Missing ZDC EtSum TPs & L1TZDCEtSumsProducer Implementation

This article discusses the issue of missing ZDC EtSum Trigger Primitives (TPs) in the data and the implementation of the L1TZDCEtSumsProducer plugin to address this problem. This is a follow-up from issue #43214, where it was observed that some ZDC EtSum TPs were missing in certain events during the inclusion of ZDC EtSums in the L1T-emulation chain. This unexpected behavior was noted in 2024 PbPb data and data from the pO/OO/NeNe 2025 runs.

Background on the Issue

To give you guys a little background, the ZDC (Zero Degree Calorimeter) EtSum TPs are crucial components in the data acquisition system of the CMS experiment. These TPs provide essential information about the energy deposited in the forward region of the detector, which is vital for various physics analyses, especially in heavy-ion collisions. The missing TPs can lead to inaccuracies in the energy measurements, affecting the overall physics results. Therefore, identifying and resolving this issue is super important for the integrity of the data.

The problem was initially identified when integrating the ZDC EtSums into the Level-1 Trigger (L1T) emulation chain. During this process, it was noticed that some events were missing specific ZDC EtSum TPs. This was quite unexpected because these TPs should be present in every event. The issue was observed in data from the 2024 PbPb run and also in data from the planned pO/OO/NeNe 2025 runs, highlighting the broad scope of the problem. The detailed observations and initial discussions can be found in this GitHub issue.

Addressing the Missing TPs: The L1TZDCEtSumsProducer

To tackle the problem of these missing TPs, a solution was implemented through the L1TZDCEtSumsProducer plugin. This plugin was designed to recompute the EtSum values from the non-EtSum TPs in cases where the ZDC EtSum TPs were missing from an event. The updated implementation, which is part of pull request #48963, has been backported to the 14_1_X release series to ensure that the fix is applied across different versions of the software. Basically, this plugin acts as a safety net, ensuring that the EtSum values are still available even if the primary TPs are missing. This is a critical step in maintaining data quality and ensuring reliable physics analyses. The implementation involves reading the non-EtSum TPs and using them to derive the missing EtSum values. This process requires a solid understanding of the detector characteristics and the relationships between different TPs. The new implementation has undergone rigorous testing to ensure its accuracy and reliability. So far, the results look promising, but continuous monitoring and validation are essential.

Implementation Details of L1TZDCEtSumsProducer

The L1TZDCEtSumsProducer plugin works by recomputing the EtSum values from the available ZDC non-EtSum TPs. This involves a series of calculations and data manipulations to derive the missing EtSum values accurately. The plugin first checks for the presence of the ZDC EtSum TPs in an event. If these TPs are missing, the plugin then accesses the non-EtSum TPs. These non-EtSum TPs contain information that can be used to estimate the EtSum values. The plugin applies specific algorithms and calibrations to the non-EtSum TPs to calculate the EtSum values. These algorithms are based on a detailed understanding of the ZDC detector and its response to different types of particles. The recomputed EtSum values are then used in place of the missing ones, ensuring that the downstream analysis processes have the necessary data. The implementation includes error handling and validation steps to ensure the accuracy and reliability of the recomputed values. The plugin also logs any instances where the EtSum values are recomputed, which helps in monitoring the frequency and impact of the missing TPs. This detailed approach ensures that the data quality is maintained even in the absence of the primary EtSum TPs.

Impact and Benefits of the New Implementation

The implementation of the L1TZDCEtSumsProducer plugin has several significant benefits for the CMS experiment. Primarily, it ensures that the EtSum values are available for analysis even when the primary ZDC EtSum TPs are missing. This is crucial for maintaining data integrity and preventing data loss. By recomputing the EtSum values from the non-EtSum TPs, the plugin fills in the gaps and allows for accurate physics analyses. This is especially important in heavy-ion collisions, where the EtSum values are used to characterize the collision and select interesting events. The plugin also enhances the robustness of the L1T system. By providing an alternative source of EtSum values, it reduces the system's vulnerability to missing data. This is important for the overall stability and reliability of the experiment. The new implementation also simplifies the data processing workflow. By automatically handling the missing TPs, it reduces the need for manual intervention and data reprocessing. This saves time and resources, allowing the physics community to focus on scientific analysis. Furthermore, the plugin provides valuable diagnostic information. By logging instances where the EtSum values are recomputed, it helps in identifying and understanding the underlying causes of the missing TPs. This can lead to improvements in the detector hardware and data acquisition system.

The Underlying Issue and Future Steps

Despite the implementation of the L1TZDCEtSumsProducer, the root cause of the missing EtSum TPs remains unclear. The HCAL (Hadronic Calorimeter) team is expected to conduct a follow-up investigation to understand why these TPs are missing. The outcome of this investigation will be crucial in determining whether further improvements to the L1TZDCEtSumsProducer are needed. Basically, we need to figure out why these TPs are vanishing in the first place! Understanding the underlying issue is vital for a long-term solution. If the problem is related to the firmware version, for instance, the L1TZDCEtSumsProducer might need to handle the TPs differently based on the firmware version. This could involve implementing specific algorithms or calibrations for different firmware versions. On the other hand, if the issue is due to a hardware problem, it might require physical repairs or modifications to the detector. It’s also possible that the problem is a combination of hardware and software issues. The investigation will involve a detailed analysis of the data, as well as consultations with experts in the HCAL system and the L1T system. The goal is to gather as much information as possible to identify the root cause and develop an effective solution. Until the root cause is identified, the current implementation of L1TZDCEtSumsProducer is expected to provide a robust solution. However, further updates might be necessary depending on the investigation's findings. The collaboration and expertise of different teams are essential to address this complex issue. Regular updates and discussions are planned to ensure that everyone is informed and that the progress is tracked effectively. It's a collaborative effort to ensure the integrity and reliability of the CMS data.

