO and N$^3$LO predictions, but have shown poor performance in the presence of fiducial cuts due to large kinematical power corrections. In this paper we implement Projection-to-Born-improved $q_T$ (P2B $q_T$) and jettiness (P2B $τ_0$) subtractions for a large class of color singlet processes in MCFM. This method allows for the efficient evaluation of \emph{fiducial} power corrections in any non-local subtraction scheme using a Projection-to-Born subtraction. We demonstrate the significant numerical improvements of this method based on fiducial Drell-Yan and Higgs cross-sections. Moreover, with fiducial power corrections removed via this method, the leading-logarithmic power corrections that have only been calculated without fiducial cuts can be included, further improving the calculations. For di-photon production with photon isolation, we devise a novel method in combination with P2B-improved subtractions, which we name $P2B_γ$ $τ_0$, and $P2B_γ$ $q_T$ for the two subtraction schemes, respectively. This method allows the inclusion of both fiducial power corrections due to kinematic cuts on the photons and a set of isolation power corrections in the fragmentation channel where a quark may enter the isolation cone. We find significant improvements in the convergence of NNLO di-photon cross-sections with photon isolation cuts, demonstrating that it is possible to achieve a stable and efficient calculation of di-photon cross-sections using slicing methods.

hep-ph↗
arXiv2023

Third order QCD predictions for fiducial W-boson production

Measurements of W-boson production at the LHC have reached percent-level precision and impose challenging demands on theoretical predictions. Such predictions directly limit the precision of measurements of fundamental quantities such as the W-boson mass and the weak mixing angle. A dominant source of uncertainty in predictions is from higher-order QCD effects. We present a calculation of W-boson production at the level of $α_s^3$ at fixed order and including transverse-momentum resummation. We further show predictions for a direct comparison with low-pileup ATLAS transverse-momentum and fiducial cross-section measurements at $\sqrt{s}=5.02\text{ TeV}$. We discuss in detail the impact of modern PDFs. Our calculation including the matching to W+jet production at NNLO will be publicly available the upcoming CuTe-MCFM release and allows for theory-data comparison at the state-of-the-art level.

hep-ph↗
arXiv2022

Series acceleration formulas obtained from experimentally discovered hypergeometric recursions

In 2010, Kh. Hessami Pilehrood and T. Hessami Pilehrood introduced generating function identities used to obtain series accelerations for values of Dirichlet's $β$ function, via the Markov--Wilf--Zeilberger method. Inspired by these past results, together with related results introduced by Chu et al., we introduce a variety of hypergeometric recurrences. We prove these recurrences using the WZ method, and we apply these recurrences to obtain series acceleration identities. We introduce a family of summations generalizing a Ramanujan-type series for $\frac{1}{π^2}$ due to Guillera, and a family of summations generalizing an accelerated series for Catalan's constant due to Lupaş, and many related results.

math.CO↗
arXiv2022

Fiducial Drell-Yan production at the LHC improved by transverse-momentum resummation at N$^4$LL+N$^3$LO

Drell-Yan production is one of the precision cornerstones of the LHC, serving as calibration for measurements such as the $W$-boson mass. Its extreme precision at the level of 1% challenges theory predictions at the highest level. We present the first independent calculation of Drell-Yan production at order $α_s^3$ in transverse-momentum ($q_T$) resummation improved perturbation theory. Our calculation reaches the state-of-the-art through inclusion of the recently published four loop rapidity anomalous dimension and three loop massive axial-vector contributions. We compare to the most recent data from CMS with fiducial and differential cross-section predictions and find excellent agreement at the percent level. Our resummed calculation including the matching to $Z$+jet production at NNLO is publicly available in the upcoming CuTe-MCFM 10.3 release and allows for theory-data comparison at an unprecedented level.

hep-ph↗
arXiv2022

Measuring Discrepancies in Airbnb Guest Acceptance Rates Using Anonymized Demographic Data

In order to make technological systems and platforms more equitable, organizations must be able to measure the scale of potential inequities as well as the efficacy of proposed solutions. In this paper, we present a system that measures discrepancies in platform user experience that are attributable to perceived race (experience gaps) using anonymized data. This allows for progress to be made in this area while limiting any potential privacy risk. Specifically, the system enforces the privacy model of p-sensitive k-anonymity to conduct measurement without ever storing or having access to a 1:1 mapping between user identifiers and perceived race. We test this system in the context of the Airbnb guest booking experience. Our simulation-based power analysis shows that the system can measure the efficacy of proposed platform-wide interventions with comparable precision to non-anonymized data. Our work establishes that measurement of experience gaps with anonymized data is feasible and can be used to guide the development of policies to promote equitable outcomes for users of Airbnb as well as other technology platforms.

