WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collections

Permanent URI for this collectionhttps://hdl.handle.net/20.500.13091/2

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Oncoidal Facies Across the Carboniferous-Permian Transition (Hadim Nappe, Southern Türkiye): Paleoenvironmental Implications and Correlations
(Wiley, 2025) Akbas, Melikan
The cortoid and/or oncoid-bearing carbonates of the Girvanella Limestone Facies of the Hadim Nappe that were deposited during the early-middle Gzhelian-middle Asselian time interval are represented by a succession that laterally extends over dozens of kilometres and is up to 60 m thick. This facies is easily distinguishable from the facies above and below and is considered a significant sedimentological marker unit by its lithological properties (e.g., brownish-red colour and large oncoids). Eight microfacies types are recognised from the Girvanella Limestone Facies: cortoid grainstone/floatstone, cortoid-bioclastic grainstone/rudstone, cortoid-aggregate grainstone, bioclastic grainstone to packstone, oncolite packstone/rudstone, oncoid grainstone/floatstone, mudstone/wackestone, and algal fenestral bindstone that are indicative of moderate to high-energy shallow marine carbonate platform settings (e.g., sand shoals and bank zone and lagoon-peritidal zone). Oncoid-bearing facies across the Carboniferous-Permian transition in the Hadim Nappe show a well correlation with similar deposits from South China, Iran, Mexico, Carnic Alps (Austria), and Japan. This widespread and synchronised deposition of the oncoid-bearing facies corresponds to the major phase (Glacial period III) of the Late Palaeozoic Gondwana glaciation and global sea-level drop associated with this glaciation.
Highly Effective Injection Composites With Fly Ash and Microsilica for Soil Stabilization
(MDPI, 2025) Ozkilic, Yasin Onuralp; Beskopylny, Alexey N.; Aksoylu, Ceyhun; Stel'makh, Sergey A.; Shcherban', Evgenii M.; Madenci, Emrah; Kosykh, Alexey
Injection composites based on mineral binders are widely used for soil stabilization, using jet grouting technology to solve various geotechnical problems. Cement, which contains toxic components and worsens the ecology of the environment, is typically the main mineral component used to manufacture injection composites. Reducing cement consumption in the production of building materials is currently of great importance. This study developed highly effective, environmentally friendly injection composites for soil stabilization based on three mineral components: Portland cement, fly ash (FA), and microsilica (MS). FA was introduced into the composites as a partial Portland cement substitute, in amounts ranging from 5 to 50% in 5% increments. The properties of fresh and hardened composites, including the density, flow rate, water separation, compressive strength at 7 and 28 days, and the structure and phase composition of the composites, were studied. The inclusion of FA in the composition of composites contributes to a decrease in density by 16.9%, from 1.89 g/cm3 to 1.57 g/cm3, and cone spread by 9%, from 30.1 cm to 27.4 cm, and an increase in water bleeding by 91.4%, from 3.5% to 6.7%, respectively. Based on the results of the experimental studies, the most effective dosage of FA was determined, which amounted to 20%. An increase in compressive strength was recorded for composites at the age of 7 days of 8.3%, from 33.6 MPa to 36.4 MPa, and for compressive strength at the age of 28 days of 9.4%, from 41.3 MPa to 45.2 MPa, respectively. SEM and XRD analysis results show that including FA and MS promotes the formation of additional calcium hydrosilicates (CSH) and the development of a compact and organized composite structure. The developed composites with FA contents of up to 50% exhibit the required properties and can be used for their intended purpose in real-world construction for soil stabilization.
Enhancing the Capacity of Wide-Span Steel Frames Using External Post-Tensioning Cables
(MDPI, 2025) Kocer, Mustafa; Sen, Huseyin
Steel portal frames are widely used in industrial buildings due to their high strength-to-weight ratio and rapid erection capability. However, many existing structures exhibit insufficient load-carrying capacity under current design requirements. This study investigates the use of external post-tensioning (PT) cables and rigid wedge anchorages to enhance the overall performance of steel portal frames. Two stages of numerical analysis were performed: (i) two-dimensional parametric studies to identify the most efficient configuration and (ii) three-dimensional verification under combined gravity, wind, and seismic loading conditions. Results show that the proposed PT system significantly increases the load-carrying capacity of both beams and columns, reduces bending demands, and improves global stability without major geometric modification. The strengthening method is safe, reversible, and offers a practical alternative to conventional welded or plated retrofit techniques.
