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wimpmass [2009/05/08 17:36]
gunion |
wimpmass [2009/06/18 11:43] (current)
gunion |
| two decay chains. The strategy is to use mass | two decay chains. The strategy is to use mass |
| shell constraints and the measured missing transverse momenta to | shell constraints and the measured missing transverse momenta to |
| constrain the mass space. Depending on how many visible | constrain the mass space. The detailed method depends on the number of visible particles per decay chain. |
| particles per decay chain, the detailed method is different. | |
| |
| |
| When each decay chain contains three visible particles, the 4-momenta | When each decay chain contains three visible particles, the 4-momenta |
| of the missing particles, and therefore the masses of | of the missing particles, and therefore the masses of |
| all particles can be directly solved for by combining two events. The | all particles can be directly solved for by combining two events. The references are |
| references are | |
| |
| [[http://arxiv.org/abs/0802.4290|arXiv:0802.4290]] | [[http://arxiv.org/abs/0802.4290|arXiv:0802.4290]] |
| [[http://arxiv.org/abs/0905.1344|arXiv:0905.1344]] | [[http://arxiv.org/abs/0905.1344|arXiv:0905.1344]] |
| |
| The code for solving the system is {{:wimpmass.tar.gz|here}}. Use "tar -xvzf <filename>" to unzip. [[http://root.cern.ch/drupal/|ROOT]] is needed for | The code for solving the system is {{:wimpmass-1.00.tar.gz|here}}. Use "tar -xvzf <filename>" to unzip. [[http://root.cern.ch/drupal/|ROOT]] is needed for |
| compiling. See the "README" file for instructions on how to run the | compiling. See the "README" file for instructions on how to run the |
| code. A description on how to run a few examples is given [[wimpmass#how to run the examples|below]]. A Mathematica notebook used to symbolically reduce the equation system to a univariate polynomial equation is | code. A description of how to run a few examples is given [[wimpmass#how to run the examples|below]]. A Mathematica notebook used to symbolically reduce the equation system described in the above references to a univariate polynomial equation is |
| kept {{:solve3quad.nb.gz|here}} (This file only--remove the ".gz" extension before using it. It is not zipped. The extension is only used to avoid conflict with the Wiki), though it is not needed to run the code. | kept {{:solve3quad.nb.gz|here}} (To use this file only--remove the ".gz" extension before using it. It is not zipped. The extension is only used to avoid conflict with the Wiki); this mathematica notebook is not needed to run the main code --- it was simply used in constructing the final code. |
| |
| ==== (b) Two visible particles per decay chain ==== | ==== (b) Two visible particles per decay chain ==== |
| [[http://arxiv.org/abs/0810.5178|arXiv:0810.5178]] | [[http://arxiv.org/abs/0810.5178|arXiv:0810.5178]] |
| |
| We provide code that solve for the missing particles' momenta with | We also provide code that solves for the missing particles' momenta for given choices of the masses of the particles in the decay chain; this code is kept in |
| given masses, which is kept in | the {{:wimpmass-1.00.tar.gz|same place}} as (a), but the two can be compiled |
| the {{:wimpmass.tar.gz|same place}} as (a), but the two can be compiled | |
| independently, and ROOT is not needed in this case. See the "README" file for instructions on how to run the | independently, and ROOT is not needed in this case. See the "README" file for instructions on how to run the |
| code. A description on how to run a few examples is given [[wimpmass#how to run the examples|below]]. | code. A description on how to run a few examples is given [[wimpmass#how to run the examples|below]]. |
| |
| ==== (c) One visible particle per decay chain ==== | ==== (c) One visible particle per decay chain ==== |
| In this case, there are two unknown masses: the mass of the dark | In this case, there are two unknown masses: the mass of the dark |
| matter particle and that of its mother particle. The kinematic | matter particle and that of its mother particle. The kinematic |
| constraints divide the 2-dimensional masses space to an allowed region and a forbidden region, which are separated by the variable | constraints divide the 2-dimensional mass space into an allowed region and a forbidden region, which are separated by the variable |
| [[http://www.hep.phy.cam.ac.uk/~lester/mt2/index.html|"MT2"]]. See the following for a reference, which also | [[http://www.hep.phy.cam.ac.uk/~lester/mt2/index.html|"MT2"]]. See the following for a reference, which also |
| describes a fast algorithm for calculating MT2. | describes a fast algorithm for calculating MT2. |
| [[http://arxiv.org/abs/0810.5178|arXiv:0810.5178]] | [[http://arxiv.org/abs/0810.5178|arXiv:0810.5178]] |
| |
| The code for calculating MT2 using the algorithm is currently separate from those the cases (a) and (b), which is available | The code for calculating MT2 using the algorithm is currently separate from those for the cases (a) and (b); it is available |
| {{:mt2-1.01a.tar.gz|here}}. Please read the README file for usage. | {{:mt2-1.01a.tar.gz|here}}. Please read the README file for usage. |
| | |