stat.AP↗
arXiv2021

Testing parton distribution functions with t-channel single-top-quark production

The production of single top-quarks in the t-channel at hadron colliders imposes strong analytic constraints on parton distribution functions (PDFs) through its double deeply inelastic scattering (DDIS) form. We exploit this to provide novel consistency checks between LO, NLO and NNLO PDF fits and propose to include it as a constraint in future PDF fits. Furthermore, while it is well-known that the b-quark PDF is highly sensitive to the b-quark mass, we show that the treatment of this systematic uncertainty is still incomplete, fragmented or outright missing at the moment. Consequently, we conclude that the b-quark mass uncertainty is the dominant but so far broadly neglected theory uncertainty for this process.

hep-ph↗
arXiv2021

HL-LHC Computing Review Stage-2, Common Software Projects: Event Generators

This paper has been prepared by the HEP Software Foundation (HSF) Physics Event Generator Working Group (WG), as an input to the second phase of the LHCC review of High-Luminosity LHC (HL-LHC) computing, which is due to take place in November 2021. It complements previous documents prepared by the WG in the context of the first phase of the LHCC review in 2020, including in particular the WG paper on the specific challenges in Monte Carlo event generator software for HL-LHC, which has since been updated and published, and which we are also submitting to the November 2021 review as an integral part of our contribution.

hep-ph↗
arXiv2021

Single-top-quark production in the $t$-channel at NNLO

We present a calculation of t-channel single-top-quark production and decay in the five-flavor scheme at NNLO. Our results resolve a disagreement between two previous calculations of this process that found a difference in the inclusive cross section at the level of the NNLO coefficient itself. We compare in detail with the previous calculations at the inclusive, differential and fiducial level including b-quark tagging at a fixed scale $μ=m_t$. In addition, we advocate the use of double deep inelastic scattering (DDIS) scales ($μ^2=Q^2$ for the light-quark line and $μ^2=Q^2+m_t^2$ for the heavy-quark line) that maximize perturbative stability and allow for robust scale uncertainties. All NNLO and NLO$\,\otimes\,$NLO contributions for production and decay are included in the on-shell and vertex-function approximation. We present fiducial and differential results for a variety of observables used in Standard Model and Beyond Standard Model analyses, and find an important difference between the NLO and NNLO predictions of exclusive $t+n$-jet cross sections. Overall we find that NNLO corrections are crucial for a precise identification of the t-channel process.

hep-ph↗
arXiv2019

Precision phenomenology with MCFM

Without proper control of numerical and methodological errors in theoretical predictions at the per mille level it is not possible to study the effect of input parameters in current hadron-collider measurements at the required precision. We present a new version of the parton-level code MCFM that achieves this requirement through its highly-parallelized nature, significant performance improvements and new features. An automatic differential cutoff extrapolation is introduced to assess the cutoff dependence of all results, thus ensuring their reliability and potentially improving fixed-cutoff results by an order of magnitude. The efficient differential study of PDF uncertainties and PDF set differences at NNLO, for multiple PDF sets simultaneously, is achieved by exploiting correlations. We use these improvements to study uncertainties and PDF sensitivity at NNLO, using 371 PDF set members. The work described here permits NNLO studies that were previously prohibitively expensive, and lays the groundwork necessary for a future implementation of NNLO calculations with a jet at Born level in MCFM.

hep-ph↗
arXiv2017

Interference in the $gg\rightarrow h \rightarrow γγ$ On-Shell Rate and the Higgs Boson Total Width

We consider interference between the Higgs signal and QCD background in $gg\rightarrow h \rightarrow γγ$ and its effect on the on-shell Higgs rate. The existence of sizable strong phases leads to destructive interference of about 2% of the on-shell cross section in the Standard Model. This effect can be enhanced by beyond the standard model physics. In particular, since it scales differently from the usual rates, the presence of interference allows indirect limits to be placed on the Higgs width in a novel way, using on-shell rate measurements. Our study motivates further QCD calculations to reduce uncertainties. We discuss potential width-sensitive observables, both using total and differential rates and find that the HL-LHC can potentially indirectly probe widths of order tens of MeV.

hep-ph↗
arXiv2016

WW + jet at 14 and 100 TeV

In the current LHC run, an accurate understanding of Standard Model processes is extremely important. Processes including electroweak gauge bosons serve as standard candles for SM measurements, and equally constitute important backgrounds for Beyond-the-Standard Model (BSM) searches. We present here the next-to-leading order (NLO) QCD virtual contributions to W+W- + jet in an analytic format obtained through unitarity methods. We present results for the full process using the Monte Carlo event generator MCFM, and discuss total as well as differential cross-sections for the LHC with 14 TeV center-of-mass energy, as well as a future 100 TeV proton-proton machine.