Self-Powered Polyaniline/Si NIR Photodetectors for Waste Classification: Fabrication, Optimization, and Application
(American Chemical Society, 2025) Hussaini, Ali Akbar; Yilmaz, Kurtulus; Karaman, Mustafa; Yildirim, Murat
Rapid rise in the population and urbanization has led to increased waste generation, creating significant challenges for efficient waste management. Although recycling remains effective, manual sorting of diverse materials limits the scalability. In this study, we report the fabrication and optimization of polyaniline (PANI) interlayer-based photodetectors with varying film thicknesses by using plasma-enhanced chemical vapor deposition (PECVD). PANI films were characterized via UV-vis spectroscopy, FTIR, XPS, and AFM. Devices were tested under varying solar light intensities and a broad wavelength range (351-1600 nm). The photodetector with a 200 nm PANI layer exhibited the best performance, achieving a responsivity of 1.013 A/W, detectivity of 1.34 x 1011 Jones, and EQE of 114.2% under self-powered operation. We propose the use of this device for waste classification, shifting from conventional reflected NIR signal analysis to examining transmitted near-infrared (NIR) wavelengths through waste samples. Our results show that photocurrent, responsivity, and EQE from the PANI/n-Si heterojunction can reliably distinguish material types. This work demonstrates the potential of self-powered NIR photodetectors to enable automated, scalable, and efficient waste classification systems.
A Review of BLDC Motors: Types, Application, Failure Modes and Detection
(MDPI, 2025) Sen, Mehmet; Mutluer, Mumtaz
Brushless DC (BLDC) motors are widely used in many engineering fields such as transportation, industrial automation, pumping systems, household devices, and renewable energy applications. Their popularity mainly arises from advantages like high power density, low noise, long service life, and high efficiency. This study contributes to the literature by comprehensively addressing the types, applications, faults, and diagnostic methods of BLDC motors. This review systematically examines recent studies to identify and classify common mechanical, electrical, magnetic, thermal, and sensor-related faults. Diagnostic approaches reported in these studies are then analyzed and compared. The methods are grouped into several categories, including signal processing, model-based, data driven, artificial intelligence-supported, and thermal or magnetic monitoring techniques. The review results show that hybrid and intelligent diagnostic strategies, which combine different analysis methods, significantly improve the accuracy of fault detection and enable earlier fault identification. These improvements also contribute to higher reliability and safer operation of BLDC systems. In the discussion, attention is given to the growing use of artificial intelligence and data fusion in fault diagnosis. These trends are likely to guide the next generation of condition monitoring systems for BLDC motors. Overall, this study emphasizes the importance of developing reliable and sustainable diagnostic frameworks to enhance energy efficiency and system performance. The results can provide a useful reference for researchers and engineers working on BLDC motor technologies.
Effect of Rehabilitative Wall-Foundation Anchorage Types on the Seismic Behaviour of Weak Reinforced Concrete Frames
(MDPI, 2025) Yavuz, Gunnur; Kaltakci, M. Yasar
Installing shear walls in a load-bearing system is one of the most rational, economical, and effective strengthening methods for improving a building system that is vulnerable to seismic effects. One of the most significant points to consider in a reinforced concrete building strengthened with a shear wall is the sufficiency and reliability of anchorage elements in the shear wall-foundation joints, where significant bending moments will occur due to the impact of lateral loads. This study investigated the behaviour of different foundation anchorage methods, including internal anchorage (anchor bars) and external anchorage (steel angle and carbon-fibre-reinforced polymer (CFRP)) applied at the wall-foundation interface in retrofitted weak reinforced concrete frames, which were multi-span, multi-storey, lacking sufficient seismic detailing, and strengthened using wing-type shear walls, under quasi-static lateral loading. It was also aimed to determine the most effective anchorage method for improving the structural performance. A total of six undamaged, but seismically deficient, two-storey, two-span reinforced concrete frames were strengthened with added shear walls that incorporated different anchorage details at the shear wall-foundation joint. According to the test results, the addition of wing-shaped reinforced concrete rehabilitative walls significantly increased the lateral load-carrying capacity, lateral stiffness, and energy dissipation capacity of reinforced concrete frames with poor seismic behaviour. It was observed that additional strengthening was not required in the edge columns of frames with rehabilitative walls of a sufficient length, but that additional measures were required in the foundation anchors at the base of the strengthening wall due to the further increase in the rehabilitative wall capacity. Consequently, the most suitable shear wall foundation anchorage arrangement was achieved with test specimens where one internal anchor bar was used for each vertical shear reinforcement, independently of the shear wall length, and the development length was the highest.