Expected Outcome of the Investigation

The expected outcome of the HCAL investigation is to identify the root cause of the missing ZDC EtSum TPs. This will involve a thorough analysis of the data, the detector hardware, and the firmware. The investigation will likely include a review of the data acquisition system, the trigger system, and the calibration procedures. It may also involve simulations and modeling to understand the detector's behavior under different conditions. The investigation team will collaborate with experts from different areas, including detector experts, software engineers, and physicists. The goal is to gather all the necessary information to pinpoint the exact cause of the problem. Once the root cause is identified, a plan will be developed to address the issue. This may involve hardware repairs, firmware updates, software modifications, or a combination of these. The solution will be designed to prevent the missing TPs from occurring in the future and to ensure the accuracy and reliability of the data. The investigation will also assess the impact of the missing TPs on the physics analyses. This will help in determining the priority of the issue and the urgency of the solution. The results of the investigation will be documented in a report, which will be shared with the CMS collaboration. This will ensure that everyone is aware of the issue and the steps being taken to address it.

Potential Improvements to L1TZDCEtSumsProducer

Depending on the findings of the HCAL investigation, there are several potential improvements that could be made to the L1TZDCEtSumsProducer plugin. If the issue is related to the firmware version, the plugin might need to be updated to handle TPs differently based on the firmware version. This could involve implementing specific algorithms or calibrations for different firmware versions. For example, if a particular firmware version is known to have issues with the EtSum TPs, the plugin could use a different set of algorithms to recompute the EtSum values. Another potential improvement is to enhance the plugin's error handling capabilities. This could involve adding more detailed logging and error messages, which would help in diagnosing issues and monitoring the plugin's performance. The plugin could also be updated to handle different types of errors and exceptions more gracefully. If the investigation reveals that certain types of events are more prone to missing TPs, the plugin could be optimized to handle these events more efficiently. This might involve using different algorithms or calibrations for these events. The plugin could also be updated to take into account other relevant detector information, such as the detector's operating conditions and the beam conditions. This could help in improving the accuracy of the recomputed EtSum values. The goal is to make the plugin as robust and reliable as possible, ensuring that the EtSum values are always available for analysis.

Current Status and Expectations

Currently, the L1TZDCEtSumsProducer implementation is considered robust enough to handle the issue of missing TPs. However, we're keeping a close eye on things and are ready to make further updates if needed. The expectation is that the current implementation will provide a reliable solution while the investigation into the root cause is ongoing. The team is committed to maintaining the integrity and quality of the data. Regular monitoring and validation are being carried out to ensure that the plugin is performing as expected. The feedback from the physics community is also being taken into account, and any suggestions for improvements are being carefully considered. The goal is to ensure that the data is accurate and reliable, allowing for high-quality physics analyses. The collaboration between different teams is vital for addressing this issue effectively. Regular meetings and discussions are being held to keep everyone informed and to coordinate the efforts. The CMS collaboration is committed to addressing this issue and ensuring the success of the physics program. It’s a team effort to maintain the high standards of the experiment.

Collaboration and Communication

Effective collaboration and communication are crucial for addressing complex issues like the missing ZDC EtSum TPs. The team is actively collaborating with experts from different areas, including the HCAL team, the L1T team, and the data quality team. Regular meetings and discussions are being held to keep everyone informed and to coordinate the efforts. Communication channels, such as email lists and online forums, are being used to share information and updates. The team is also using issue tracking systems to manage tasks and track progress. Open and transparent communication is encouraged to ensure that everyone is aware of the issue and the steps being taken to address it. The feedback from the physics community is also being actively sought and taken into account. The goal is to foster a collaborative environment where everyone can contribute their expertise and ideas. The success of the project depends on the effective collaboration and communication between all the stakeholders. This collaborative approach ensures that the best solutions are developed and implemented. Regular updates are provided to the broader CMS collaboration to keep everyone informed about the progress and the outcomes. This transparency helps in building trust and confidence in the data quality and the analysis results.

Final Thoughts

In conclusion, the issue of missing ZDC EtSum TPs is a significant one that requires careful attention. The implementation of the L1TZDCEtSumsProducer plugin is a crucial step in addressing this problem, but understanding the underlying cause is equally important. The ongoing investigation by the HCAL team will be instrumental in determining the long-term solution. The collaboration and expertise of various teams within the CMS collaboration are essential to ensure the integrity and reliability of the data. We're all working together to make sure we get to the bottom of this and keep the data flowing smoothly. The commitment to high-quality data and accurate physics analyses remains the top priority. Continuous monitoring, validation, and collaboration will ensure that the experiment's goals are met and that meaningful scientific discoveries can be made. It’s a journey of continuous improvement and learning, and the CMS collaboration is well-equipped to tackle these challenges.

FYI: @JHiltbrand (HCAL), @BenjaminRS @quinnanm (L1T) - Thanks for your contributions and expertise! We appreciate your help in resolving this issue.