hep-ph↗
arXiv2016

Quantitative Analysis of Desirability in User Experience

The multi-dimensional nature of user experience warrants rigorous assessment of the interactive experience in systems. User experience assessments are based on product evaluations and subsequent analysis of the collected data using quantitative and qualitative techniques. The quality of user experience assessments are dependent on the effectiveness of the techniques deployed. This paper presents the results of a quantitative analysis of desirability aspects of the user experience in a comparative product evaluation study. The data collection was conducted using 118 item Microsoft Product Reaction Cards (PRC) tool followed by data analysis based on the Surface Measure of Overall Performance (SMOP) approach. The results of this study suggest that the incorporation of SMOP as an approach for PRC data analysis derive conclusive evidence of desirability in user experience. The significance of the paper is that it presents a novel analysis method incorporating product reaction cards and surface measure of overall performance approach for an effective quantitative analysis which can be used in academic research and industrial practice.

cs.CY↗
arXiv2016

Towards an Understanding of Valence in E-Government Services

The Australian government, to remind job seekers of appointments with employment services providers in order to cut costs and free up human resources, is using technologies such as Short Messaging Services (SMS). However, the technologies in-use are but one side of this equation the specifics of how these technologies are used is the other side, and these specifics are highly under-theorized, particularly in regard to the views of the people to which these technologies are directed. The purpose of this paper is to provide a theoretical framing for this phenomenon as well as to introduce an emerging methodological direction that may allow for a better understanding of demographic-specific values and thereby better valence framing. The paper also theorizes reactions to information that could be applicable elsewhere, not just in e-government or with SMS, thereby contributing to discussions surrounding the Big Data debate.

cs.CY↗
arXiv2016

W+W- + jet: compact analytic results

In the second run of the LHC, which started in April 2015, an accurate understanding of Standard Model processes is more crucial than ever. Processes including electroweak gauge bosons serve as standard candles for SM measurements, and equally constitute important background for BSM searches. We here present the NLO QCD virtual contributions to W+W- + jet in an analytic format obtained through unitarity methods and show results for the full process using an implementation into the Monte Carlo event generator MCFM. Phenomenologically, we investigate total as well as differential cross sections for the LHC with 14 TeV center-of-mass energy, as well as a future 100 TeV proton-proton machine. In the format presented here, the one-loop virtual contributions also serve as important ingredients in the calculation of W+W- pair production at NNLO.

hep-ph↗
arXiv2013

Single top production in association with a Z boson at the LHC

We present results for the production of a Z boson in association with single top at next-to-leading order (NLO), including the decay of the top quark and the Z boson. This electroweak process gives rise to the trilepton signature l+l-l'+- + jets + missing energy. We present results for this signature and show that the rate is competitive with the contribution of the mixed strong and electroweak production process, ttZ. As such it should be observable in the full data sample from LHC running at $\sqrt{s}=8$ TeV. The single top + Z process is a hitherto unconsidered irreducible background in searches for flavour changing neutral current decays of the top quark in tt production. For a selection of cuts used at the LHC involving a b-tag it is the dominant background. In an appendix we also briefly discuss the impact of NLO corrections on the related tH process.

hep-ph↗
arXiv2010

Quantum Darwinism as a Darwinian process

The Darwinian nature of Wojciech Zurek's theory of Quantum Darwinism is evaluated against the criteria of a Darwinian process as understood within Universal Darwinism. The characteristics of a Darwinian process are developed including the consequences of accumulated adaptations resulting in adaptive systems operating in accordance with Friston's free energy principle and employing environmental simulations. Quantum theory, as developed in Zurek's research program and encapsulated by his theory of Quantum Darwinism is discussed from the view that Zurek's derivation of the measurement axioms implies that the evolution of a quantum system entangled with environmental entities is determined solely by the nature of the entangled system. There need be no further logical foundation. Quantum Darwinism is found to conform to the Darwinian paradigm in unexpected detail and is thus may be considered a theory within the framework of Universal Darwinism. With the inclusion of Quantum Darwinism within Universal Darwinism and the explanatory power of Darwinian processes extended beyond biology and the social sciences to include the creation and evolution of scientific subject matter within particle physics, atomic physics and chemistry, it is suggested that Universal Darwinism may be considered a candidate 'Theory of Everything' as anticipated by David Deutsch.

physics.gen-ph↗