The Influence of Fiber-Form Waste Tire Aggregates on the Flexural Strength, Ductility, and Energy Dissipation of Pultruded GFRP-Rubberized Concrete Hybrid Beams
(MDPI, 2025) Ecemis, Ali Serdar; Karalar, Memduh; Beskopylny, Alexey N.; Stel'makh, Sergey A.; Shcherban, Evgenii M.; Aksoylu, Ceyhun; Ozkilic, Yasin Onuralp
This study investigates the effects of different proportions of waste rubber fiber aggregates on the flexural behavior of reinforced concrete beams. Beam specimens were prepared with different proportions (5%, 10%, and 15%) of waste rubber fiber aggregates, and composite beams formed with pultruded GFRP profiles were tested under vertical load. According to the results of this study, cube compressive strength, cylinder tensile strength, and beam flexural strength decreased by 27.5%, 50%, and 47.6%, respectively, with the use of a 15% waste rubber aggregate. As a result of the four-point bending tests performed on reinforced concrete beams, the maximum load-carrying capacity of the beams decreased significantly after increasing the waste rubber aggregate ratio to 10% and 15%. However, a general improvement in the ductility of the beams was observed. One of the main results of this study is that when the waste rubber aggregate content is 5%, the best balance between strength and ductility is achieved, and the performance closest to the reference beams is obtained. The tests also revealed that the & Oslash;10-5% specimen exhibited higher performance in terms of both load-carrying capacity and yield stiffness. On the other hand, although the 15% waste rubber aggregate ratio caused a decrease in the maximum load-carrying capacity. along with an increase in the diameter of the tensile reinforcement, this decrease was quite low. Finally, an overall decrease in energy consumption capacity was observed with increasing waste rubber aggregate content in all test beams. This can be attributed to the acceleration of shear damage in the beam and the shrinkage of the area under the load-displacement curve as the amount of waste increases. Additionally, SEM analyses were conducted in order to investigate the microstructural behavior of the rubberized concrete. This study has shown that the use of waste rubber aggregates can be environmentally and economically beneficial, especially at the 5% level.
Investigation of Erosion Wear Behavior and Incubation Period of 3D-Printed ABS, PLA and Nylon-CF
(Emerald Group Publishing Ltd, 2025) Aydin, Mehmet Esat; Ozturk, Osman; Bagci, Mehmet
PurposeThis study aims to investigate the erosion wear behavior of three-dimensional (3D)-printed Acrylonitrile Butadiene Styrene (ABS), Polylactic acid (PLA) and Nylon-CF (Nylon Carbon Fiber) parts with jet impingement test using alumina (Al2O3) particles. The effects of build orientation and impingement angle on erosion wear behavior were investigated.Design/methodology/approachABS, PLA and Nylon test specimens with build orientations of 0 degrees, 45 degrees and 90 degrees were fabricated using a 3D printer. Erosion wear tests were conducted on these specimens at impingement angles of 30 degrees, 60 degrees and 90 degrees. The erosion wear rate was determined by measuring the weight loss. EDX analysis and SEM images were obtained to find the wear characteristics.FindingsThe build orientation affected the wear resistance of ABS slightly, whereas the orientation caused more significant differences in PLA and Nylon-CF. On the other hand, 90 degrees-oriented Nylon-CF composite gained mass, unlike other materials. From this point on, the incubation period specific to the composites was investigated by gradually increasing the amount of abrasive. The abrasive mass up to 5,000 g eventually finalized the incubation period and stabilized the weight loss of Nylon-CF. EDX results and SEM images were interpreted together, proving that the mass gain in Nylon-CF was due to the embedding of alumina particles in the matrix.Originality/valueThis study contributed to the literature to better understand the erosion wear behavior of the most used polymer-based materials produced with 3D printing. The incubation period detected in the Nylon-CF sample, which was found to be due to particle embedding, added another originality.