| The essential code for (a) and (b) is located in the directory "WIMPMASS/src" after you download and unzip the source files. The files "topology22.cpp" and "topology33.cpp" correspond to the two topologies, which are given as subroutines without a "main" program. Examples of such main programs can be found in the "example" directory. To test these programs, you need to do the following (in a LINUX type environment with gcc installed): | The essential code for (a) and (b) is located in the directory "WIMPMASS/src" after you download and unzip the source files. The files "topology22.cpp" and "topology33.cpp" correspond to the two topologies, which are given as subroutines without a "main" program. Examples of such main programs can be found in the "example" directory. To test these programs, you need to do the following (in a LINUX type environment with gcc installed): |
| |
| 1. Download the source file {:wimpmass.tar.gz|wimpmass.tar.gz}}. Do "tar -xvzf wimpmass.tar.gz". A directory called "WIMPMASS" will be created. | 1. Download the source file {{:wimpmass-1.00.tar.gz|wimpmass-1.00.tar.gz}}. Do "tar -xvzf wimpmass-1.00.tar.gz". A directory called "WIMPMASS" will be created. |
| |
| 2. Assuming [[http://root.cern.ch/drupal/|ROOT]] is installed, go to the directory "WIMPMASS/src" and "WIMPMASS/examples", modify the Makefile to point to you ROOT directory. | 2. Assuming [[http://root.cern.ch/drupal/|ROOT]] is installed, go to the directory "WIMPMASS/src" and modify the Makefile in that directory to point to your ROOT directory. |
| | Then, go to the directory "WIMPMASS/examples" and modify the Makefile in this latter directory to point to your ROOT directory. |
| |
| 3. Go to the directory "WIMPMASS/", do "make". | 3. Go to the directory "WIMPMASS/", do "make". |
| |
| 4. Go to the directory "WIMPMASS/examples". There should be two executable files generated: "example22" and "example33", corresponding to the two topologies. Both of them read from an example LHE data file with a few events, call the corresponding routines and print out the solutions. "example22" solves for the missing particles' momenta with three trial masses, which can be changed in "example22.cpp" (look for "\\trial masses"). "example33" solves for the missing particles' momenta (and masses) by combining the first two events. | 4. Go to the directory "WIMPMASS/examples". There should be two executable files generated: "example22" and "example33", corresponding to the two topologies. Both of them read the first two events from an example LHE data file, call the corresponding routines and print out the solutions. |
| | |
| There is also an example in the MT2 package. It is straight forward to compile, which can be simply done by doing | "example22" assumes the presence of two identical chain decays of type Y -> b X -> b a N in each event, and solves for the invisible particles' (the two N's) momenta assuming three trial masses (m_Y,m_X,m_N), which can be changed in example22.cpp (look for comment "trial masses"). Depending on the input m_Y, m_X and m_N, there may be no solutions, one solution, or more than one solution. In this case, the two events are analyzed one at a time and solutions are returned provided the input visible momenta for the a,b of the two chains (contained in the example LHE data file) for a given event are consistent with there being choices for the invisible momenta consistent with the input assumed masses. The number of events being analyzed can be changed by altering the loop command below comment "loop over events". As the number of events is increased, the allowed region in m_Y,m_X,m_N space decreases and its structure can be analyzed following the procedures of the corresponding referenced papers to determine the actual masses. |
| | |
| | "example33" assumes the presence of two identical chain decays of type Z -> c Y -> c b X -> c b a N in each of a pair of events, and solves for the invisible particles' momenta (and common mass) for this event pair given the input visible momenta for the a,b,c particles in both events (six+six input visible momenta per pair). In this procedure, each pair of events yields as output the possible masses for the BSM particles (m_Z, m_Y, m_X and m_N) in the decay chain consistent with the input visible momenta and the presumed chain topology. Usually there is more than one possible solution. The number of events (n) employed can be increased by altering the command below comment "test the first pair of events". The number of event pairs that will be analyzed as n is increased is n(n-1)/2. For large n, the distributions of the number of solutions as a function of each of the masses develop peaks. After employing the techniques of the corresponding referenced papers, these peaks will be close to the actual masses of Z, Y, X and N. |
| | |
| | There is also an example in the MT2 package, which is straightforward to compile and run. To compile, do |
| |
| g++ -o example mt2_bisect.cpp example.cpp | g++ -o example mt2_bisect.cpp example.cpp |
| |
| or "make" using the provided Makefile (which simply contains the above command). | or “make” using the provided Makefile (which simply contains the above command). The executable “example” calculates MT2 for an example event, which is given in the file “example.cpp”. |
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