Aggloflotation of Bituminous Coal in a New Designed Cell
(Taylor & Francis Inc, 2025) Uslu, Nihat Yusuf; Duzyol, Selma
This study investigated the enrichment of high-ash bituminous coal by aggloflotation technique implemented within a new designed experimental cell. At the same time, this paper aimed to introduce the newly designed aggloflotation cell. This novel cell uniquely integrates the agglomeration and flotation processes into a single, unified unit, thereby simplifying the overall processing sequence. A coal sample, sourced from the Zonguldak & Ccedil;atala & gbreve;z & imath; coal preparation plant, was subjected to a series of tests under varied operational conditions including pH levels, agglomeration time, binder dosage, mixing speed, frother dosage, and dispersant. The performance of the aggloflotation process was evaluated by examining key metrics such as the concentrate's ash content, weight yield, and the combustible recovery. Notably, the experimental outcomes demonstrated that the new designed cell was efficient in processing ultra-fine bituminous coal in a single-stage operation. The process reduced the agglomeration time from 30 minute to just 5 minute, indicating substantial potential for both time and energy savings. Preliminary observations indicate that integrating both processes in one cell may also simplify process control. The outcomes suggest that this experimental setup represents a viable option for coal enrichment, inviting further investigation to determine its potential benefits.
Performance Analysis of RIS-Empowered OFDM-IM Communications under Weibull Fading and Joint Tx/Rx I/Q Imbalance
(TÜBİTAK Scientific & Technological Research Council Turkey, 2025) Ceniklioglu, Busra; Develi, Ibrahim; Canbilen, Ayse Elif
A modernist technique, reconfigurable intelligent surface (RIS) provides outstanding signal reflection and amplification, making it highly valuable for upcoming communication systems. Besides, a major contributor is index modulation (IM), attaining superior spectral and energy efficiency, and achieving hardware sufficiency. The primary and novel contribution of this work is the derivation of a highly accurate, closed-form approximate expression for the average bit error rate (ABER) of an orthogonal frequency division multiplexing (OFDM)-IM system operating in the complex and challenging environment characterized by joint transmitter/receiver (Tx / Rx ) in-phase and quadraturephase imbalance (IQI) and Weibull fading. This essential analytical achievement is facilitated by the newly formulated, closed-form pairwise error probability (PEP) expression specifically tailored to the maximum likelihood (ML) detector used in this non-ideal, effect of IQI on OFDM-IM system over the fading channel. Furthermore, this analysis is uniquely applied to quantify the precise performance impact of various RIS configurations under these simultaneous impairments. In addition the RIS configuration is shown to significantly enhance the overall system performance. Our results reveal that integrating RIS with OFDM-IM systems is an effective strategy to alleviate the undesirable impact of joint Tx and Rx IQI. The final and conclusive step of the work solidifies the analytical novelty by demonstrating that the derived closed-form ABER expressions are robust and accurate, as evidenced by the perfect match between the theoretical (analytical) results and the detailed Monte Carlo simulation results.
Kaolinite's Many Lives
(Nature Portfolio, 2026) Unal Ercan, Hatice
Nonlinear Finite Element Evaluation of the Seismic Performance of the Historic Ayvat Masonry Weir
(Springer, 2025) Mollamahmutoglu, Cagri; Ozturk, Mehdi; Aksoylu, Ceyhun; Madenci, Emrah; Ozkilic, Yasin Onuralp
A nonlinear seismic assessment of the 18th-century Ayvat masonry weir was performed by integrating three-dimensional finite-element (FE) modeling with Ground-Penetrating Radar (GPR) surveys. A detailed ABAQUS model of approximately 70000 continuum elements was developed and calibrated using laboratory-measured stone-mortar properties and GPR-derived foundation profiles. Nonlinear time-history analyses were carried out under Turkish Earthquake Code (TEC-2018) hazard levels DD1 (2%/50 yr) and DD2 (10%/50 yr) for both principal-axis and 45 degrees-rotated records. Under the 45 degrees-rotated DD1 record (EQ1R), crest-to-base displacements reached up to 0.30 m, and the isolated local maximum damage parameter (PEMAX*) reached 0.47. In contrast, under the 45 degrees-rotated DD2 record (EQ2R), maximum displacements remained below 0.01 m and PEMAX* did not exceed 0.14, thereby preserving global stability while inducing residual strains at the abutments. Stress concentrations were consistently detected at material discontinuities and joint zones. Based on these results, targeted retrofitting measures, including joint reinforcement and localized strengthening, are recommended to ensure the structural safety and preserve the heritage integrity of historic masonry weirs.
Advancing Remote Sensing with Few-Shot Learning: A Comprehensive Review of Methods, Challenges, and Future Directions
(Wiley, 2025) Aslan, Muhammet Fatih; Sabanci, Kadir; Durdu, Akif; Kaousar, Rehana
In this review, the details and developments of few-shot learning (FSL) techniques in different remote sensing (RS) studies including change monitoring, disaster management, urban monitoring, and agriculture are discussed in detail. Furthermore, a categorization is made by dividing FSL methods into three categories (metric-based, optimization-based, and transfer learning approaches) and considering hybrid approaches. Special attention is given to episodic training and meta-learning approaches that provide rapid adaptation to new classes with minimal examples. Furthermore, the integration of explainable artificial intelligence (XAI) and its real-time application capabilities are discussed. Important issues such as domain shift, class imbalance, and high dimensionality are discussed. Recent refinements such as task-level learning, data augmentation, and multimodal integration are examined. Finally, a coherent framework is suggested for further studies and practical FSL applications in the context of RS. As a result, it provides a more comprehensive perspective than previous reviews. This review aimed to guide future research in the integration of FSL with RS applications by analyzing the existing literature and pointing out important research gaps.
Ligand-Dependent Performance Optimization of CsPbX3/N-Si Schottky Photodiodes for Broadband Photodetection
(Springer, 2025) Varal, Nurhan Mehmet; Tok, Mutahire; Kirbiyik Kurukavak, Cisem; Durmus, Haziret; Kus, Mahmut
All-inorganic cesium lead halide perovskite nanoparticles (CsPbX3, X = Cl, Br) are promising candidates for optoelectronic devices due to their high absorption coefficients, narrow emission linewidths, and superior thermal stability compared to hybrid perovskites. In this work, Schottky photodiodes were fabricated on n-type Si substrates using CsPbBr3 and CsPbCl3 nanoparticle interlayers, both with native oleylamine/oleic acid ligands and after pyridine-based ligand exchange. Structural and morphological analyses via AFM revealed that pyridine treatment improved surface uniformity for CsPbBr3 films but induced aggregation in CsPbCl3 films. Electrical characterization using thermionic emission theory, Cheung's method, and Norde's method showed composition- and ligand-dependent variations in barrier height, series resistance, and ideality factors. Under varying illumination intensities, pyridine-treated CsPbBr3 devices (D2) exhibited over tenfold improvements in responsivity and detectivity compared to their untreated counterparts (D1), while pyridine-treated CsPbCl3 devices (D4) demonstrated high performance at low light intensities and maintained strong broadband detection from 351-1600 nm. CsPbCl3 devices with native ligands (D3) displayed unstable performance, excelling only in the long-wavelength infrared region (> 1400 nm). These results highlight the critical role of surface chemistry in tailoring perovskite-silicon photodiodes for broadband photodetection applications.
Optimum Location Selection for Photovoltaic Power Plants Based on Best-Worst Method: Example of Karatay District Konya, Türkiye
(Wiley, 2025) Aydin, Taha Kagan
Turkiye is a sunny region with very high potential for electricity generation from solar energy. This study identifies the most suitable areas for photovoltaic (PV) power plants in the Karatay district of Konya province using a combination of GIS (Geographical Information System) and the Best Worst Method (BWM). Based on the weighting of seven criteria (land use, proximity to existing transmission lines, proximity to residential areas, distance to the road network, slope, land aspect, elevation map), pairwise comparisons yielded a CR (xi*) of 0.0863514. The regional distribution of suitable areas was calculated as 16,982.87 ha (6.04%) very suitable, 68,516.53 ha (24.38%) suitable, and 31,147.46 ha (11.08%) less suitable, while 164,143.23 ha (58.41%) were unsuitable. The most influential criteria were land use (C1) and aspect (C6), with a weight value of 0.30 (30%). BWM enables two-sided comparisons using less data than other methods, increasing the reliability of results under uncertainty and producing more qualified outputs in location selection. The region's flat topography with high annual solar potential highlights the methodological novelty of the study. Elevation was the least effective factor, whereas land use was the most significant. Given the strong agricultural and livestock sectors, ensuring that PV facilities do not compromise these activities is critical, as establishing them on fertile lands may threaten food security and ecosystems. The quantified distribution of suitability classes and relative importance of criteria provide practical guidance for decision-makers (municipalities, private sector, energy investors, etc.), helping prioritize suitable areas while minimizing conflicts with agricultural and environmental values.
Multistage Evaluation of Strengthening Strategies for Achieving Adequate Seismic Performance in Reinforced Concrete School Buildings
(Elsevier Science Inc, 2026) Timurlenk, Piril; Uysal, Yusuf; Arslan, H. Derya; Arslan, M. Hakan
It is crucial that socially important structures, such as schools, remain operational without sustaining damage after earthquakes. However, some public buildings in Turkey have not received adequate engineering services, making it necessary to evaluate the seismic performance of these structures and apply appropriate strengthening methods when deemed necessary. This study comprehensively examines potential strengthening strategies and their effects on various school buildings in Turkiye, a country located in a highly active seismic zone with a vulnerable public building stock. Three commonly used school building types (8, 14, and 22 classrooms) were selected. Parametric studies were conducted on buildings with insufficient seismic performance, evaluating different strengthening scenarios. Input parameters included varying peak ground acceleration (PGA) values reflecting regional seismicity, diverse local soil conditions, and different material strengths. Strengthening strategies such as reinforced concrete jacketing, shear wall addition and FRP wrapping were applied to columns. A total of 432 structural models were analyzed. One or more of these methods were used to achieve the target performance level. Results were interpreted based on structural strength, period, over-strength factor and cost. It was found that the combination of shear wall addition and jacketing had the most significant impact on structural period, leading to notable reductions in spectral displacement demands. However, this combination also resulted in higher over-strength factors and increased strengthening costs compared to other methods. The study concludes that the absence of over-strength targets for retrofitted buildings in seismic codes is a critical gap and should be addressed in future code revisions.
ChatGPT as a Jury? Multi-Modal AI Versus Human Evaluation in an Architectural Design Competition
(Sage Publications Inc, 2025) Ozeren, Edibe Begum; Ozeren, Omer
This study examines the capacity of ChatGPT (GPT-4o), a large language model-based AI system, to evaluate architectural design competition projects. It investigates how jury input shapes the model's assessments and how effectively it integrates multimodal data (text + visuals). The analysis focuses on eight awarded projects (three prizes and five honorable mentions) from the 2025 Kad & imath;k & ouml;y Municipality New Service Building National Architectural Design Competition. ChatGPT assessed the projects under two scenarios: with access to jury reports (jury-influenced) and without any jury data (independent evaluation). In both cases, the projects were scored on a 0 to 5 scale across six thematic categories defined in the competition brief. The findings show that when jury reports were available, ChatGPT's evaluations aligned strongly with those of the human jury (r approximate to 0.87). Without jury input, project rankings and thematic emphases shifted, indicating the model's capacity to generate alternative interpretations based on textual and visual information. This study contributes to architectural evaluation research methodologically by introducing a dual-scenario framework, theoretically by revealing how AI mirrors or diverges from human judgment, and practically by demonstrating its potential as a decision-support tool. While AI can enrich evaluation processes, human expertise remains essential for nuanced, context-specific decision-making.
Search for CP Violation in Events with Top Quarks and Z Bosons at √s=13 and 13.6 Tev
(Elsevier, 2025) Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.; Sosnov, D.
A search for the violation of the charge-parity (CP) symmetry in the production of top quarks in association with Z bosons is presented, using events with at least three charged leptons and additional jets. The search is performed in a sample of proton-proton collision data collected by the CMS experiment at the CERN LHC in 2016-2018 at a center-of-mass energy of 13 TeV and in 2022 at 13.6 TeV, corresponding to a total integrated luminosity of 173 fb(-1). For the first time in this final state, observables that are odd under the CP transformation are employed. Also for the first time, physics-informed machine-learning techniques are used to construct these observables. While for standard model (SM) processes the distributions of these observables are predicted to be symmetric around zero, CP-violating modifications of the SM would introduce asymmetries. Two CP-odd operators O-Wt(I) and O-tZ(I) in the SM effective field theory are considered that may modify the interactions between top quarks and electroweak bosons. The obtained results are consistent with the SM prediction within two standard deviations, and exclusion limits on the associated Wilson coefficients of -2.7 < c(tW)(I) < 2.5 and -0.2 < c(tZ)(I) < 2.0 are set at 95% confidence level. The largest discrepancy is observed in CtZI where data is consistent with positive values, with an observed local significance with respect to the SM hypothesis of 2.5 standard deviations, when only linear terms are considered.
Observation of Λ Hyperon Local Polarization in P-Pb Collisions at √snn=8.16 Tev
(American Physical Society, 2025) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.; Bergauer, T.; Druzhkin, D.
The polarization of the Lambda and (Lambda) over bar hyperons along the beam direction has been measured in proton-lead (p-Pb) collisions at a center-of-mass energy per nucleon pair of 8.16 TeV. The data were obtained with the CMS detector at the LHC and correspond to an integrated luminosity of 186.0 +/- 6.5 nb(-1). A significant azimuthal dependence of the hyperon polarization, characterized by the second-order Fourier sine coefficient P-z,P-s2, is observed. The P-z,P-s2 values decrease as a function of charged particle multiplicity, but increase with transverse momentum. A hydrodynamic model that describes the observed P-z,P-s2 values in nucleus-nucleus collisions by introducing vorticity effects does not reproduce either the sign or the magnitude of the p-Pb results. These observations pose a challenge to the current theoretical implementation of spin polarization in heavy ion collisions and offer new insights into the origin of spin polarization in hadronic collisions at LHC energies.
Citation - Scopus: 2
Measurement of Light-By Scattering and the Breit-Wheeler Process, and Search for Axion-Like Particles in Ultraperipheral PbPb Collisions at √snn=5.02 TeV
(Springer, 2025) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Makarenko, V.
Measurements of light-by-light scattering (LbL, gamma gamma -> gamma gamma) and the Breit-Wheeler process (BW, gamma gamma -> e(+)e(-)) are reported in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV. The data sample, corresponding to an integrated luminosity of 1.7 nb(-1), was collected by the CMS experiment at the CERN LHC in 2018. Events with an exclusively produced gamma gamma or e(+)e(-) pair with invariant masses m(gamma gamma,ee) > 5 GeV, along with other fiducial criteria, are selected. The measured BW fiducial production cross section, sigma(fid)(gamma gamma -> e(+)e(-)) = 263.5 +/- 1.8(stat) +/- 17.8(syst) mu b, as well as the differential distributions for various kinematic observables, are in agreement with leading-order quantum electrodynamics predictions complemented with final-state photon radiation. The measured differential BW cross sections allow discrimination between different theoretical descriptions of the photon flux of the lead ion. In the LbL final state, 26 exclusive diphoton candidate events are observed compared with 12.0 +/- 2.9 expected for the background. Combined with previous results, the observed significance of the LbL signal with respect to the background-only hypothesis is above five standard deviations. The measured fiducial LbL scattering cross section, sigma(fid)(gamma gamma -> gamma gamma) = 107 +/- 24(stat) +/- 13(syst) nb, is in agreement with next- to-leading-order predictions. Limits on the production of axion-like particles coupled to photons are set over the mass range 5-100 GeV, including the most stringent limits to date in the range of 5-10 GeV.

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